NORTH LAWRENCE WATERSHED DRAINAGE STUDY
TABLE OF CONTENTS
EXECUTIVE
SUMMARY
I.
Introduction
A.
Watershed
Description
B.
Purpose
C.
Scope of
Project
II.
Public
Involvement
A.
Key
Stakeholder Interviews
B.
Area
Business and Resident Survey
C.
Public
Drop-In Center
D.
Lawrence Planning Commission Update
III.
Ultimate
Land Use for Watershed
A.
Key
Land Use Assumptions
B.
City Input
C.
Mapping
Results
IV. Data Collection
A.
Field
Investigation
B.
Surveys
C.
GIS Mapping
V. Internal
Drainage System Analysis
A.
General
Methodology
B.
Findings
and Recommendations
1.
System 1
2.
System 2
3.
System 3
4.
System 4
5.
System 5
6.
System 6
7.
System 7
8.
System 8
9.
System 9
10. System 10
11. System 11
12. System 12
C.
System
Naming Convention
D.
Hydrologic
and Hydraulic Analyses
1.
Hydrologic
Parameters
2.
Hydraulic
Parameters
VI. Watershed Analysis
A.
Overview
B.
Recommendations
C.
HEC-1
Model Development
1. General Project Information
2. Data and Model Development
3. Input Parameter Development
4. Naming Conventions
5. Hydrologic Methodology
6. Model Comparison
D.
HEC-RAS
Model Development
1.
General Project Information
2.
Data Sources
3.
Input Parameter Development
4.
Results
E.
Alternatives for Future Development
1.
Flood
Reduction Alternatives
2.
Future Hydraulic Drainage
Improvements
3.
Summary
VII. Kansas
River Floodplain Analysis
A.
Purpose
B.
Results
C.
HEC-RAS Model
Development
1. General Project Information
2. Data Sources
3. Input Parameter Development
EXECUTIVE
SUMMARY
I.
Introduction
The
City of Lawrence has embarked on a program to develop a
stormwater management plan for the North Lawrence watershed. This program
is based on a recognized need to upgrade existing facilities to modern design
standards and to provide coordinated facilities in developing areas. The
economic well being of the City depends on
its ability to attract and retain business and industry, as well as residents
to live in the City. Part of the City’s ability to attract businesses and residents depends on its ability
to provide adequate services such as drinking water, sewers, transportation and
stormwater management. With the ever expanding urban area and associated
increases in impervious surfaces such as parking lots, the frequency with which
drainage issues occur appears to be increasing. This has caused the City to focus its attention on the need to provide adequate stormwater
management policies and infrastructure in all areas within the watershed.
The North Lawrence Drainage Study is one important step in this process.
The
North Lawrence Drainage Study was divided into two main focus areas. The
Internal System consists of the City operated
ditches, pipes, and pumps within the existing City boundaries. The overall watershed analysis modeled the less
developed drainage aspects of the North Lawrence Drainage Area. More
detailed descriptions of the two focus areas can be found later in the report.
II. Recommendations
A. Overall Watershed
Several
alternatives were investigated in the overall North Lawrence Drainage Study
watershed to reduce flood elevations, lessen impacts on the “Internal Drainage
System” facilities, provide drainage in the event of high flows on the Kansas
River, and assess the effects of development in the floodplain. The
investigations led to the four major recommendations below. The first
bullet item is the key to reducing the burden on the Internal System from areas
beyond the existing city limits.
- Drainage from north of 24/40 Highway should be
cutoff by the highway embankment and the water should be pumped over the
levee at a point just east of the 24/40 intersection to reduce the burden
on the 2nd Street Pump Station
- Future development in the watershed should
maintain the current conveyance levels in the 100-year floodplain –
development should not reduce the capacity for floodplain storage
- The City should purchase parcels of land as necessary
for use as dedicated ponding areas
- Major roads and hydraulic structures should be
improved to meet the current APWA criteria with regard to overtopping
during the 100-year event, in order to provide adequate emergency services
to the area
A cost summary with regard
to these Watershed Analysis recommendations is shown in the table on the next
page.
![](N_Law_Drainage_Study_2005_files/image001.gif)
B. Internal System
Analyses
for the Internal Drainage System provided areas of concern throughout the City operated drainage network. The excess peak flow was used to
represent the degree to which a conduit is undersized for the ultimate
build-out condition. Each investigated lateral flowing into the main stem
of a system and each main stem conduit were ranked by excess peak flow.
This led to the following priority listing of recommended improvements.
Prioritization of Internal Systems
|
Link Name
|
Excess Peak Flow
|
Total Estimated Cost of Improvements
|
(cfs)
|
(dollars)
|
S1-1
|
315
|
$9,163,000
|
S6-1
|
168
|
$3,994,000
|
S9-1
|
133
|
$1,132,000
|
S1L1-1
|
96
|
$333,000
|
S1L5-1
|
85
|
$235,000
|
S1L7-1
|
85
|
$59,000
|
S1L3-1
|
56
|
$187,000
|
S6L3-1
|
56
|
$195,000
|
S6L3-7D
|
New pipes
|
$181,000
|
S4-1
|
43
|
$60,000
|
S6L2-1
|
37
|
$5,000
|
S4L4-1
|
35
|
$53,000
|
S4L2-1
|
27
|
$36,000
|
S9L1-1
|
21
|
$7,000
|
S1L2-1
|
20
|
$240,000
|
S8-1
|
17
|
$115,000
|
S10L2-1
|
13
|
$4,000
|
S7-1
|
13
|
$38,000
|
S5-1
|
10
|
$56,000
|
S10-1
|
6
|
$106,000
|
S1L4-1
|
1
|
$7,000
|
S1L6-1
|
0
|
$0
|
S11-1
|
0
|
$0
|
S3-1
|
0
|
$0
|
S2-1
|
0
|
$0
|
S12-1
|
0
|
$0
|
Total
|
|
$16,206,000
|
The
flows calculated in the analysis of the internal system assume that the cutoff
north of 24/40 Highway, as recommended by the Watershed Analysis, is in
place. However, the costs in the table for the Internal System Analysis
are independent of the costs for the Watershed Analysis improvement
recommendations. By adding the total costs from each of the two summary
tables, the estimated cost of all recommendations is approximately $41 million.
As
with the overall watershed, a viable option within the internal system is land
purchase. In areas that naturally drain to a low point, it is often
advantageous to preserve the ponding area by
purchasing the parcel of land. Those costs are included in several of the
system costs in the table.
III. Background
A. Watershed Description
The
North Lawrence watershed is estimated to be 9,100 acres generally bordered by
the Kansas River levee on the south and the Mud Creek levee on the east. Most of the drainage contributes to the
Maple Grove system, which either conveys water south to the City or east eventually to Mud Creek. A few areas near the levee, to the northwest and southeast,
drain directly to the Kansas River, while a thin strip of land along part of
the northeastern portion of the watershed flows directly to Mud Creek. Refer to the North Lawrence Drainage Study map in Section I
of the main report for an overview of the project area.
The
Kansas River floodplain completely encompasses North Lawrence. The
natural silt loam soils are highly permeable. However, increased
development is replacing those soils with nearly impermeable clay material in
certain areas. In addition, extremely mild slopes across the landform
cause frequent ponding and roadway overtopping.
Historically, North Lawrence has been an agricultural community with low
density residential development. Pockets of commercial and industrial
development now appear in areas of the watershed. While parts of North
Lawrence will likely remain agricultural, the projected future land use in other
areas will add more and more impervious surfaces.
B. Purpose
The
Lawrence-Douglas County Planning Commission proposed this study to address repeated flooding concerns from
residents of the North Lawrence area. Flooding problems occur in a number
of areas within the North Lawrence watershed. The major causes are as
follows:
- Development that has significantly increased
runoff from design storm events
- Undersized drainage system components such as
culverts, drainage channels, underground pipe systems and inlets
- Siltation within the storm drainage system
- Past development of flood-prone areas
- A shallow, flat and interrupted watershed
drainage network
Public comments relating to
current drainage issues, proposed developments, long-range plans, and
floodplain regulations are at the root of this study. The purpose of this
study is to identify areas with flooding problems, analyze the major elements
of the storm drainage system with respect to long-term land use, and recommend
needed improvements to correct or prevent systems from flooding. By doing
this, proposed developments and long-range plans will be influenced. At
the same time, regulations can be conceptualized to avoid potential pitfalls.
C.
Scope of Project
The
North Lawrence Drainage Study has several major components which work toward
the generation of system requirements for stormwater conveyance and
infrastructure in the ultimate buildout
scenario. The following major tasks were included in the study:
- Integration of the public involvement program
that gathered and used information from residents, business owners and
property owners when considering alternatives or upgrades within the
watershed
- Estimation of the ultimate land use for the
watershed
- Survey and general inspection of the drainage
system
- Development of a digital database that shows the
existing components of the City’s
drainage system
- Evaluation of the internal drainage system for
the ultimate buildout scenario and
recommendation of improvements
- Evaluation of the watershed drainage system for
the ultimate buildout scenario and
recommendation of improvements
- Completion of an analysis of Kansas River
flooding resulting from levee overtopping
Along with the recommended
improvements, the magnitude of the costs required to implement them were
assessed. It should be noted though, that detailed design of the projects
recommended in this report is required to produce proper construction documents
and accurate cost estimates for system components.
The
main body of the project report is divided up into seven sections.
Summaries of the various sections are detailed below. For a detailed
description of the methods or results of each section, refer to the main
report.
IV. Public Involvement
The
North Lawrence Drainage Study public involvement program was designed to
establish meaningful and useful dialogue between stakeholders, businesses,
residents in the area and the study team. A series of outreach efforts
were conducted to catalogue and assess the public’s concerns. Members of
the project team provided an overview of study activities and public input to
the Lawrence Planning Commission.
V. Ultimate Land Use for Watershed
To
accomplish the goals of the North Lawrence Drainage Study, the ultimate land
use condition had to be determined for the study area. The future land
uses within the watershed will help determine where to focus the stormwater
system improvements and provide better insight into heading off potential
development problems. The project team conferred with the Public Works
Department, the Planning Office, and the Utilities Department of
Lawrence. Information was gathered with regard to current zoning,
potential developments and long-range plans and was used to produce an ultimate
watershed land use guide.
While the information gathered was used to create the Ultimate Build-Out map,
it was not intended to dictate specific policies with regard to land use in the
North Lawrence Drainage Area. However, certain policies could be inferred
from the findings of this study. For instance, lot splits currently
require a hydraulic study to determine impacts. Due to the extensive
hydraulic studies detailed in this report, it would not be necessary for
developers to conduct individual studies, as long as
the general recommendations of this study are followed (i.e. conveyance needs
to be maintained within the floodplain).
VI. Data Collection
Several
field visits were made to the study area to observe drainage patterns, take
photographs and verify structure sizes and orientations. A significant
portion of the North Lawrence watershed was surveyed for this project.
This information was used in the development of computer models of the
watershed. Information from the field survey forms was entered into
GIS. The basis for the evaluation of the North Lawrence watershed is the
digital base maps developed by the City. These maps also show land features with a 2-foot contour
interval. The base maps include topographical drainage information such
as open channels, bridges, culverts, manholes, inlets, and enclosed drainage
systems. They also include houses, transportation and above ground
utility locations. Field surveys were completed as part of this study to
update and verify any existing information on size, location, and slope of the
conveyance structures. Survey data on the conveyance system and watershed
characteristics were combined with the City database to create a comprehensive database of the most up-to-date
information.
VII. Internal Drainage System Analysis
The
system of City operated ditches, pipes, and pumps throughout
North Lawrence are collectively referred to as the “internal drainage system”
in this report. This system collects the drainage from about 1.8 square
miles and largely conveys it through gravity and pressure pipe to the Kansas
River. The intent of the internal drainage system analysis portion of the
North Lawrence Drainage Study was to investigate necessary improvements to the
existing infrastructure system for a 10-year frequency event, assuming the land
uses specified by the Buildout Scenario Map.
The performance of the Maple Street Pump Station (529 Maple Street) and the 2nd
Street Pump Station (732 N. 2nd Street) were closely considered in
the overall evaluation.
Results
of the hydrologic and hydraulic analyses for the set of 12 systems representing
the existing stormwater infrastructure within North Lawrence identified many
surcharge locations for the ultimate buildout
condition.
Recommendations
were determined for each conduit or channel in a system based on the analysis
of the entire system. It should be noted that improvements are to
generally be made in a downstream to upstream manner within the system, as
there is no advantage trying to deliver more flow to a downstream component
that cannot convey the existing flow. Overall costs for each system
upgrade were estimated; however, for the purposes of prioritizing public improvements
on a smaller scale, excess peak flow was determined for each main stem and each
lateral draining to the main stem of the system.
VIII. Watershed
Analysis
There
were three main goals for this portion of the study: to reduce the demand
on the 2nd Street Pump Station, to expel floodwater from the basin
during times of high water on the Kansas River, and to investigate the effects
of development in the floodplain. It is recommended that the drainage
from the area north of 24/40 Highway be cut off and the water pumped over the
levee. The recommendation for reducing the burden on the 2nd Street Pump Station appraises the 10-year event in
conjunction with the design criteria of the internal drainage system, however the 100-year event is investigated as well.
The
recommendation for future development in the watershed is to maintain the
current conveyance levels in the 100-year floodplain. This will mean
allowing no development in these areas that would reduce the capacity for
floodplain storage, and may require the purchase of small parcels of land to
set aside exclusively for ponding.
As
the area develops, it will become necessary to provide emergency services to
the homes and businesses that populate the area. This will require the
improvement of the major roads in the area and significant improvement of the
hydraulic structures which carry flow under the roads. With a more dense
urban population, the roads should be raised to meet the current APWA criteria
with regard to overtopping during the 100-year event. This will result in
some significant increases in required flow capacity over the existing
hydraulic structures.
IX. Kansas River Floodplain Analysis
The existing conditions FEMA hydraulic model was revised to assess the amount
of flooding that would occur in the North Lawrence area in the event of a
breach of the Kansas River levee system. A “most likely” breach location
was determined for the purpose of this analysis. For the levee
breech condition, a 100-year Kansas River event would result in flood levels 0
to 7 feet deep in the North Lawrence Watershed (refer to the exhibit titled
Watershed Analysis – Kansas River Inundation in Section VII).
Section I: Introduction
The
City of Lawrence has embarked on a program to develop
a stormwater management plan for the North Lawrence watershed. This
program is based on a recognized need to upgrade existing facilities to modern
design standards and to provide coordinated facilities in developing areas.
The economic well being of the City depends on its ability to attract and retain business and industry,
as well as residents to live in the City. Part of the City’s ability
to attract businesses and residents depends on its ability to provide adequate
services such as drinking water, sewers, transportation and stormwater
management. With the ever expanding urban area and associated increases
in impervious surfaces such as parking lots, the frequency with which drainage
issues occur appears to be increasing. This has caused the City to focus its attention on the need to provide adequate stormwater
management policies and infrastructure in all areas within the watershed.
The North Lawrence Drainage Study is one important step in this process.
C.
Watershed Description
The
North Lawrence watershed is estimated to be 9,100 acres generally bordered by
the Kansas River levee on the west and south and the Mud Creek levee on the east. Most of the drainage contributes to the
Maple Grove system, which either conveys water south to the City or east eventually to Mud Creek. A few areas near the levee, to the northwest and southeast,
drain directly to the Kansas River, while a thin strip of land along part of
the northeastern portion of the watershed flows directly to Mud Creek. Refer to the included North Lawrence Watershed map for an
overview of the project area.
The
Kansas River floodplain completely encompasses North Lawrence. The
natural silt loam soils are highly permeable. However, increased development
is replacing those soils with nearly impermeable clay material in certain
areas. Extremely mild slopes across the landform cause frequent ponding and roadway overtopping. Historically, North
Lawrence has been an agricultural community with low density residential
development. Pockets of commercial and industrial development now appear
in areas of the watershed. While parts of North Lawrence will likely
remain agricultural, the projected future land use in other areas will add more
and more impervious surfaces.
D. Purpose
The
Lawrence-Douglas County Planning Commission proposed this study to address repeated concerns from
residents of the North Lawrence area. Flooding problems occur in a number
of areas within the North Lawrence watershed. The major causes are as
follows:
- Development that has significantly increased
runoff from design storm events
- Undersized drainage system components such as
culverts, drainage channels, underground pipe systems and inlets
- Siltation within the storm drainage system
- Past development of flood-prone areas
- A shallow, flat and interrupted watershed
drainage network
Public comments relating to
current drainage issues, proposed developments, long-range plans, and
floodplain regulations are at the root of this study. The purpose of this
study is to identify areas with flooding problems, analyze the major elements
of the storm drainage system with respect to long-term land use, and recommend
needed improvements to correct or prevent systems from flooding. By doing
this, proposed developments and long-range plans will be influenced. At
the same time, regulations can be conceptualized to avoid potential pitfalls.
E. Scope
of Project
The
North Lawrence Drainage Study has several major components. They all
worked toward producing requirements of the system of stormwater conveyance and
infrastructure in an ultimate build-out scenario. The first step in doing
this was obtaining accurate, reliable data about the watershed. This
included past and current drainage issues and technical information on the
conveyance systems themselves. Next, there had to be an understanding of
what the build-out scenario will be and how to appropriately apply it to the
analyses. Three distinct analyses were then performed to produce
recommendations for alleviating potential problems within the watershed.
The following major tasks were included in the study:
- Integration of a public involvement program that
gathered and used information from residents, business owners, and
property owners when considering alternatives or upgrades within the
watershed
- Estimation of the ultimate land use for the
watershed
- Surveying and general inspection of the drainage
system
- Development of a digital database that shows the
existing components of the City’s
drainage system
- Evaluation of the internal drainage system for
the ultimate build-out scenario and recommendation of improvements
- Evaluation of the watershed drainage system for
the ultimate build-out scenario and recommendation of improvements
- Completion of an analysis of Kansas River flooding resulting from levee overtopping
Recommended improvements
help to determine the magnitude of the costs required to implement the needed
stormwater system upgrade. It should be noted, though, that detailed
design beyond the master planning level is required to accurately produce cost
estimates for system components.
Link to
diagram: North Lawrence Watershed
Section II: Public Involvement
The
North Lawrence Drainage Study public involvement program was designed to
establish meaningful and useful dialogue between area stakeholders, businesses
and residents in the area and the study team. A series of outreach
efforts were conducted; summaries of those efforts follow.
A. Key Stakeholder Interviews:
During
May and June, 2004, members of the team conducted stakeholder interviews to
evaluate community leaders’ perceptions and opinions about the area, drainage
needs and stormwater management in North Lawrence.
One-on-one interviews were conducted between consultant public involvement
staff and Steve Glass of the Douglas County Kaw Drainage District, Keith Browning
with Douglas County Public Works, and Ted Boyle of the North
Lawrence Improvement Association.
The
interview questions and responses are detailed below. Key themes included
the need to efficiently address the problem in terms of infrastructure needs
and costs, and to balance future development with current land use patterns.
What are your biggest
concerns/problems related to stormwater management in North Lawrence?
- Area is notorious for flooding
- Better than it used to be; impression that work
has already been done
- Pump station seems to help
- Disposal of stormwater – getting it to the river
- Dealing with areas not served by the pump
station
- Getting the water into the river
- Several low-lying areas are frequently under
water, including Lyons Park, 6th & Maple, and along Lyon
What do you see as the
biggest challenge to improving stormwater management in North Lawrence?
- Topography
- Levee
- Money
- Area between river and tracks is higher than
area north of tracks; difficult to move water from north of tracks to
river
What types of stormwater management
changes or improvements do you think would best serve the area?
· Stormwater removal is main concern
· Because of industry and planned
development, stormwater treatment may be necessary
· Deal with future development – allows
development, but does not make drainage worse
· Concerned about possible
overly-strict land use regulations which would limit development
· Development requirements that allow percolation
of water into the soil (ditches, retention basins, etc.)
· Suction pressure feed pumps to move
water out of the retention ponds, regardless of river height
· Three or four locations (including
areas where water already collects) for water retention systems, then grates
and suction/pumps to move water from those places to the river
Some
communities are now using “green” solutions such as wetlands and riparian
setback buffers to reduce the rate of stormwater run off. Do you think a
“green” solution is better for North Lawrence than “built” solutions?
·
Problems with retention because of local
concerns about mosquitoes, etc.
·
Setbacks are a good idea
·
Allowing water to re-infiltrate would be
excellent
·
Concerns if water stands for a significant amount of
time
·
Already required to some degree (setbacks)
·
Probably ideal, given topography - question is to what degree
·
Likes idea of combining retention areas with recreation
facilities – perhaps creation of a permanent lake/pond in combination with
water retention
·
Lyon Park an ideal location for drainage/retention – water goes
there anyway
·
Do not want water to stand too long – mosquitoes, West Nile virus, etc.
Do
you think North
Lawrence should be
more or less developed? What do you think it will look like in 20 years?
·
Along highway – industrial/commercial development
·
Residential – North Lawrence could help fix the lack of affordable housing
·
Needs to be more development
·
Development rules should be appropriate
for area, especially related to affordable/low-income housing
·
Lawrence should not be only for upper-class housing,
etc. Must accommodate affordable housing
·
More development to the north of town and
turnpike; residential between river and turnpike
·
Rezone for bigger lots (1/4 acre); make
sure development patterns do not increase drainage problems or cause increased
flooding/problems for neighbors
·
Avoid use of clay soils, which do not
allow infiltration, as fill
·
Currently 78% owner-occupied; nice place to live and want to
keep it that way
Should
land use planning address management of stormwater runoff? If so, how?
- Definitely
- Need new development, but must also deal with
impervious areas
- Use modern stormwater management techniques,
like infiltration
- This study should reduce need for individual
water management studies, at least in a general sense
- New flood standards already impose some
requirements throughout community
- Looking to this study for guidelines for
development
- Absolutely
- Not against development, but it must be planned
and cannot jeopardize existing homes and businesses
- Long-term solution has to manage water north of
the turnpike
- Codes must address stormwater management, but not
be so restrictive as to hurt future development
What should new streets
in North Lawrence look like?
- Need curbs; hard to get ditches to work
correctly because of flat topography
- Open ditch is at least part of the solution
- Sandy soil makes installation of curb and pipe more
costly and difficult; flat topography – hard to get water to flow; even
main drainage ditch is essentially flat
- Existing streets are too narrow for curb &
gutters
- Ditches are good because they allow
infiltration/percolation, but not large ditches like those that have been
built in some areas because they hard to mow and maintain
- Curb and gutters create concrete rivers; there is
no place for the water to go
Do you or your
constituents have additional concerns that we should know about?
·
Need to get the public involved; need to
hear their concerns
·
Do not be too restrictive on future development
·
Do not harm value of land – older residents are counting
on ability to sell land
·
Some of the new developments/housing have created problems
for long-term residents in terms of additional run-off – fallout is that there
is contention between neighbors; developers need to be held accountable
·
Study needs to present workable,
realistic solutions to drainage problems
Who
else do we need to make sure to include in the process?
·
Douglas County
Kaw Drainage District
·
Elected officials
·
Planning Commission
·
Developers
How
do most people in your community get their news/information?
·
Lawrence Journal World
·
TV 6
·
Post notice at Depot; Johnny’s Bar
B. Area Business and Resident Survey
On
June
15, 2004, 1,384 surveys were
mailed to residences and businesses in the North Lawrence area. Ninety-eight surveys were returned
either at the public drop-in center, held on June 30th, or by return
mail by the deadline of July 8, 2004.
The majority of the responses
reflected property-specific concerns and problems. Standing water in the
area and associated concerns about mosquito control were among the most common
problems noted. Recurring concerns related specifically to development
patterns, current stormwater management practices and future construction
impacts, as well as a desire to limit new development. With those
comments came concerns about enforcement of stormwater management controls with
new development and construction. The concerns were both in terms of
fears of too great of restrictions and desires for stringent development
controls.
Survey questions and
responses:
How often in the past 10
years have you had a problem with stormwater on your property?
[ 32 ] – 0 times
Address
|
Frequency
|
1567 Hwy 40
|
Yes
|
1728 E. 1500 Road
|
Twice really bad, but
every time with a heavy rain
|
1804 E. 1600 Road
|
15
|
1480 N. 1700 Road
|
Too many to count
|
1662 N. 1700 Road
|
3 or 4
|
792 N. 2nd
|
Several
|
645 N. 3rd
|
Frequently
|
1001 N. 3rd
|
1993 & 1997
|
624 N. 5th
|
1
|
725 N. 5th
|
8
|
649 N. 6th
|
Every time it rains
|
625 N. 7th
|
Every time it rains
|
227 N. 8th
|
1
|
625 N. 8th
|
2-3 times over the last
two years
|
769 Ash
|
5
|
600 Center
|
When it rains
|
310 Elm
|
20
|
411 Elm
|
Every time it rains
|
761 Grant
|
When it rains more than 1
day
|
711 Maple
|
2
|
819 Maple
|
Every time it rains
|
321
Maiden Lane
|
2
|
403 Lincoln
|
4
|
624 Lincoln
|
During heavy rains
|
641 Lincoln
|
Continual erosion; habitual standing water
|
628 Locust
|
Ongoing
|
788 Locust
|
Every time it rains
|
806 Locust
|
Continuous
|
818 Locust
|
Yearly
|
836 Locust
|
10
|
520 Lyon
|
2
|
835 Lyon
|
20
|
711
North Street
|
Often
|
732
North Street
|
Every time it rains
|
501 Perry
|
Every 1" or more
|
517 Perry
|
2
|
304 Pleasant
|
Too many to count
|
786 Walnut
|
Every time it rains
|
What types of problems
have you had?
Never
Sometimes Often
Erosion
[ 37
]
[ 20
]
[ 5 ]
Home or business
flooded
[ 45
]
[ 10
]
[ 4 ]
Over flowing
ditches/culverts
[ 22
]
[ 23
]
[ 26 ]
Standing water
outside
[ 22
]
[ 28
]
[ 30 ]
Street or driveway access
flooded
[ 32
]
[ 24
]
[ 21 ]
Other:
- 1480 N. 1700 Road – pasture flooded/electric
fences out of service
- 1567 Hwy 40 – Farm fields due to inadequate
landscaping and car accidents in Hwy 24/40 due to flooding
- 1662 N. 1700 Road – Water runs across road into
our field
- 1735 E. 1500 Road – Front ditch plugged
- 411 Elm Street – Alley always floods
- 625 Lake Street – Up the street the water stands
- 628 Locust – Curb water does not flow off, drainage easement
not graded properly
- 800 Walnut – Water does not pass through culvert
under drive
- 818 Locust – Storm runoff from several nearby
properties, mainly from the east of our property
- 827 Maple – some ditches do not drain
- Ditches and culvert need to be cleaned
- Fields with standing water
- I have noticed the (train) underpass flooded on 2nd Street
- Mainly standing water in culverts
- Mosquitoes
- Mosquitoes due to standing water (health hazard)
- Mosquitoes heavy/standing water
- No curbs on streets
- Problem corrected with cleaning ditches and
culverts
- Water backing up in basement
- Water crosses road and erodes ditches that we
mow; I’ve seen 6” – 8” of water pooled at Roanoke and 7th Street.
What do you see as major
storm water problems in your area? (Check all that apply)
[ 61 ] Poor drainage
[ 37 ] Excessive run-off from streets
[ 35 ] Loss of property values
[ 31 ] Flooding
[ 13 ] Trash removal/odors
[ 12 ] Loss of property through erosion
[ 8
] Poor water quality
[ 7
] Loss of natural habitat
[ 4
] Unsafe stream/stream bank conditions
Other:
- 1662 N. 1700 Road – Road contour to keep water
from running into our field
- 1804 E. 1600 Road – Runoff from airport
- 800 Walnut – Redo the ditch created in my yard,
which was not done properly anyway; also do something about the
property across the street
- Drainage driveway tubes block or no tube at all
- Hazard of flooding at 1732 & 1500 E. Road
- Inadequate ditches along major highway 24-40
- Install curb and gutter on some streets
- Lack of curb and gutters
- Loss of use of pasture
- Main concern is river flooding and levy breaks
- Mosquitoes!
- Mosquitoes from improper drainage in easement
- Need storm drain
- No drainage
- No stormwater system
- No well planned stormwater control at all – we
are fortunate at least to have sandy soil to absorb the water
- Poor alley upkeep holds water all the time when
it rains
- Standing water
- Uncared for property
What types of stormwater
management tools do you think would best correct the problem? (Check all that apply)
[ 48 ] Stormwater inlet and pipe systems
[ 45 ] Limit new construction that does not absorb
stormwater (impervious surfaces)
[ 30 ] Enhanced natural waterways
[ 23 ] Pump stations
[ 18 ] Open channel drainage systems
[ 15 ] Stormwater retention lakes/lagoons
Other
- All runoff from impervious surfaces should be
retained onsite
- Appropriate ditches along highway 24-40
- Better code enforcement by city, proper grading
of drainage easement
- Cisterns to reuse roof run off for grey water –
i.e., lawns & toilets. Water is too precious to waste!
- Curbs on streets
- Curbs, gutters, storm drains, wider streets
- Drop us from the floodplain
- Find out why ditch west of 1500 east will not
carry water when we have heavy rains; east ditch is fine
- Keep equipment from collapsing storm ditches and
culverts
- Keep things maintained on a regular basis
- Make sure drainage ditches are in the proper
areas and maintained
- Maybe if the city took care of the ditches –
cleaning/fixing/maintaining etc.; sometimes you clear your ditch but the
neighbor does not and the water stays
- No stormwater retention lakes/lagoons – too many
mosquitoes already
- Pump stations – expensive to maintain – tax
increase
- Put in curbs and gutters
- Stormwater detention that is underground
- Study low points and promote natural drainage
into storm drains
Development patterns can
impact how stormwater is best managed. How do you think North Lawrence should develop? (Check all that apply)
- Cease development and new construction
- Limit on amount of impervious surfaces as
percent of pervious; enforce pervious fill regulations – a 30 degree clay
slope is not pervious in a practical sense; require use of permeable
paving such as gravel and open pavers; offer rebates to homeowners
installing such paving, whether new or replacement; also to install
cistern systems
- North Lawrence has enough homes – they need to quit building,
but I guess this will never happen
Homes
[ 51 ] Large (1/4-acre+) home lots
[ 37 ] Suburban-style single-family
[ 6 ] Apartments
and/or town homes
Other:
- Large lots to keep areas for gardening - this is
the best soil for raising food and flowers
- Limit development
- None
- None
- Residential single family homes
- Restrict residential development
- Very large ˝ acre-plus home lots
Business
[ 35 ] Light industrial
[ 32 ] Office
[ 30 ] Agricultural
[ 6 ] Heavy
industrial
Other
- Light industrial north of turnpike
- None
- None
- Small business
Retail/Restaurant
[ 47 ] Stand-alone storefronts
[ 18 ] Grocery Store
[ 12 ] Strip malls
[ 7 ] Enclosed
malls
Other
- More grocery and variety stores
- No bars
- NO MORE – current impervious areas are WAY
under-utilized.
- No retail
- None
- None of these; this mess that Clay Heine has is bound
to effect stormwater drainage - I cannot imagine the county allowing
this to be built when we already have drainage problems
- None or vertical – maintain footprint
- Pharmacy, hardware store, banking facility,
laundry
- Sit-down family restaurant besides Chinese & Mexican – suggestion – buffet
restaurant
- Strip malls – limit two
- Use Tanger Mall I-70
Business Center or tear it down!; put in a grocery
store; we’ll take a Wal-Mart Supercenter
- We have empty stores and malls - let’s use them!
Additional comments or suggestions:
Site-Specific Concerns
- 1480 N. 1700 Road – My farm lies at the first
low spot north of the pump station on Maple Grove Tributary, the
confluence of the MGTJ with the ditch that drains Clark’s pond. When pump malfunctions or is overwhelmed by runoff
from up in the hills or airport area, my pasture ends up being used
against my will as a detention pond for other people’s stormwater.
This is unacceptable. Make them detain their own storm water.
Mandate 0% runoff from any new construction anywhere in the county!
- 1502 N. 1732 Rd. - Please come by and visit with
me. We have been living here since 1958 (46 years). I’ve
personally done a lot of work to improve drainage on my property …
grading, fill dirt, waterways, etc. The biggest single problem is
drainage on Roanoke (1732 Rd) and west ditch along 1500 East
road. The east ditch will carry most every situation. The west
one overflows over the road when we have a fast heavy rain.
Something is wrong.
- 1728 E. 1500 Road - Dale Black had a pond of
some type dug on his property for fill dirt to raise the height of a
modular home installed across from my property. Since that time
there has been a severe water problem coming across N. 7th (E
1500 Road) and into my front ditch from his property. This has
caused erosion in my ditch and driveway. I also think their driveway
culverts are too small to handle the water flow. I do know I have
lived at my property for 40 years and never had this problem until the
modular home was installed. Twice water overflowed my front ditch
and came halfway across my front yard – all from the excessive run-off
from across the road at Black’s property.
- 403 Lincoln - Storms and or minor rains sits in the ditch
on two sides of my property. Terrible mosquito breeding area and
dangerous when it runs across Lincoln repeatedly. Thanks for the questionnaire,
I appreciate the concern.
- 440 Lyon - As we
live on a corner lot, we get a lot of drainage from 2 street ways – in
return, the city digs our drainage ditches deeper – thus eroding our
lawn. We would like to see pipes and tubes along these streets to
preserve our lawn and property values. As well as mosquitoes
downsized due to standing water.
- 501 Perry - We have a ditch on 2 sides of our
property and the neighbors to the east do not even have a drainage tube or
ditch, so between runoff and that, we have quite a bit of water standing
for a while after a rain.
- 520 Lyon - I built
my home in 1995. Value would be far greater if I had storm water
collection instead of ditch; water always standing in my driveway – so bad
that I am having concrete replaced in 2 weeks. I’m paying the same
taxes as anyone else in our city/community; why not give me the same
service. When I built in 1995 my home was out of the floodplain –
since November 2001, I now am paying flood insurance – fix the problem –
stormwater runoff!
- 5th & Perry - The older houses in
our area seem to suffer the worst – even moderate rains flood the yard at
NW 5th and Perry. Heavy rains flood the intersection.
- 600-700 block Lincoln floods – always standing water
- 625 N 7th - Stormwater stands in
ditch in front of my house because the tube under my driveway is higher
than the bottom of my ditch. The sides of my ditch are too steep to
mow. I wish there wasn’t a ditch in front of my house. I would
prefer to have storm sewers instead.
- 628 Locust – Neighbors and I have had problems
with a drainage easement. It is not graded properly. City has been no help. Also, the curb at
the end of my driveway is deeper than the adjoining ones causing improper
drainage. Mosquitoes are a big problem. 6th & Lyons – stagnant water standing a lot of the time.
- 700 block of N. 7th does not drain.
- 760 N. 5th - David Krouse has been notified two times about our standing
water problem.
- 761 Grant - The lot behind my property is owned
by a church. They rarely mow it - hardly ever mow the ditches
between property. Those weeds get to be 10 feet high. The east
ditch does not drain. It holds a good amount of water (mosquito
lagoon). This has been a concern for several years. All I can
suggest is that the ditch be redone and filled with a drainable base so
weeds won’t grow so bad, and maybe some other things. Please look at
it.
- 786 Walnut - When electricity is off, lift
station shuts off and water backs up into our basement. Need
alternative energy source to keep pump station working.
Also persistent bad odor in outside air due to lift station. Need to
burn off excessive sewer gases to prevent smell in area.
- 8th & Lyon – See attached picture. We have concerns about the
properties on 8th & Lyon. We have problems with the ditch shown on the picture as
well as with the lines and grades of an undeveloped lot on the other side
of the street. I’m a Kansas licensed geotechnical engineer. You may
contact me at (913) 458-3955 for additional questions or comments.
- 800 Walnut – Rainwater did not stand on my
property prior to improvements made a few years ago. The culvert
pipe under my driveway was dug up, then put back
in place. Unfortunately, it was not done carefully and water doesn’t
flow through it well as it is too high now. Also the ditch created
by the city has a depression right by the entry to the east of the pipe
that allows water to pool. When they dug up my front yard to make
the ditch (which really was not needed on my side of the street) it was
done by eye. No on used any plum line or other visual aid to see if
water would flow toward the inlet pipe; they just eyeballed it. The
resulting ditch has walls that are uneven and very difficult to mow.
They did not plant grass on my property, although they did re-seed and
cover my neighbor’s property to the north, across the street.
Finally there was a second culvert/driveway to the east of my
driveway. It belonged to my neighbor according to him, but
technically about 1.5 feet of it was on my property. He talked the
workers into moving it a few yards to the east. Water does not flow
well between these two culverts now, and standing water develops
during/after steady rain. There needs to be a better drainage system
across the street. My yard needs to be either re-done so it is both mowable (easily) and drains well, or redone so that
water flows toward the inlet better. The area east of my drive needs
to be redone (with small depression filled) and perhaps the culvert pipe
replaced or moved (although filling in the depression should do).
Over the years, I have tried to dig here and there to promote flow.
This is a small problem, but since I had no problem before it is important
to me. Also I contacted the city about this years
ago; to no avail.
- 9th and Locust; fix culverts and
clean ditches; anything would help.
Capital Improvements/Maintenance
- First impressions for those traveling into Lawrence are not very good since they must drive on poor
main roads in North
Lawrence and poorly
kept used car lots. It is a shame that the “squeaky wheel gets the
grease” and a high percentage of the community money goes west of Iowa. I am pleased to see this survey and hope
the study is not just a political ploy to calm emotions.
- I suggest paving the streets, eliminating the
deep ditches, install storm sewers, clean frequently, Wow! North Lawrence!
- I would like to have ditches replaced with
stormwater drain system so ditches would be gone and have ground level and
put sidewalks along streets at least on 1 side. A lot of people like
to walk dogs and exercise and street (7th) is very narrow and
dangerous. Thanks for your help!
- I would love to see the ditches removed and
replaced with drainage systems. Most ditches in North Lawrence retain water after it rains and do not drain
properly if they drain at all. The ditches are very difficult to
maintain and the new ditches at the new elevated properties seem to be
impossible to mow.
- My property is elevated high enough that I don’t
have a problem with it. However, the property to the rear with a
field floods more and more now that many inbound lots are built on. North Lawrence needs a storm drain system badly. Insects
are very bad due to standing water. The wrecker businesses on Maple
have made it worse yet due to dead cars and semi-paved areas.
- Need curbs
- North Lawrence has been neglected long enough. We need
many improvements. Water drainage would be a good place to start,
then street improvement. Next, property improvement and an
invitation to businesses.
- North Lawrence maintenance seems to always lag behind compared
to other parts of the city. The concern and dedication to keep up by
those responsible just doesn’t seem to be there (maintenance department,
etc.) Perhaps consistent and regular attention and evaluation could
help solve some of the problems.
- Stop bringing clay for fill. Our ditches
don’t need to be dug out any deeper. The ones that have been dug out
deeper are not getting mowed.
- The alleys in North Lawrence are poorly maintained – when they finally do a
storm will come and they are right back to the same condition as before –
full of holes and full of water
- We would like to see more curb and gutters instead
of ditches. The height requirements for new lots seem too high,
especially when a new lot is built up next to an established
residence. Great improvements have been made since 1993.
- Would like for sewer lines and stormwater lines
to be separated.
Development &
Planning
- City of Lawrence needs to address allowances for permeable
paving in development guidelines. City should not ever allow new development
that forces existing homes to buy flood insurance (i.e., development
around 7th and Lake – they are taking property value from
long time residents and it is criminal).
- City requires businesses to retain their runoff.
I think the city should retain the runoff from the airport.
- Elevated buildings should be removed and
returned to the condition they were in previously. Building those
homes up like that was a slap in the face of North Lawrence residents. The water shed from those
properties must be absorbed by the rest of us.
- Grade new construction so water does not pool on
existing undeveloped property on floodplain. New pump station has
improved water management. Cudos!
- I think all deep ditches where new homes are
built should have enclosed drainage under driveways connecting – example
700 block of Lake Street, south side.
- Large lots for housing – to keep this excellent
soil for gardens. Large developments need excellent engineering so
large impermeable surfaces do not overwhelm storm drainage systems.
Natural drainage areas – grassy – contoured for mowing work well most of
the time because our soils allow water to move through them quickly.
- Let North Lawrence
develop like we do other areas. Address the drainage issues and take
into account the airport, I-70, 24 hwy, 59 Hwy – let’s be smart, do things
in a way that showcase our city and make it stand out compared to other
I-70 cities.
- Mr. Chaney is allowed to build shoddy houses on landfilled lots that erode into ditches and cause
foundation and drainage problems, not to mention yards full of weeds
because the ditches are so steep they cannot be tended. This type of
careless building also leads to standing water and out of control problems
associated with stagnant water.
- My property is located in the highest part of NL
so I have had no water problems. Most of the problems are on the
north side of the tracks (the lowest part in NL). New home
development has really grown (especially in the lower part) on every
vacant lot available – elevating these buildings has only increased the
runoff on older existing homes.
- North Lawrence is in a floodplain. No amount of
conferencing can change that. It is no exaggeration to say that it
is also some of the richest land in the world. Common sense should dictate that it be dedicated
to green space/farming. The latter should focus on appropriate
tech/organics due to proximity of residential; a diversified product with
eager local and regional markets.
- Our incredibly rich, well draining native soil
is some of the best agricultural soil in the world. We should
treasure it for its best use – food for people – and not pave or build on
it.
- People like to live in North Lawrence because it is convenient to the downtown area
for work or shopping.
- Preserve green space to allow absorption of
runoff. Larger lots, less concrete (drives, patios, etc).
Better management of ditches. Ours is so uneven in the bottom, water
is always in it making it hard to keep weeds cut. When ditches are
cleaned out, adjacent property owners should be allowed to have some of
the soil back on their property.
- Storm water poses a major impediment to
redevelopment of North
Lawrence. Most North Lawrence sandrats want a
grocery store in North
Lawrence, yet grocery
stores won’t consider North
Lawrence because there
aren’t enough roof tops to justify. Yet North Lawrence sandrats (many) want
no more development. You can’t have it both ways.
- Take a drive around North Lawrence after a heavy rain and you’ll see the
problems. Save money and get the job done. No more surveys.
- The mosquitoes are terrible due to the standing
water in the ditches of the 700 block of Lake Street because of the new houses built. This is
a health risk.
- The street side open ditch drainage system for
the 700 block of Elm Street appears to work fine, so long as the ditches
are kept clear of leaves, grass and other debris, except in times of
exceptionally extensive rainfall. Some minor problems arise when
some of those responsible for maintaining their portion of the ditch and
driveway pipes fail to do so. The only potential for improvement would
appear to be an underground storm sewer system with additional gradient,
which is apparently not practical without an extensive and expensive
pumping system to elevate the outflow above the applicable river
level. A proposal for the funding for installation of such a system
would very likely meet with strong opposition. I think that any kind
of additional development which does not engender widespread opposition on
a case by case basis, would be allowed and that correction of any drainage
problems created by such development should be funded by the developers
with such help as can be obtained by governmental agencies. The
predominance of sandy soil in this area allows extensive penetration and
reduced runoff, except in periods of exceptionally long and heavy rains.
- The town homes would be great for retired or
single females, males who really can’t tackle lawn work or repairs.
Miscellaneous
- I have not had any problems with stormwater so I
would not like to see any policies or procedures that would cost me in
either taxes or fees, or loss of property value through increased
regulation.
- I would like my property at 2nd and
Locust re-zoned so I can build a salon there.
- My home hasn’t flooded since the 1951 flood.
- Present builders keep their property mowed and
cleaned (example 4th & Lyons). Rental properties should be taken care
of and alleys should be taken care of also.
- Smell from water treatment plant!
- When will I get rural water?
C.
Public Drop-in Center:
On
June
30, 2004, a public drop-in
center was organized to collect completed questionnaires and discuss
input/concerns directly with residents and businesses in the area. In
addition to returning questionnaires, meeting participants provided the study
team with additional information on specific concerns, including digital
photography of problem areas. Thirty-three members of the public visited
the drop-in center, which was open from 11 a.m. to 6
p.m. at the Union Pacific
Depot at 2nd and Locust in Lawrence, Kansas.
The
meeting was publicized through the mailed survey and through a press release to
local media. There was also a notice on the North Lawrence Improvement
Area Website.
Exhibits
included information on various stormwater management tools, an overview of
plans and development for North
Lawrence, and a large
aerial photograph of the area. Over the course of the afternoon, in
addition to the information provided in the surveys, the public provided
the following information, concerns and questions to the study team.
- 616 Locust – City check on weather shed is within utility
easement.
- 628 Locust – Problem with water ponding on south road ditch (neighbor at 624 has had
water problems). Development problem? City has assisted developer to fix ditch; stopped
issuing permits, but no positive improvement has resulted. Concerned with mosquitoes and health. Also,
water ponds along C & G where it has to evaporate. No
water has impacted house.
- 904 N 7th – Standing water in
backyard; also, poor drainage in front yard. Ditch is very
shallow. Ends of pipe are crushed - would like it repaired.
Sump in backyard does not drain; concerns with mosquitoes. Ponds a
couple of days after rains. Also concerned with house to the north,
which is unoccupied and rarely maintained.
- 5th & Levee – Pipe drains under
levee, but roadway ditch (with minimal area) is generally dry (not really
a problem)
- Likes idea of ponds with pipes and pumps at
central locations, such as adjacent to Lyons Park, Lincoln, Third, Pleasant from 5th to 7th.
Developer filled property south of park with red clay but has not built on
it - “solved” local ponding problem. Also
concerned with very narrow width of Lake Street west of 8th Street.
- Oak between 8th & 9th:
Drainage problem has been fixed with removal of old structure
- Planned clean-out of ditch and culverts on
Walnut
- 300 block of Funston already cleaned – money
acquired by NLIA; maintenance of culverts, ditches and pipes are an
ongoing concern, including culverts at 2nd Street intersection, which are filled with sand and
not maintained
- 701 Maple – City-built pipe under 7th & a driveway -
water in warehouse twice recently
- 513 Lincoln – 8 year resident, no serious
flooding issues. Noted that 2nd Street railroad underpass is vulnerable to clogging.
- 818 Locust – culverts along locust, ponds on
property
- 308 N. 8th – 1993 sink hole at 2nd
and Locust.
- 422 Locust, next to Tropicana. Locust
floods; basement floods although not much in past couple of years since
the Tropicana parking lot was built. Low place in yard collects
Locust run-off after heavy rainfall and ponds – stays flooded for one day
or so.
- 7th & Lyon is deepest street ponding problem area; ponding also at 6th & Lyon.
- 3rd & Perry – NW corner – water
in basement through rock wall. Started after city sanitary sewer
work that penetrated clay layers.
- 3rd & Lyon – sewage back-ups with heavy rains.
- 820 Oak – Recent Monday evening rain, standing
water on most streets, including bridge.
- Did not like survey or meeting time; pit
problems adds to street
D. Lawrence Planning Commission Update:
Members
of the project team provided an overview of study activities and public input
to the Lawrence Planning Commission on October 13, 2004. That overview included information about the
study goals, process and timeline, as well as a review of survey results.
Section III: Ultimate Land Use for Watershed
To
accomplish the goals of the North Lawrence Drainage Study, the ultimate land
use condition had to be determined for the study area. The future land
uses within the watershed will help determine where to focus the stormwater
system improvements and provide better insight into heading off potential
problems with development. The project team conferred with the Public
Works Department, the Planning Office, and the Utilities Department of
Lawrence. Information was gathered with regard to current zoning,
potential developments, and long-range plans.
A. Key Land Use Assumptions
The
study team was tasked with developing possible future land uses for the North Lawrence study area at full build-out. There are
numerous definitions for what true build-out of an area entails. For the
purposes of this study, the definition of build-out was the probable, ultimate
development within the study area that can be reasonably accommodated within existing environmental constraints and likely
urban service area expansions, including roads, utilities (sewer and water) and
City services. It is not assumed that the entire
study area will ultimately urbanize. There are areas that are likely to
remain “rural” or in agricultural use. These areas are noted as
“Agricultural” on the Build-Out Scenario Map at the end of this section.
A
second key assumption deals with the purpose of the ultimate future land use
map. The study utilized Horizon 2020 as a resource for the creation of
the Build-Out Scenario Map. However, it should be noted that Horizon 2020
is the guiding policy document which defines a land use vision for the next
twenty years. This drainage study was tasked with developing a plan for
ultimate build-out which will reflect possible land uses beyond a twenty year
horizon. For this reason, possible future land uses were identified
outside of the Horizon 2020 Plan area to reflect ultimate growth within the
study area. As a rule, Horizon 2020 land use delineations and definitions
were used in the final scenario map. The Build-Out Scenario Map was
developed for the drainage study for the purpose of determining the impact of
an ultimate development scenario. It is not a policy document and may not
reflect best planning practices. The Lawrence City Commission and Planning Commissions may change priorities over time, impacting future land use.
Therefore, delineations shown on the Build-Out Scenario Map were based on
a combination of existing land use policies and recent development trends.
B. City Input
Understanding
the importance of input and concurrence from City staff and stakeholders, the Build-Out Scenario Map was reviewed by
various City departments prior to using the information in
watershed modeling. The following is a list of responses to comments
received on January 31, 2005 concerning the drainage study’s future land use map.
The project team made appropriate modifications to the map based upon the
review comments. The bulleted list provides the City’s questions/comments (Q/C) followed by the drainage study team’s answer/modifications and/or
clarifications (A):
Q/C: Have
you asked Parks and Recreation for any long-term plans? The open space
would need to reflect corridors, paths, etc. They will not want to
inherit random tracts to maintain.
A: The Parks and Recreation
Department was contacted to inquire about a long-term plan for parks, open
space, and trails. Parks and Recreation are currently in the process of
developing a plan and standards for developing areas. However, to date,
no plans have been delineated for the project study area beyond Horizon 2020.
The Build-Out Scenario Map was amended to show floodplain and open space
areas as well as riparian corridors for possible green space connections.
As previously mentioned, the goal of this effort is not to develop a policy
map. Rather, the intention is to delineate how the study area will likely
develop at build-out.
Q/C: A
lot of the low density areas are very low-lying. Should we
have another symbol for low density that would require several (6+) feet of
fill relative to current FEMA? These could be argued as permanent
agricultural.
A: The Build-Out Scenario Map
was changed to reflect the 100-year floodplain areas for the study area.
Best practices advocate that these areas be delineated as permanent
agricultural or at least Very Low Density Residential. However, there are
few tools available to FEMA, the City and Counties to actively enforce such policies. Developers may fill
floodplain areas or raise structures above base flood elevations per FEMA
standards. The floodplain and low lying areas on the Build-Out Scenario
Map were amended to either Parks & Open Space or Agricultural.
Q/C: How
closely was Horizon 2020 followed? It seems that prevailing development
activity is moving to commercial/industrial along the highways.
A: As mentioned previously,
we amended the Build-Out Scenario Map to reflect the Horizon 2020 as closely as
possible. For the purposes of this study, some land use delineations were
combined (there are several categories of industrial and office) to simplify
designations. Additionally, some of the low-lying areas were designated
Agricultural. It is assumed that an average density within these areas is
1 Dwelling Unit per 5-Acres. The balance of the designations on the
Build-Out Scenario Map is consistent with Horizon 2020.
The
industrial and commercial trends are expanding along the highways. Best
practices advocate a clustering of these uses at designated nodes with access
to infrastructure and compatible uses. This policy is reflected in
Horizon 2020. The study team amended the Build-Out Scenario Map to show
commercial areas along the Highways and intersections of major roads.
Industrial developments are shown near the Lawrence Municipal Airport.
Q/C: The KU
Endowment Association owns substantial parcels.
A: The KU Endowment
Association was contacted during the study. The Association does own a
substantial amount of property around the airport (approximately
220-acres). Currently, much of this property is farmed. However,
the Association anticipates that the property will eventually develop.
There have been discussions to develop the remaining property adjacent to the
airport into commercial and/or industrial uses.
Q/C: Contiguous green space would be desirable for linkages
and connectivity.
A: As mentioned previously,
we amended the Build-Out Scenario Map to show riparian corridors. Parks
and Recreation is in the process of developing a plan and standards for future
development areas.
Q/C: The
Low Density assumption of 3 dwelling units per acre (du/acre) varies from Horizon 2020 which defines low density
as 6 du/acre or less.
A: Future suburban
areas are unlikely to develop at the same density as areas within the
established core. The task within this drainage study requires developing
densities for areas outside of Horizon 2020. Prevailing trends show that
a majority of development in suburban areas consist primarily of single-family
detached homes with approximate densities of 3 units per acre. To reflect
these trends, the designation “Suburban Residential” is provided on the
Build-Out Scenario Map for areas outside of Horizon 2020.
Q/C: Need
to note that Very Low Density is defined in Horizon 2020 as 1 du/acre or less.
A: This is reflected in
the latest Build-Out Scenario Map.
Q/C: Need
to identify areas for continued Ag uses: either along Hwy 24/40; east of E1600 Rd; southeast part of study area. Ag uses could
be combined with the Very Low Density residential uses.
A: As mentioned previously,
the Build-Out Scenario Map was updated to show the designation of
Agricultural. The study team agrees that some areas are likely to remain
in agricultural use while other areas may develop at very low densities.
We assume that future development will follow Horizon 2020 policies that
encourage residential clustering. A probable build-out assumption for
these areas would be an average of 1 dwelling unit per 5-acres.
Q/C: The
Very Low Density residential land use at the east end of the railroad tracks
seems odd. This area might work better as an active parks area. The
area along E 1600 Rd south of Hwy 24 might also be good area for active parks
use or Ag uses.
A: The
Build-Out Scenario Map was amended to show this area as Agricultural.
Q/C: Might
be helpful to show planned bike route (N 7th [E 1500 Rd north
to County line] to N 2000 Rd to E 1600 Rd to N 1650 Rd).
A: The intended purpose of the
Build-Out Scenario Map is developing probable land uses at build-out for the
drainage model. Bike routes and other information that is usually
depicted on land use plans and development guides have not been
included.
Q/C: Horizon
2020 anticipates a new neighborhood commercial node at N 7th &
Hwy 24/40. It looks really large on map (may be the scale issue).
A: Part of this was a
scale issue. However, the commercial node on the Build-Out Scenario Map
was modified to show a modest expansion of this area reflecting growth beyond
the time horizon depicted in Horizon 2020.
Q/C: Horizon
2020 does not show any type of commercial node east of City at N 1600 Road.
A: Again, the purpose of the
Build-Out Scenario Map is to anticipate development beyond Horizon 2020.
For the purposes of this exercise, it was prudent to show realistic expansions
of commercial. However, further review led to the final version of the
map showing this particular area as agricultural.
Q/C: Map
extends into Leavenworth County. Need to accurately show Douglas County line on east side.
A: The County lines are depicted on the latest version of the Build-Out Scenario
Map.
Q/C: We
would like to see less industrial uses along Locust Street from 2nd to 8th Streets, along
Maple
Street
from 2nd to 8th Streets and along Grant Street from 7th to 9th Streets.
A: The Build-Out Scenario Map
is not a policy document; it is for study purposes only. The industrial
land use designations pointed out in the comment from the North Lawrence
Improvement Association are within the Lawrence City Limits and are shown as industrial in Horizon 2020. The
requested changes should occur only through a plan amendment of Horizon 2020.
Q/C: What
is developable open space and how would it be used?
A: Currently, the developable open space has been removed from the Build-Out
Scenario Map. This is a topic that needs to be discussed with the City because, as stated earlier, HNTB amended the Build-Out Scenario Map to
reflect the 100-year floodplain areas for the Study Area. Best practices
advocate that these areas be delineated as permanent agricultural or at least
Very Low Density Residential. However, there are few tools available to
FEMA, the City and Counties to actively enforce such policies. Developers may fill
floodplain areas or raise structures above base flood elevations per FEMA
standards. HNTB amended the floodplain and low lying areas on the
Build-Out Scenario Map as either open space or Agricultural.
C.
Mapping Results
The
final scenario map used in the hydrologic analysis of the study contained the
land use categories shown in the table. Several defined uses for
residential were used to demonstrate the likely variance in potential development.
Land Use Categories
![](N_Law_Drainage_Study_2005_files/image002.gif)
The next page is the final
Build-Out Scenario Map produced for the North Lawrence Drainage Study.
Link to
diagram: North Lawrence
Drainage Study Build-Out Scenario Map
Section IV: Data Collection
A. Field
Investigation
Several
field visits were made to observe drainage patterns, take photographs, and
verify structure sizes and orientations. A few photos of significant
features are shown below.
Ponding
downstream of 1400/1900 intersection, south of Midland
![](N_Law_Drainage_Study_2005_files/image004.jpg)
3-108” CMP under RR
tracks, west of 24/40 intersection
![](N_Law_Drainage_Study_2005_files/image005.jpg)
Tributary B, near the mouth
![](N_Law_Drainage_Study_2005_files/image006.jpg)
Lake adjacent to RR and 24 Highway, NW of Midland
B. Surveys
The
entire drainage system in the North
Lawrence watershed study
was surveyed by Landplan Engineering, P.A.
System characteristics determined in the field included the following:
Culverts and Bridges
·
Location
·
Structure type
·
Size
·
General condition
·
Flow line elevations
·
Overtopping Elevations
Inlets
·
Location
·
Grate/curb dimensions
·
Construction material
·
General condition
·
Invert information
·
Flow direction
·
Size of incoming and outgoing pipes
·
Depth and elevation of incoming and
outgoing pipes
Manholes
·
Location
·
Rim/cover/barrel elevation
·
Wall material
·
Invert type and condition
·
Depth (rim to flow line) and pipe
diameter
Open
Channel Hydraulic Data
·
Cross Sections
This
information was used in the development of computer models. Information
from the field survey forms was entered into the GIS database and mapping.
C.
GIS Mapping
The
basis for the evaluation of the North Lawrence
watershed is the digital base maps developed by the City. These maps also show land features with a 2 foot contour
interval. The base maps include topographical drainage information such
as open channels, bridges, culverts, manholes, inlets and enclosed system
drainage. They also include houses, transportation and above ground
utility locations.
The
City’s surveyed as-builts
were used to digitize the pipe location and an existing data base provided
information on the pipe network. Field surveys were completed as
part of this study to update and verify any existing information on size,
location and slope of the conveyance structures. Survey data on the
conveyance system and watershed characteristics were combined with the city
database to create a comprehensive database with the most up-to-date
information.
Two
reports reviewed, “Internal Drainage Study, North Lawrence Flood Protection
Unit” and “Lawrence, Kansas, Stormwater Management Master Plan,” also provided
insight into the drainage problems in the North Lawrence watershed.
Link to
diagram: North Lawrence Watershed
Surveys 1
North Lawrence Watershed Surveys 2
Section V: Internal Drainage System Analysis
Link to
diagram: Internal Analysis
The
system of City operated ditches, pipes, and pumps throughout North Lawrence are collectively referred to as the “internal
drainage system”. This system collects the drainage from about 1.8 square
miles and largely conveys it through gravity and pressure pipe to the Kansas River (refer to the Internal Analysis map at the beginning
of this section). The intent of the internal system analysis portion of
the North Lawrence Drainage Study was to investigate necessary improvements to
the existing infrastructure system for a 10-year frequency event assuming the
land uses specified by the Build-Out Scenario Map. The performance of the
Maple Street Pump Station (529 Maple Street) and the 2nd Street Pump Station (732 N. 2nd Street) were closely considered in the overall evaluation.
A. General
Methodology
The
drainage area contributing to stormwater system infrastructure within the City limits was divided into 64 sub-areas having an average size of about
17 acres. The smallest sub-area was about 0.5 acres, with the largest
covering about 64 acres. The modeling of the internal drainage system was
broken into 12 individual systems based upon natural topographic division and
unique outlets. Seven systems currently drain through the levee by
gravity means, two are pumped, and the remaining three drain to low-lying
areas. A combination of survey data, City GIS data, and minimal interpolated data provided the database for
the system of inlets, manholes, and pipes. Typical ditch sections were
assumed from field investigation and survey notes.
The
approach to determining appropriate improvements for the North Lawrence
Drainage Study’s internal drainage system began with several guiding
principles:
- In areas not near a pump plant, increase pipe
sizes and/or channel capacity
- At the Maple Street pump plant, investigate an increase in the
plant capacity
- Investigate the adequacy of the 2nd Street pump plant, assuming no contributing flow from
the watershed north of US 24
- Detention should be accomplished on existing
topography – avoid excavation
- If ditch sizes are increased, avoid changing the
slope
- Do not modify pipes extending through the levee
Taking
these items into consideration, the 12 individual systems were analyzed.
As each one was modeled, the determination was to be made if that system would
remain separate or potentially contribute flow to another system. The
10-year event was run for each existing network of manholes, inlets, junction
boxes, pipes, and channels to determine problem areas and provide
recommendations for those areas.
B. Findings and Recommendations
Results
of the hydrologic and hydraulic analyses for the set of 12 systems representing
the existing stormwater infrastructure within North Lawrence identified many surcharge locations for the ultimate
build-out condition. Recommendations for potential improvement followed
the guiding principles outlined above as closely as possible.
For
areas that drain by gravity flow to the river (no pump plant), various pipe and
channel configuration upgrades were tested. The shallow cover on most of
the pipes within the drainage network did not allow for keeping the same slope
in the line. Usually, to eliminate a ponding
situation, most of the system had to be redesigned. In other words,
increasing pipe and channel sizes in conjunction with changing grades was
necessary. The structure draining through the levee, however, was able to
remain in place with the recommended redesign of the upstream portion of the
system in all of these situations.
The
second case is where the system is essentially self-contained (flowing to a
low-lying area) and the analysis shows that it has areas of surcharge or ponding. The total volume of ponding
was compared to available ponding area at that
location. If adequate volume was available, then no recommended changes
were necessary. The recommendation only includes the cost of acquiring
the parcel(s) of land that is used for ponding.
If the volume available according to surveys and contour information was
inadequate, then the flow might need to be re-routed at one or more
locations. The three cases for North Lawrence had
ample ponding area available to handle the volume of
surcharge.
A
final situation involves the systems which include the Maple Street pump station and 2nd Street pump station. Investigation of potential
upgrades to the pump stations were included as part of the alternatives
analysis process, along with alterations to conduits and channels.
Significant upgrades to the pump stations in terms of pumping capacity were
determined necessary for the ultimate build-out condition. While the
original intent was to maintain the use of the existing discharge pipes from
each pump plant, it turned out that those pipes were grossly inadequate and
alternative recommendations had to be made.
Recommendations
were determined for each conduit or channel in a system based on the analysis
of the entire system. It should be noted that improvements are to
generally be made in a downstream to upstream manner within the system, as
there is no advantage trying to deliver more flow to a downstream component
that cannot convey the existing flow. Overall costs for each system
upgrade are summarized in the spreadsheets on the following pages.
However, for the purposes of prioritizing public improvements on a smaller scale,
excess peak flow was determined for each lateral draining to the main stem of
the system. A comparison of the discharge through the existing lateral at
the main stem location - that which does not surcharge and exit the lateral
somewhere along its path - and the recommended configuration provided the
excess flow values. The excess peak flows were also recorded for the most
downstream pipe or channel on the main stem of each system. The most
downstream conveyance link of a system is the only item included in
prioritization for some systems because the drainage area of the entire system
is relatively small (less than about 100 acres) and no laterals were
modeled. A priority listing encompassing the 12 system study area is
given in the table.
Prioritization of Systems
|
Link Name
|
Excess Peak Flow
|
Total Estimated Cost of Improvements
|
(cfs)
|
(dollars)
|
S1-1
|
315
|
$9,163,000
|
S6-1
|
168
|
$3,994,000
|
S9-1
|
133
|
$1,132,000
|
S1L1-1
|
96
|
$333,000
|
S1L5-1
|
85
|
$235,000
|
S1L7-1
|
85
|
$59,000
|
S1L3-1
|
56
|
$187,000
|
S6L3-1
|
56
|
$195,000
|
S6L3-7D
|
0
|
$181,000
|
S4-1
|
43
|
$60,000
|
S6L2-1
|
37
|
$5,000
|
S4L4-1
|
35
|
$53,000
|
S4L2-1
|
27
|
$36,000
|
S9L1-1
|
21
|
$7,000
|
S1L2-1
|
20
|
$240,000
|
S8-1
|
17
|
$115,000
|
S10L2-1
|
13
|
$4,000
|
S7-1
|
13
|
$38,000
|
S5-1
|
10
|
$56,000
|
S10-1
|
6
|
$106,000
|
S1L4-1
|
1
|
$7,000
|
S1L6-1
|
0
|
$0
|
S11-1
|
0
|
$0
|
S3-1
|
0
|
$0
|
S2-1
|
0
|
$0
|
S12-1
|
0
|
$0
|
Total
|
0
|
$16,206,000
|
The
costs shown in the table provide a conceptual level estimate of capital costs
to implement the recommendation for each lateral. Labor and construction costs
are included, but items such as engineering design and maintenance of those
structures are not. Unit prices for labor and construction were obtained
from the 2005 RS Means Construction Cost Manual. Land/easement acquisition costs, obtained from the Douglas County
online appraisal system (http://www.douglas-county.com/online_services/online_services.aspx), were
added to the appropriate systems as part of the total cost.
It
is important to note that specific conditions of a site can significantly
affect the cost to replace structures or implement other solutions.
Extraordinary circumstances were not taken into account for the conceptual
level costs determined by this study. Reasonable unit costs were
determined and applied to recommended improvements across the entire study
area. Also, the implementation costs for recommended improvements on the
laterals do not reflect the main stem improvements that may be necessary in
conjunction with the lateral improvements. In other words, whatever
portion of the main stem is recommended for improvement downstream of the
lateral should be implemented at the same time (or prior to) as the lateral
improvements. The cost of the lateral improvement in the listing,
however, is exclusive of that downstream cost.
The
next several pages provide details of the recommendations for the individual
systems included in the internal system analysis portion of the study. A
description is followed by a map of the system identifying each conduit,
channel, or pump plant that is recommended for improvement and its respective
cost. The two numbers below the cost figure (shown as X/Y) represent a
comparison between full-flow capacity of the existing conduit and the flow
through the recommended conduit. Additional detail for pipe and grade changes,
as well as pump plant upgrades, is shown on the spreadsheets for each
system. Costs for each lateral are broken down as subtotals to
the overall system cost.
1.
System 1
System
1 has a pressure flow outlet pipe through the levee originating from the 2nd Street pump station. Each conduit and channel, as
well as the pump plant, was analyzed with regard to capacity during a 10-year
flow event. A method of upsizing pipe and changing grade from downstream
to upstream was utilized to eliminate those that were over capacity.
There are a total of 60 conduits in this system, of which 52 are exceeding
capacity. Channels total 28, of which 26 are over
capacity. The 2nd Street pump station receives 549 cfs
in the ultimate build-out condition, assuming that the recommended flow cut-off
at US-24 is in place. The Maple Grove cut-off is discussed in detail in Section VI of this
report and should be considered with regard to the inundation area represented
on the System 1 mapping. The current pumping capacity of the 2nd Street station is 107 cfs, which
is 442 cfs deficient for the ultimate condition.
·
SlL1 – The excess peak flow in S1L1-1,
the pipe discharging to the main stem of System 1, is 96 cfs.
Almost all of the points along the lateral were shown to be surcharging.
Minimal cover and slope issues forced the entire lateral to be
redesigned. A more consistent grade was set and sizes were changed on a
segment-by-segment basis in order to eliminate surcharge points. The
process continued until each component of the lateral could handle the flow
without surcharge. Eight out of nine pipes have recommendations for size
change, while all have slope changes.
·
S1L2 – The excess peak flow in S1L2-1,
the channel discharging to the main stem of System 1, is 20 cfs.
A majority of the points along the lateral were shown to be surcharging.
Minimal cover and slope issues forced most of the lateral to be
redesigned. A more consistent grade was set and sizes were changed on a
segment-by-segment basis in order to eliminate surcharge points. By
improving one situation, problems often progressed to (or added to flooding
problems at) adjacent pipes. The process continued until each component
of the lateral could handle the flow without surcharge. All 20 pipes/channels
have recommendations for size change; while 17 have slope change
recommendations.
·
S1L3 – The excess peak flow in S1L3-1,
the channel discharging to the main stem of System 1, is 56 cfs.
All of the points along the lateral were shown to be surcharging. Minimal
cover and slope issues forced the entire lateral to be redesigned. A more
consistent grade was set and sizes were changed on a segment-by-segment basis
in order to eliminate surcharge points. The process continued until each
component of the lateral could handle the flow without surcharge. All 10
pipes/channels have recommendations for size and grade changes.
·
S1L4 – The excess peak flow in S1L4-1,
the channel discharging to the main stem of System 1, is 0 cfs.
No changes in size or slope are necessary for these pipes.
·
S1L5 – The excess peak flow in S1L5-1,
the channel discharging to the main stem of System 1, is 85 cfs.
A majority of the points along the lateral were shown to be surcharging.
Minimal cover and slope issues forced most of the lateral to be
redesigned. A more consistent grade was set and sizes were changed on a
segment-by-segment basis in order to eliminate surcharge points. By improving
one situation, problems often progressed to (or added to flooding problems at)
adjacent pipes. The process continued until each component of the lateral
could handle the flow without surcharge. All 11 pipes/channels have
recommendations for size and slope change.
·
S1L6 – The excess peak flow in S1L6-1,
the pipe discharging to the main stem of System 1, is 1 cfs.
This is the only pipe in the lateral, and a change in grade is
recommended. The size of the pipe was determined to be adequate for the
ultimate build-out condition.
·
S1L7 – The excess peak flow in S1L7-1,
the channel discharging to the main stem of System 1, is 84 cfs.
All of the points along the lateral were shown to be surcharging. Minimal
cover and slope issues forced the entire lateral to be redesigned. A more
consistent grade was set and sizes were changed on a segment-by-segment basis
in order to eliminate surcharge points. By improving one situation,
problems often progressed to (or added to flooding problems at) adjacent pipes.
The process continued until each component of the lateral could handle the flow
without surcharge. Five out of six pipes/channels have recommendations
for size change, while all have slope changes.
Link to Cost estimate: System 1
Link to
diagram: Internal Analysis, System 1
2.
System 2
This
system has a gravity flow outlet through the Kansas River levee for approximately a five acre area. Each
pipe was analyzed with regard to capacity during a 10-year flow event.
The two pipes in this system were determined to be adequate; however, it was
discovered during the study that the gate on the outlet pipe is permanently
closed. The analysis, therefore, turned to a determination of
available storage area for ponding. The volume
of flow is relatively minor and can remain on site beyond the base of the levee
as shown on the System 2 map. As no changes are recommended, the map for
System 2 does not have any callouts.
Link to Cost estimate: System 2
Link to
diagram: Internal Analysis, System 2
3.
System 3
This
system has a gravity flow outlet through the Kansas River levee for approximately a 23 acre area. Only
the outlet pipe met the study criteria of having an individual drainage area in
the hydrologic model, and therefore could be analyzed with regard to capacity
during a 10-year flow event. However, an additional small pipe and
natural channel are included in the GIS mapping for the system. The
outlet pipe was determined to be adequate and the recommendation is to keep the
existing infrastructure in place. As no changes are recommended, the map
for System 3 does not have any callouts.
Link to Cost estimate: System 3
Link to
diagram: Internal Analysis, System 3
4.
System 4
This
system has a gravity flow pipe outlet to the Kansas River. Each conduit was analyzed with regard to
capacity during a 10-year flow event. A method of upsizing pipe and
changing grade from downstream to upstream was utilized to eliminate those that
were over capacity. A total of 13 pipes met criteria for analysis in
System 4 (31 pipes are shown in GIS), of which 8 are exceeding capacity.
On the main stem, two out of seven pipes are recommended for an upgrade in size
and change in slope. The other five are determined to be adequate for the
ultimate build-out condition. A breakdown of each lateral coming into the
main system is given below. A map of this system identifies all
recommended improvements along with an estimated total cost. Additional
detail for improvements is shown on the System 4 spreadsheet.
- S4L2 – The excess peak flow in S4L2-1, the pipe
discharging to the main stem of System 4, is 27 cfs.
One of the points along the lateral was shown to be surcharging. In
order to provide an adequate conveyance system, all four of the pipes are
recommended for size increases. However, the existing grades can
accommodate the new sizes.
- S4L4 – The excess peak flow in S4L4-1, the pipe
discharging to the main stem of System 4, is 35 cfs.
Both the discharge pipe and the one other pipe along the lateral were
shown to be surcharging. In order to eliminate the ponding, size increases are recommended. As with
the other System 4 lateral, the existing grades can accommodate the new
sizes.
Link to Cost estimate: System 4
Link to diagram:
Internal Analysis, System 4
5.
System 5
This
system has a gravity flow outlet through the Kansas River levee. Each of the two pipes in this system
was analyzed with regard to capacity during a 10-year flow event. One of
the pipes, the upstream conduit, was determined to be exceeding its
capacity. An upgrade to the size of that pipe, while keeping the slope
constant, provides adequate drainage for the system. The levee pipe can
handle the additional flow delivered by the upsized pipe upstream. So, it
is recommended to keep the existing infrastructure in place at that
location. A map of this system identifies the recommended improvement
along with an estimated total cost. Additional detail is provided on the
System 5 spreadsheet.
Link to Cost estimate: System 5
Link to
diagram: Internal Analysis, System 5
6.
System 6
This
system contains the Maple Street pump station, which discharges stormwater to the south side of the
railroad tracks running south of Maple Street. It then flows by gravity down 6th Street through the levee to the Kansas River. Each conduit and channel, as well as the pump
plant, was analyzed with regard to capacity during a 10-year flow event.
It was quickly recognized that the existing pump station force main is
extremely inadequate. The station was converted from a sanitary lift
station and the discharge is only a 9” conduit. In order to pump
significant stormwater flows, the velocity through the outlet pipe would be
very high. A consistent approach of increasing pipe sizes and changing
grades from downstream to upstream was utilized to eliminate all pipes in the
system that were over capacity. It was found that 21 out of 33 pipes are
over capacity within the system, along with the one natural channel.
Following upgrades to the piping system, the Maple Street pump station would need to pump a peak of 302 cfs from its wet well.
Based
upon a specific standing water concern in the block between 7th, 8th,
Lincoln, and Lyon Streets, an alternative for Section 6 looked at re-routing
some discharge to System 10. It turned out that diversion of a portion of
flow to System 10 provided an overall cost savings. While there was
additional cost for placing a new pipe along Lyon Street from 7th to 8th Streets and
land acquisition cost to provide a drainage path to the System 10 ponding area, there was a significant reduction in the cost
of upgrading the Maple
Street pump
station. Following upgrades to the piping system, the Maple Street pump station would need to pump a peak of 238 cfs from its wet well. It was assumed that the new
diversion pipe would be placed within City right-of-way so that no additional land acquisition would be
necessary. Also, a cost for purchasing land at the ponding
area is included in System 10 already. The contribution from System 6
does not change the number of parcels slated for acquisition. The
recommendation for System 6, therefore, is to implement the flow diversion
alternative.
Even
with the flow diversion, though, local drainage would continue to cause some
standing water due to the fill currently being placed on the east side of the
lot. The City was unable to determine the ultimate location and
elevation of fill at the time of this report, but a natural drainage path to
the northeast is already being cut off. Therefore, part of the
recommendation for System 6 is to grade the local area of concern to drain to a
new 30” RCP lateral which would be connected to the new pipe
along Lyon
Street.
On
the main stem of System 6, 7 out of 16 pipes are recommended for a change in
slope, while all are recommended for an upgrade in size. A breakdown of each
lateral coming into the main system is given below. A map of this system
identifies all recommended improvements along with an estimated total
cost. Additional detail for improvements is shown on the System 6
spreadsheet.
- S6L2 – The excess peak flow in S6L2-1, the pipe
discharging to the main stem of System 6, is 37 cfs.
This is the only pipe meeting study criteria for hydrologic analysis on
that branch of the system. In order to provide an adequate
conveyance system, the pipe is recommended for a size increase and a grade
change.
- S6L3 – The excess peak flow in S6L3-1, the pipe
discharging to the main stem of System 6, is 56 cfs.
All of the points along the lateral were shown to be surcharging.
Minimal cover and slope issues forced the entire lateral to be
redesigned. A more consistent grade was set and sizes were changed
on a segment-by-segment basis in order to eliminate surcharge
points. The process continued until each component of the lateral
could handle the flow without surcharge. All 10 pipes/channels have
recommendations for size and grade changes.
Link to Cost estimate: System 6
Link to
diagram: Internal Analysis, System 6
7.
System 7
This
system has a gravity flow outlet through the Kansas River levee. Each of the two modeled pipes in this
system was analyzed with regard to capacity during a 10-year flow event.
One of the pipes, the upstream conduit, was determined to be exceeding its
capacity. An upgrade to the size of that pipe, while keeping the slope
constant, provides adequate drainage for the system. The levee pipe can
handle the additional flow delivered by the upsized pipe upstream. So, it
is recommended to keep the existing infrastructure in place at that
location. A map of this system identifies the recommended improvement
along with an estimated total cost. Additional detail is provided on the
System 7 spreadsheet.
Link to Cost estimate: System 7
Link to
diagram: Internal Analysis, System 7
8.
System 8
This
system has a gravity flow outlet through the Kansas River levee. Only the main stem components of the
system met the study criteria of having an individual analysis in the
hydrologic model, and therefore could be analyzed with regard to capacity
during a 10-year flow event. However, six additional small laterals are
included in the GIS mapping for the system. Almost all of the points
along the main line of the system were shown to be surcharging. Minimal
cover and slope issues forced the entire line to be redesigned. A more
consistent grade was set and sizes were changed on a segment-by-segment basis
in order to eliminate surcharge points. The process continued until each
component of the system could handle the flow without surcharge. Fourteen out
of 15 pipes have recommendations for size and slope changes. The outlet
pipe was determined to be adequate and the recommendation is to keep the existing
infrastructure in place. A map of this system identifies all recommended
improvements along with an estimated total cost. Additional detail for
improvements is shown on the individual system spreadsheet.
Link to Cost estimate: System 8
Link to
diagram: Internal Analysis, System 8
9.
System 9
This
system has a gravity flow outlet through the Kansas River levee. Each of the five modeled pipes in this system
was analyzed with regard to capacity during a 10-year flow event and was found
to be exceeding their capacity. An upgrade to the size of the pipes, and
a change in the slope, provides adequate drainage for the system.
The
levee pipe cannot handle the additional flow delivered by the upsized pipe
network upstream. Water will surcharge from the end of pipe S9-2 and
overland flow into the ponding area denoted in the
map. In a more populated area this would require construction of a pump
plant to take the water to the river, but at this point it runs to an
uninhabited area. Further investigation and land acquisition purchases
may be necessary prior to future development in the area. For the current
situation, though, it is recommended to keep the existing infrastructure in
place at the levee location.
A
breakdown of each lateral coming into the main system is given below. A
map of this system identifies the recommended improvements along with an
estimated total cost. Additional detail is provided on the System 9
spreadsheet.
- S9L1 – The excess peak flow in S9L1-1, the pipe
discharging to the main stem of System 9, is 21 cfs.
This is the only pipe meeting study criteria for hydrologic analysis on
that branch of the system. In order to provide an adequate
conveyance system, the pipe is recommended for a size increase and a grade
change.
Link to Cost estimate: System 9
Link to
diagram: Internal Analysis, System 9
10. System 10
This
system drains to a low-lying area on the east side of its drainage area.
Each conduit was analyzed with regard to capacity during a 10-year flow
event. A method of upsizing pipe and changing grade from downstream to
upstream was utilized to eliminate those that were over capacity. A total
of seven pipes/channels met criteria for analysis in System 10 (11 pipes are
shown in GIS), of which 5 are exceeding capacity. On the main stem, the
solitary pipe is recommended for an upgrade in size only. Of the three
channels, none are recommended for an upgrade in size, but all four have
recommended changes in slope. The ponding area
spreads across parts of three properties. It is recommended to purchase
these properties rather than convey the stormwater elsewhere.
A
breakdown of each lateral coming into the main system is given below. A
map of this system identifies all recommended improvements along with an
estimated total cost. Additional detail for improvements is shown on the
System 10 spreadsheet.
- S10L2 – The excess peak flow in S10L2-1, the
pipe discharging to the main stem of System 10, is 13 cfs.
Both the discharge pipe and the one other pipe along the lateral were
shown to be surcharging. In order to eliminate the ponding, size increases and grade changes are
recommended. The channel in between the two pipes adequately conveys
flow through the system, so it is recommended to leave that existing
infrastructure in place.
Link to Cost estimate: System 10
Link to
diagram: Internal Analysis, System 10
11. System 11
This
system flows by gravity to a low-lying area on the north end of its drainage
area. Only the outlet channel met the study criteria of having an
individual drainage area in the hydrologic model, and therefore could be
analyzed with regard to capacity during a 10-year flow event. However, an
additional six pipes and five natural channels are included in the GIS mapping
for the system. The outlet pipe was determined to be adequate and the
recommendation is to keep the existing infrastructure in place. The ponding area sits on a single parcel of land which the City of Lawrence currently owns for use as a flooding easement.
Link to Cost estimate: System 11
Link to
diagram: Internal Analysis, System 11
12. System 12
This
system has a gravity flow outlet through the Kansas River levee for approximately a 7 acre area. The
pipe was analyzed with regard to capacity during a 10-year flow event. It
was determined to be adequate and the recommendation is to keep the existing
infrastructure in place. As no changes are recommended, the map for
System 12 does not have any callouts.
Link to Cost estimate: System 12
Link to
diagram: Internal Analysis, System 12
C. System
Naming Convention
To
represent the location of each component within its respective piping network
or system, a unique identification was provided. These designations are
utilized within the GIS database and the XP-SWMM models. An “S”
designation followed by a number is representative of the “System” that the
component is within. An “L” refers to the “Lateral” within the specific
system that is branching off of the main stem. A “T” refers to
“Tributary” and represents the branch coming off of the lateral within the
system. All numbers are consecutive and were labeled from downstream to
upstream. A final number after a dash is simply the pipe or channel
number. Two examples of the naming convention are provided below:
S1L2T1-2
identifies a component that is in System 1, Lateral 2,
Tributary 1, and Pipe/Channel number 2
S6L6-10
identifies a component that is in System 6, Lateral 6,
and Pipe/Channel number 10
D. Hydrologic and Hydraulic Analyses
The
hydrology of the watershed is defined by the rainfall-runoff process.
APWA Section 5600 requires that the Rational Method be used to calculate peak
rates of runoff to elements of enclosed and open channel systems, including
inlets, when the total upstream area tributary to the point of consideration is
less than 200 acres. The internal system analysis utilized the Rational
Method to produce the 10-year frequency peak flow rates throughout the
watershed. Rainfall was determined from an existing
intensity-duration-frequency table. The runoff process is defined by the
rainfall rate and a number of other factors including infiltration rate,
percent impervious and slope of the land. All of these factors are site
specific and can vary from sub-area to sub-area.
The XP-SWMM (StormWater Management Model) software
(Version 9.5) was chosen as the primary tool for evaluation of the drainage
system internal to North
Lawrence. This
program provides the necessary flexibility, ease of use, technical support of
the company that developed the software, and the ability to integrate the GIS
data.
The modeling software is modular which allows the user to choose the packages
to be used for a particular model that has been created. For the
watershed event simulation, the Runoff Block and Transport Block are
used. The intensity-duration-frequency table, along with the
characteristics of each sub-area, is used to calculate the individual runoff
quantities. In the routing method of the Runoff Block, the Rational
Formula applies a simplified timing technique based on the time of concentration
for each sub-watershed to produce the complete hydrograph.
The Transport Block uses the results of the Runoff Block to route the
hydrographs through the drainage system. The system hydraulics is defined
within this module, which is used to identify system deficiencies. The
hydraulic layer uses a dynamic wave routing system with a variable time step
for the system.
1.
Hydrologic Parameters
A
rainfall intensity table for Douglas County, Kansas is provided as part of the Stormwater Management Design Criteria for the City of Lawrence. This table is included at the end of this
section and was used to determine intensities for the design storm event in
each of the various sub-watersheds. The total rainfall for a 10-minute duration is about 1 inch, whereas the total
rainfall for a one-hour storm is about 2.5 inches for the 10 year chance of exceedence event.
The
infiltration rate is a function of the moisture contained in the soil and the
soil type. If a soil is saturated from recent rains, the amount of
infiltration will be low as compared to a dry soil. The soil type also
affects infiltration rates because certain soils will pass water more readily
than others. In the North
Lawrence watershed, the Wabash, Kennebec, Reading,
Eudora and Kimo series are the primary soil
types. The Wabash-Kennebec-Reading soils are classified as types B, C and D, which is a silt loam with a minimum infiltration rate of 0.06 to
2.0 inches per hour. The Eudora-Kimo soils are
classified as types B and C, which is a sandy loam with a minimum infiltration
rate of 0.6 to 2.0 inches per hour.
The
type of land use is one of the most important factors controlling the amount of
runoff from a watershed. The internal drainage analysis concentrated on
the ultimate build-out condition in order to assess adequacy of infrastructure
components. Refer to Section III of this report for details on the
development of the Build-Out Scenario Map. The map provides land use
categories which were related to Rational Method runoff coefficients through
the use of various sources. The sources include:
- Land use assumptions in this report
- Horizon 2020
- TR-55 (Urban Hydrology for Small Watersheds from
the Natural Resources
Conservation Service)
- Lawrence Drainage Criteria
- APWA 5602.2
The
runoff coefficient, “C”, considers the percent impervious and infiltration
aspects of the watershed in a single value. The following table relates
the percent impervious and corresponding Rational Method “C” value to the various land uses specified.
Land Use Hydrologic Parameters
![](N_Law_Drainage_Study_2005_files/image007.gif)
The
link between GIS and the XP-SWMM model made it possible to enter many of the
parameters into the model directly from the database and mapping. After a
significant effort to compile a complete, consistent map and database for the
internal system, the GIS environment was used to delineate the sub-areas and
develop time of concentrations. The downstream boundary of each sub-area
was either at an inlet (or a manhole receiving flow from inlets) for the
enclosed system, or a structure or confluence with a tributary for the open
channel system. The delineated size of each area could be calculated from the
polygons created during delineation. The length and slope parameters of
overland flow and concentrated flow were determined in ArcView
for use in a spreadsheet application.
The
calculated time of concentration, TC, is equal to the overland flow time to the most
upstream inlet or other point of entry to the system, Inlet Time, TI,
plus the time for the flow in the system to travel to the point under
consideration, Travel Time, TT. TC = TI + TT. The inlet
time was calculated per the equation in section 5602.7, ensuring the inlet time
was not less 5.0 minutes and not greater than 15.0 minutes. Travel Time,
TT, was calculated as the length of travel in the channelized system divided by the velocity of flow.
The velocity of flow was calculated by Manning’s equation assuming all system
elements are flowing full without surcharge. Manual Rational Method
calculations were performed for each sub-area within the watershed to verify
accuracy.
A
composite “C” value for each sub-area delineated during the
internal analysis was created by utilizing the intersect function in ArcView. The future land use types were essentially
placed on top of the drainage areas and dispersed. A breakdown of the
percentage of each land use within a respective area could be obtained.
Those percentages were then applied to the “C” values shown above for a weighted value.
The
following hydrologic parameters were ultimately imported to the XP-SWMM
modeling software:
- Drainage Area
- Runoff coefficient
- Time of concentration
2.
Hydraulic Parameters
The
existing drainage system components required physical characteristics such as
conduit or channel size, conduit or channel length, and roughness. In
addition, flowlines were needed for channels, pipes,
manholes, and junction boxes. Most of this data was acquired from survey
or existing City GIS. A relatively small number of values
were interpolated or assumed – those interpolations and assumptions are noted
in the final database.
Before
transferring the database information to the hydrologic model, it was necessary
to create the system in a spatially correct manner. Connectivity of the system was determined by combining the sources of
data and creating the single, integrated GIS map. With that in place,
coordinates of the manholes, inlets, and junction boxes were used to create the
XP-SWMM model “nodes”. The reliable connectivity allowed the direct
transfer of pipe locations as “links” into the model.
Pipe
and channel roughness values (Manning’s “n”) were determined using APWA 5600
and the Lawrence Stormwater Management Design Criteria. They were verified with field observations, aerial
photographs, and engineering judgment. The following table shows the
roughness values used to represent the piping and channels within the model.
Conduit Type
|
Manning’s “n”
|
Concrete Pipe
|
0.013
|
Reinforced Concrete Box
|
0.013
|
Corrugated Metal Pipe
|
0.024
|
Concrete Channel
|
0.013
|
Grass Channel
|
0.05
|
The
following hydraulic parameters were ultimately imported to the XP-SWMM modeling
software:
- Conduit or channel dimensions
- Conduit or channel length
- Conduit or channel flowlines
- Manhole, inlet, and junction box flowlines
- Conduit roughness
Link to: Stormwater Management Design Criteria: Rainfall
Intensity Table
Section VI: Watershed Analysis
A. Overview
The
North Lawrence Drainage Area is comprised of approximately 9100 acres (14
square miles), 7.9 square miles of which drain into the Kansas River through a structure in the levee along Mud Creek. This is located on the eastern edge of the drainage basin,
just north of E. 1700 Road, in Leavenworth County.
The North Lawrence Drainage Area is bounded by high ground on the north and a
federal levee system providing protection from the Kansas River on the other three sides. There are also
approximately 1.8 square miles of area, in the southwest portion of the basin,
that are drained through other levee openings in that
area. Those systems are addressed in the Internal Drainage System
Analysis section of this report. There is approximately 0.6 square miles
of overlap between the two systems along the western edge of the basin.
North of 24/40 Highway and west of the airport, 3.1 square miles currently drains
to the 2nd Street Pump Station in the Internal Drainage System, but
the capacity of this station is quickly exceeded during significant storm
events. A main focus of this section of the report addresses that
issue. The purpose of this section is to explore methods of flood
reduction, the consequences of development in the area and to provide
recommendations for future development. Maps detailing the hydrologic and
hydraulic configuration of the watershed and the recommended alternatives can
be found throughout this section.
B. Recommendations
There
were three main goals of the improvement alternatives: To reduce the
demand on the 2nd
Street Pump
Station, to expel floodwater from the basin during times of high water on the Kansas River and to investigate the effects of development in the
floodplain. With regard to reducing demand on the 2nd Street Pump Station, it was decided in preliminary meetings
with the City that building additional gravity flow structures through the levee was not a feasible
option. This left pumping and diversion as usable methods for this
problem. Due to the topography of the basin, the area north of 24/40
Highway was deemed as the most suitable for both. This is a large and
currently undeveloped area that drains to the 2nd Street Pump Station. It is recommended that the
drainage from this area be cut off by the highway embankment and the water
pumped over the levee. The existing 24/40 Highway profile is not high
enough to contain the 100-year flood elevation for either the existing
conditions or the improved scenarios, so if this level of containment is
desired, that roadway profile would also need to be raised. The
recommendation for reducing the burden on the 2nd Street Pump Station appraises the 10-year event in
conjunction with the design criteria of the Internal System,
however the 100-year event is investigated as well. Detailed descriptions
of the different scenarios and a summary of the potential costs of each
scenario can be seen in the Section E.
The
recommended alternative is to block the flow from north of 24/40 Highway and
pump it over the levee at a point just east of the 24/40 intersection.
This will accomplish two things. It will reduce the demand on the 2nd Street Pump Station, which will lessen the flooding in the
currently populated area of North
Lawrence, and it will
reduce the overall volume of flood water that flows east towards the Mud Creek Levee during large events. This is not the natural path for
this water, so cutting off the flow from north of 24/40 Highway should reduce
the burden on this system. The pumping option is recommended over other
alternatives because volume reduction is one of the most viable ways to address
flooding in North Lawrence and the solution can be phased in as development
occurs. The pump station will consist of multiple pumps and can be built
in stages. Even cutting off the flow from north of the highway could be
done a piece at a time. The most likely sequence would be raising the
road west of the 24/40 intersection to create the ponding
reservoir and build a few pumps, then reconfigure the culverts at the 24/40
intersection, then remove the culvert that carries Maple Grove East under 24/40
Highway, etc., all the while increasing the capacity of the pump station as
more water is diverted to the ponding area.
This will ease the burden on the City budget and
could even be financed with some type of fee on developers, matching
expenditures to the need for improvements at that time. It should also be
noted that the ponding area will not flood any land
that is not already flooded during high flow events. It should also be
noted that the diversion option that was investigated would have had a lower
over-all construction cost, but would have had to be constructed all at once
and would have required cutting through some highly developable properties
along 24/40 Highway, east of the intersection.
The
recommendation for future development in the watershed is to maintain the
current conveyance levels in the 100-year floodplain. This will mean
allowing no development in these areas that would reduce the capacity for
floodplain storage, and may require the purchase of small parcels of land to
set aside exclusively for ponding. Methods of
mitigation for blockage of or fill in the floodplain are impractical or of
questionable value. Due to the flat topography and the lack of a proper
conveyance path that extends all the way to the outlet at Mud Creek, locally increased channel areas would be of limited effectiveness,
require regular maintenance and would require large scale cooperation and long
term planning with the various property owners, developers and the City. Even if those things could be accomplished, hydraulic
controls near the lower end of the watershed are owned by railroads or are in Leavenworth County,
which places them beyond the ability of the City to control. In general, the nature of this drainage area
dictates that the current floodplain storage be maintained.
As
the area develops, it will become necessary to provide emergency services to
the homes and businesses that populate the area. This will require the
improvement of the major roads in the area and significant improvement of the
hydraulic structures which carry flow under the roads. Currently, the roads are not raised far above the floodplain and the
hydraulic structures are relatively small. The result of this is that
there is significant overtopping of the road during times of high flow.
During such times, it is very dangerous, if not impossible, for emergency
vehicles to traverse these roads. With a dense urban population, this
will become unacceptable. Therefore, the roads will not only have to be
improved to increase traffic capacity, but will have to be raised to meet the
current APWA criteria with regard to overtopping during the 100-year
event. By raising the road, it cuts off the large amount of water that
used to flow across the lower roads. It is therefore necessary to provide
hydraulic structures capable of passing that large amount of additional flow,
while not increasing water surface elevations upstream. This results in
some significant increases in required flow capacity over the existing
hydraulic structures.
In
an effort to quantify the various issues confronting North Lawrence, several hydraulic and hydrologic models were
created. The sections below detail those modeling efforts and a detailed
examination of the alternatives follows.
C.
HEC-1
Model Development
1.
General Project Information
Rainfall runoff, overland flow, and channel flow processes for the North
Lawrence Drainage Study were simulated using the HEC-1 program developed by the Army Corps of Engineers. The model provides an estimation of the timing
and volume of flows as well as the peak discharge at selected locations within
the watershed. The HEC-1 program
also allows for modeling of storage or backwater to assist in the calibration
of the peak flows to field conditions. The peak flow is used in the
hydraulic modeling to produce the water surface elevations of the
floodplains. This chapter describes the methods and development of the HEC-1 models for the North Lawrence Drainage Study.
2. Data and Model Development
Data and model development includes the process to determine the shape, size,
sub-area break down, and hydraulic conveyance of the entire watershed.
The data sources used were:
·
2-foot contour map provided by the City
·
USGS contour map of the area
·
Field surveys
Best professional
engineering judgment in conjunction with industry-accepted practices was used
in interpreting the data sources. From the above sources, data was collected
and the input information for the hydrologic model was created. The watershed
characteristics found using the maps are bulleted below
- Sub-area boundaries
- Sub-area flow paths and slopes
- Channel flow lengths and slopes
3. Input Parameter Development
Input Parameter development includes the collection and subsequent input of
watershed characteristics into the HEC-1 modeling program. These input parameters are:
- Sub-area size (square miles)
- Curve number (CN) as it relates to future land use
- Lag time (Tlag) – is a
characteristic of the watershed, which is defined as equal to the time
from the center of mass of the excess rainfall to the time of the
peak. The HEC-1 program assumes this relationship to be: Tlag = 0.6*Tc, where Tc is the time of concentration.
- 8 point representative channel cross section for
the computation of Muskingum-Cunge channel routing.
Sub-area Size
Sub-area
boundaries were determined using contour maps, but sub-area size was measured
with ArcView GIS software. The
average sub-area size was approximately 150 acres. The acreage of each
sub-area was dependent upon its proximity to the location of confluences and
structures.
Curve Number
The Build-Out Scenario Map was assigned Curve Numbers for each land use. ArcView used
the land use and sub-areas coverages to determine which
future land use polygons were contained in each sub-area. The future land
use polygons contained within a sub-area boundary were labeled with the
sub-area name and the area of each land use was calculated. A curve
number was associated with each of these land uses and a weighted curve number
was computed in a spreadsheet. Curve numbers are shown below.
Curve Numbers
![](N_Law_Drainage_Study_2005_files/image008.gif)
Lag
times for the watersheds were found using the relationship Tlag
= 0.6*Tc, where Tc
is the time of concentration. The time of concentration was found using the
Stormwater Management Criteria Manual of the city of Lawrence. The City defines
time of concentration as the sum of the overland flow time, the shallow
concentrated flow time and the channel flow time. Table D and Figures 1 and 2
from the Stormwater Management Criteria Manual
were used to find these times respectively. Some sub-areas were extremely flat
and a value could not be read off of Figure 2 to determine the channel flow
time. In these instances, a minimum velocity of 1.5 feet per second was assumed
to estimate the channel flow time.
4. Naming Conventions
First order tributaries are streams that flow directly into the Kansas River,
second order tributaries flow into first order tributaries, third order
tributaries flow into second order tributaries and so on. One first order
tributary and two second order tributaries were named on the current FEMA FIRM
maps. These names were retained in the naming scheme for the hydrology
and hydraulic models.
The
HEC-1 program is a DOS program based on 8 character
sets. The first two characters “KK” indicate a HEC-1 hydrograph calculating routine in which the last six characters are a
unique identifier for that routine. A five-character name identifier
followed by a one-letter modeling descriptor was used in the HEC-1 model for the North Lawrence Drainage Study.
Name Identifier
In
order to represent the location of each sub-area relative to its location on
the stream network, one character was used for each tributary (first through
fourth) downstream of the sub-area being named. Along each stream, the
sub-areas were then numbered (1, 2, 3, etc.) starting from the upstream end and
proceeding downstream. Specific details about the HEC-1 naming at each tributary level are given in the following sections.
First
Order Tributary
There
is one first order tributary located in the study area. The tributary
name is listed below with the single character identifier used in the HEC-1 naming convention.
M
Maple Grove Drainage
Second
Order Tributaries
The
four second order tributaries were named in one of two ways. Two of the
second order tributaries have names on the current FEMA FIRM maps, Maple Grove
East Fork and Maple Grove West Fork. In these instances either
"E" or "W" was used as a second order identifier. The
remaining tributaries were then named alphabetically (a, b) starting from the
downstream end of the first order tributary they flow into. In the HEC-1 naming convention, the sub-areas going to a second order tributary
use two characters to identify them. The first character is the first
order tributary name and the second is the second order tributary name.
Each second order tributary name is listed below with the two-character
identifier used in the HEC-1 naming convention.
ME
Maple Grove Drainage East Fork
MW
Maple Grove Drainage West Fork
Ma,
Mb Tributaries Maple Grove Drainage
Modeling Descriptor
The
last digit in the HEC-1 naming convention describes the hydrograph
calculation process that the HEC-1 program is
doing during each hydrograph calculation routine. The hydrographs are
either (1) being created from the drainage basin, (2) being routed through a
channel to a downstream location, or (3) being combined with other drainage
basin hydrographs. The key for the single digit modeling descriptor is
shown in the table.
Modeling Descriptor Key
Descriptor
|
Hydrograph Calculation Routine
|
Remarks
|
A
|
Drainage Area
|
Hydrograph calculated from
sub-area characteristics and precipitation inputs.
|
R
|
Routing
|
Hydrograph routing through
channels.
|
L
|
Local Combine
|
Points where hydrographs
along a single stream are combined.
|
T
|
Tributary Combine
|
Points where tributary
hydrographs are combined together to get total flow at a junction.
|
In the HEC-1 model, the modeling descriptor is attached to the name
identifier. Some examples of a complete unique identifier used in the
Maple Grove Drainage watershed are as follows:
MW_1A
Drainage area routine for Basin “1” of Maple Grove West Fork
to Maple Grove Drainage
ME_7L
Combine multiple hydrographs at the downstream point
of Basin “7” of Maple Grove East Fork
M_7T
Combine tributary hydrograph with Maple Grove Drainage
hydrograph at the downstream point of Basin “7” of Maple Grove Drainage.
Mb_3R
Channel routing routine for Basin “3” on Trib “B” to downstream point of Basin "4" on Trib "B".
5. Hydrologic Methodology
For the North Lawrence Drainage Study, a 24-hour Type II design storm was
utilized. The rainfall depths for the storm event were obtained from the
Rainfall Frequency Atlas of the United States.
Rainfall Depths (inches) For a Type II 24-hour
Duration Storm
Duration
|
Return Period
|
2 yr
|
5 yr
|
10 yr
|
25 yr
|
50 yr
|
100 yr
|
24 hr
|
3.49
|
4.59
|
5.31
|
6.15
|
6.88
|
7.7
|
The
North Lawrence Drainage study required storage routing behind Highway 24 at the
East and West Fork confluence and at the downstream end of Maple Grove drainage at the Union Pacific Railroad. The dam
routine in HEC-1 was utilized. Elevation-area and
elevation-discharge data was developed. The rating curve
(elevation-discharge data) was developed from the HEC-RAS model. A range of flows was entered into HEC-RAS for the tributary with the structure requiring storage
calculations. The resulting water surface elevations versus the
discharges were then recorded and entered into a spreadsheet to create the
rating curve. Values from this curve were then entered into HEC-1. The peak elevations from the HEC-1 model output were then compared to the HEC-RAS developed curve again to make sure that the modeled structure and
the hydrologic model were producing similar water surface elevations for a
particular peak flow.
2nd Street Pump Station
The
2nd Street pump station consists of two pumps each with a
capacity of 45 cfs. The pumps are located on 2nd Street in the south western part of the study area. The HEC1 flows were reduced by 90 cfs where
appropriate before entering them into the HEC-RAS model to account for the pump station.
6.
Model Comparison
The new HEC-1 model results were compared to the flows that are
published in the FEMA study. This data is only available for Maple Grove drainage and East and West Forks. The
comparison is shown in the table.
Previous Flows versus Restudy Flows (cfs)
|
FEMA Study/North Lawrence Drainage Study
|
|
2 yr
|
5 yr
|
10 yr
|
25 yr
|
50 yr
|
100 yr
|
Maple
Grove
Drainage
|
|
|
|
|
|
|
At Douglas-Leavenworth County line
|
450
|
774
|
2190/1160
|
1548
|
3730/1893
|
4490/2348
|
1,400 feet upstream of
Interstate 70
|
344
|
526
|
1450/741
|
947
|
2470/1126
|
2960/1337
|
At Ninth Street
|
428
|
630
|
1280/849
|
1068
|
2180/1265
|
2610/1510
|
Upstream of confluence with
Maple Grove Trib.
|
323
|
498
|
1030/723
|
935
|
1750/1118
|
2100/1315
|
Maple
Grove
Drainage East Fork
|
|
|
|
|
|
|
Below U.S. Highway 40
|
256
|
362
|
559/496
|
633
|
952/745
|
1140/879
|
Downstream of County Road 173/1900
|
201
|
294
|
292/406
|
515
|
497/602
|
592/707
|
Maple
Grove
Drainage West Fork
|
|
|
|
|
|
|
Below U.S. Highway 40
|
406
|
632
|
559/894
|
1154
|
952/1365
|
1140/1631
|
The difference between the
flows from the two sources is the methodology used to calculate them.
This study calculates flows based on the unusual characteristics specific to
the North Lawrence Drainage Area. The FEMA Study uses equations developed
by regression analysis using general characteristics common to streams of all
sizes from across the entire region.
Link to
diagram: Watershed Analysis: HEC-1
D. HEC-RAS
Model Development
1.
General Project Information
The
HEC-RAS, version 3.1.1 hydraulic model was used to
produce water surface elevations along each stream. The information
required to build a hydraulic model is as follows: hydraulic characteristics of
culverts, bridges, dams, low water crossings, and open channels, in conjunction
with the peak flows determined in the HEC-1 model. This model was developed for the Maple Grove Drainage
system, ignoring influence of the Kansas River.
2.
Data Sources
Data
and model development includes the process to determine the primary stream
network, cross section geometry, flow lengths, bank stations, and Manning’s “n”
values for the entire watershed. The data sources used were:
·
Planimetric information in GIS format provided by the City
·
Topographic information provided by the City
·
Digital elevation data in the form of a
triangular irregular network (TIN) generated using GIS and topographic
information
·
Aerial photographs provided by the City
·
Field surveys of stormwater drainage
structures and roadways provided by Landplan
Engineering of Lawrence
·
Current FEMA HEC-2 model prepared by GBA
Best professional
engineering judgment in conjunction with industry-accepted practices was used
in interpreting the data sources.
3.
Input Parameter Development
From
the above sources, data was collected and the input information for the
hydraulic models was created using GeoRAS, an ArcView extension that compiles GIS data into an input file
for the HEC-RAS model. The development of these input
parameters is described individually in the following sections.
The
primary stream network was developed using ArcView.
The network includes channels that are fed by a drainage area of 240 acres or
more. Small “stubs” or tributaries that are not long enough to place
three or more cross sections along the stream were removed from the HEC-RAS model because the short distance is usually controlled by the
receiving stream and mapped at that water surface elevation.
Naming Convention
Four
separate streams were modeled in HEC-RAS. The first order tributary and two of the second order
tributaries were named on the current FEMA FIRM maps. These names were
retained in the hydraulic model. Maple Grove West Fork was combined with Maple
Grove Drainage to model a continuous main stream. The remaining two second
order tributaries were named alphabetically.
First
Order Tributary
There
is one first order tributary located in the study area. The tributary name
is listed below with the identifier used in the hydraulic model
Maple Grove
Maple Grove Drainage combined with Maple Grove West Fork
Second
Order Tributaries
There
are four second order tributaries in the study area. Maple Grove West
Fork was combined with Maple Grove Drainage and the remaining three tributary
names are listed below along with the identifier used in the hydraulic Model
MG
East Maple Grove East Fork
Trib A
Tributary A to Maple
Grove Drainage
Trib
B
Tributary B to Maple
Grove Drainage
Cross-Section
Development
A
cross section shape-file was created using ArcView. Cross sections were generally placed 200 to 500 feet apart along each
stream centerline. Near structures, the cross sections were placed as
recommended in the HEC-RAS modeling manual. A section was placed off
of the embankment at the upstream and downstream face of each structure.
Two more sections were then placed a distance upstream and downstream of the structure
where the flow is fully expanded. Cross sections were drawn to best represent the channel and floodplains
in the area. GeoRAS used this coverage to
intersect the stream centerlines, flowpaths, and
locate the TIN elevation that represents the ground surface in the HEC-RAS model.
Flowpath Lengths
A
flowpath lengths shape-file was created for use in
the GeoRAS export. The flowpaths
follow the stream centerline at a distance to the right or left where
approximately two-thirds of the water in the floodplain is contained. GeoRAS used this coverage to create left and right overbank reach lengths. GeoRAS
used this file to create the geometry export file for HEC-RAS.
Manning’s
“n” values were determined using field observations, aerial photographs, and
engineering judgment. The values were entered directly into the HEC-RAS model. The following table shows the Manning’s “n” values
used to represent the common groundcover or land use conditions.
Overbank Manning’s “n” Values
Groundcover condition
|
Manning’s “n”
|
Trees
|
0.10
|
Moderately treed
|
0.08
|
Crops or grassland
|
0.04
|
Natural Channel
|
0.045
|
The Manning’s “n” values for
the channels in the North Lawrence Drainage study follow the trends
shown. Some values may be slightly different in the HEC-RAS models due to engineering judgment of a specific location.
Structure Manning’s “n” Values
Structure Material
|
Manning’s “n”
|
Concrete
|
0.013
|
Corrugated Metal
|
0.021
|
Steel
|
0.013
|
Manning’s “n” values of
structures were mainly determined by field observations. The guideline
tables in the HEC-RAS manual were generally followed. Specific
material type and Manning’s “n” values are shown in the table above.
Structures
at roadway crossings were entered directly into the HEC-RAS model. The cross sections upstream and downstream provided by
GeoRAS were supplemented with survey
information. This allowed for a more accurate representation of the
channel and structure opening at roads and railroads. Road and railroad
structures were mostly created by using field observations, photographs, and
survey data. If the survey information along the roadway surface (deck)
did not extend the length of the upstream and downstream cross sections, the
elevation along the remaining length was determined using the contours provided
by the City.
Modeling methods and
parameters for each structure (such as Chart and Scale # for culverts or energy, momentum, Yarnell’s
equation for bridges) were determined using field observations, photos, and
engineering judgment. Coefficients
used for each modeling method were chosen from the tables provided in the HEC-RAS manual.
Expansion/Contraction Coefficients
Channel Bank
Stations
The
water surface elevations were very similar to the published FEMA values,
despite the significantly lower discharges. This can be explained by the
extremely wide flat floodplain with very little to no slope. Also,
the significantly undersized culverts remain unchanged and are a controlling
factor in the water surface elevation. Differences of one foot or more
are listed below.
Maple
Grove
Drainage: The water surface elevation for the area between North 9th Street and North 7th Street decreased from approximately 821.5 ft to 820.0
ft.
Maple
Grove East
Fork: The water surface elevation at the mouth decreased from approximately
823.75 ft to 822.65 ft.
Maple
Grove West
Fork: The water surface elevation for the downstream portion increased
from approximately 823.0 ft to 824.2 ft.
E. Alternatives
for Future Development
Several alternatives were investigated to alleviate flooding problems in the North Lawrence watershed. Some had greater or lesser merits
and some proved impractical altogether. Detailed below are some of the
alternatives considered. Not all are included in the
recommendations.
The External System was modeled as one main reach, extending from the Mud Creek Levee up through the northwest-most contributing area, and three
tributary streams: Tributary A, just south of the airport; Tributary B,
in the southeast portion of the basin; and Maple Grove East, just west of the
airport. It should be noted that this is not a well defined stream
throughout its entire length. During low flow events, water may pond and
infiltrate or flow back towards the Internal Drainage System. During high
flow this represents the flow path, with the lower five miles of the main reach
coinciding with the FEMA floodway. It should be noted however, that this
is not the natural flow path for the waters west of the airport. Refer to
the accompanying maps for further clarification of the hydraulic and hydrologic
configuration of the basin.
While the details of the modeling are discussed in previous sections of this
report, there are a few key features pertinent to the alternatives discussed
here that should be reiterated. This entire area is very flat, which
results in significant ponding until enough hydraulic
head can develop to push the water downstream. When the water does begin
to flow, it has relatively low velocities. There are major hydraulic
constrictions near the Mud Creek
levee. Two of them are undersized structures through railroad
embankments, which place them beyond the scope of this study to
remediate. There is also the roadway embankment along 7th Street (1500 Road) and the high ground between there and 9th Street that has a significant effect on the hydraulic
profile upstream. Several scenarios were investigated for alleviating the
potential flooding in this area, but the topography of the basin prevents
significant improvements in flood elevations on a large scale.
1. Flood Reduction Alternatives
As
stated earlier, the cornerstone to the recommendations in this report is greatly
reducing the burden on the 2nd Street Pump Station. This is to be accomplished by
cutting off the flow from north of 24/40 Highway. This is a relatively
large and currently undeveloped area that has the potential to add a great deal
of volume to the existing flooding problem when developed.
A
diversion channel was modeled along 24/40 Highway, from near the 24/40
intersection, east to connect with Tributary A near Airport Road. This would require the existing 6’x4’ culvert
that runs diagonally under the 24/40 intersection and the 36” culvert that
drains the area to the northeast into the intersection be removed or greatly
reduced in capacity to remove the flow from the 2nd Street Pump Station or allow only low flows to travel that
path, as they do now. A new east-west 2-6’x5’ culvert would be built
under 24 Highway, north of the intersection to connect the northwest area to
the diversion channel. Another 2-12’x10’ culvert would be built to carry
the diversion channel under 1500 Road. The diversion channel would be a
trapezoidal channel with 3:1 side slopes and a five foot bottom width.
The channel would have to flair out to match up with the 1500 Road culvert, and
includes a high flow bench on the north side near the eastern end to allow a
smoother transition to the Tributary A channel.
This scenario would also require the elimination of the 6’x5’ RCB that currently carries Maple Grove East Tributary under 24/40
Highway. Unfortunately, this channel would have to be aligned through
some of the highest ground in the entire basin, resulting in a deep and wide
channel with approximately 90,000 cubic yards of excavation, which would result
in construction costs on the order of $2.5 million.
Another
method of dealing with the excess water from the northwest areas is to pump it
over the levee. The culverts at the 24/40 intersection and the Maple
Grove East culvert would be removed and the new east-west culvert under 24
Highway would still be required, as in the diversion option described above.
A large area north of 1800 Road and east of 24 Highway would become a pumping
reservoir, ponding to an elevation of approximately
822 feet for the 10-year and approximately 825 feet for the 100-year. It
should be noted that the elevation at the intersection of 24 and 40 Highways is
approximately 822 feet. To contain the 100-year event, would require
raising 24/40 for approximately 2000 feet east of the railroad and 24 highway
for approximately 1000 feet north of the intersection, at a cost of approximately
$800,000. This ponding area could be reduced by
building berms to protect certain areas and/or
increasing pumping capacity to compensate for the loss of storage.
Another alternative would be to build two pump stations. One at the
current site would function in a reduced capacity, while another east of 24/40
Highway would pump the water from Maple Grove East directly over the
levee. This would require a berm to capture the
water and would probably be more expensive overall, but could be justified if
property costs and location dictate the design. The cost for the pumps
and controls to handle the 10-year flow, approximately 800 cfs,
would be approximately $1.7 million. To pump the 100-year discharge, the
cost would increase to approximately $3.0 million. Total costs for
pumping stations are highly variable, and depend on the level of redundancy
desired with regard to backup pumps, power supplies, outlet works, etc. and
ancillary components such as pump houses and inlet and outlet works.
Depending on the desired capacity and configuration, the total cost for the
station could exceed $10 million. Pump costs for this scenario are
independent of the Kansas
River elevation.
Because the system would route the water over the top of the levee, the total
system head would be controlled by the top-of-levee elevation.
An
investigation was performed to evacuate flood water from the basin during times
of high flow on the Kansas
River. Using
methodology developed by the Corps of
Engineers, for determining coincident flows based on the ratio of drainage
areas, it was determined that the coincident events for the North Lawrence
Drainage Basin and the Kansas River were the 100-year and the 4-year
events. This means that for a 100-year event on the Kansas River, you could expect a peak event equivalent to the
4-year event in the North
Lawrence basin, and vise
versa. The 10-year design for the northwest area described above would
have the capacity for that coincident event and, as noted previously, that
system is independent of the Kansas
River elevation in any
case. At the east end of the basin, where the discharge is by gravity
flow through the levee, a 100-year Kansas River event would require the closing
of the Mud Creek structure to prevent back flow from the Kansas
River. A pump station at that location to handle the 4-year event would
require approximately a 300 cfs capacity. The
pumps and controls for that facility would cost approximately $0.8
million. Once again costs for the associated facilities are highly variable,
but could cost approximately $4 million.
Of
these alternatives, cutting off the flow from the 2nd Street Pump Station and pumping it over the levee is deemed
the most feasible and as having the greatest benefit to the North Lawrence
Drainage Area. The diversion channel, while less expensive to construct,
would require a large section of developable property along more than half a
mile of 24/40 Highway. Additionally, it would result in only localized
improvements in flood elevations and would significantly increase flood
elevations in the lower portions of Tributary A, due to the hydraulic
restrictions discussed earlier. The pump station at the east end of the
basin is not recommended due to its cost and the statistical improbability of
the design event.
2. Future Hydraulic Drainage Improvements
As
the area develops, the need for uninterrupted transportation and emergency
services will increase. An investigation was undertaken to assess the
requirements for raising the major roads above the 100-year elevation and
building hydraulic structures that would pass the 100-year with out increasing
the backwater. A summary of the improvements and associated costs can be
found in the tables at the end of this section. In the North Lawrence basin there are approximately 5 miles of roads that
would fall under these criteria. To construct major arterial streets on
mostly borrowed fill and only across the 100-year floodplain and upgrade the
associated hydraulic structures to pass the flows without causing increased
flooding upstream would cost approximately $14.3 million. This does not
include ancillary items such as interface with other roadways, bridges, traffic
control devices, right-of-way acquisition, etc. There are fourteen
hydraulic structures on these roads in the current model. The cost of
each project is shown in the table at the end of this section.
There
has been some development in this area already and questions have arisen
regarding the effects of fill placed in the floodplain. A study was
conducted to assess the effects and determine a general mitigation strategy for
future development. In a test reach, a large area was blocked off in the
100-year floodplain to simulate development that might place fill in the area
to elevate the property above the 100-year flood elevation. While this
does not have a large effect on the flood profiles, due to the basin factors
already discussed, the cumulative effect of large scale development will have a
detrimental affect on the flood elevations upstream. Also a concern is
the reduction in routing storage. One advantage to the low hydraulic
gradient and low velocities in this system is a significant attenuation of
flood peaks as they move through the basin. If the flow is constricted,
it will reduce this phenomenon, resulting in increased peak flows. The
investigation revealed that restoration of at least 70% of the flow area lost
to fill, through overbank benching, would be required
to mitigate the increase in flood elevations. However, this would reduce
the routing storage and would require regular maintenance and large scale
planning and coordination to achieve the desired affect. While these
measures could theoretically maintain the 100-year flood elevations in the
basin, this methodology is not deemed practical as a watershed planning
program.
![](N_Law_Drainage_Study_2005_files/image001.gif)
3.
Summary
Several
alternatives were investigated in the North Lawrence Drainage Basin to reduce
flood elevations, lessen impacts on “Internal” facilities, provide drainage in
the event of high flows on the Kansas
River and assess the
effects of development in the floodplain.
The
recommended improvements begin with cutting off the flow from north of 24/40
Highway. This is necessary to reduce the burden on the 2nd Street Pump Station and the total volume of runoff flowing
into the Maple
Grove system.
While other options were investigated, the recommended alternative
is to cutoff the areas northwest of 24/40 Highway and then pump the
water over the levee. This option is desirable due not only to its
effectiveness, but also due to the fact that the solution can be constructed in
phases. A staged solution lends itself to fiscal flexibility for the City and the possibility of financing the project(s), or a specific phase
of the projects, with fees from developers as the area expands. For
instance, the City could pay to raise the roads and alleviate the
flooding in the airport area first, then development
could help to fund the increase in capacity necessary to account for the
increase in runoff caused by future development. Variations on the basic
configuration are possible in this area, including allowing low flows to
maintain their current path towards the 2nd Street Pump Station and increasing the pump station
capacity to handle the 100-year discharge.
Future
development in the project area will result in a need for improved
roadways. The mile-section roads were modeled as being raised up out of
the floodplain and fitted with hydraulic structures that resulted in no
backwater. As the area develops, it will be necessary to keep the floodplain
available for storage. Therefore no development should be allowed that
reduces the capacity of the floodplain to attenuate the flood peaks.
While
there are many options for improving the flooding issues in the North Lawrence
Drainage Basin, the nature of the drainage area make some solutions more
practical than others. This area lacks a well defined channel, at a
consistent gradient for a significant portion of its length.
Additionally, there are some significant impediments to conveyance throughout
the reach, especially in the lower portion near Mud Creek. While construction of countermeasures may be effective in
solving some of the problems, maintaining the existing storage volume will play
a large part in the future flooding patterns. The portion of the drainage
area in Leavenworth County faces the same kind of issues as described in
this report and future development will likely increase flow in that area as
well.
Link to
diagram: Watershed Analysis Alternatives
Link to
diagram: Watershed Analysis HEC-RAS
Link to
diagram: Maple Grove Cut-off
Alternatives
Section VII: Kansas River Floodplain Analysis
A. Purpose
The effective FEMA hydraulic model was revised to approximate the amount of
flooding that would occur in the North Lawrence area
in the event of a breach of the Kansas River levee
system. A “most likely” breach location was determined for the purpose of
this analysis.
B. Results
To determine the “most likely” breach location
the model was run with peak flows in excess of the 100-year storm to determine
the first place of overtopping. This was located in the northwest portion
of the study area, with a flow of approximately 375,000 cfs.
By comparison, the 100-year and 500-year flows are 240,000 cfs
and 347,000 cfs, respectively. A breach
location was also assumed downstream of the City of Lawrence, where the levee system would again be overtopped by
flood waters behind the levee.
The Kansas River water surface elevations with a levee breach
condition were compared to the FEMA elevations with no levee breach. At
the upstream and downstream ends of our study area the elevations were similar;
however, up to 5' decrease was observed just upstream of I-70. As
illustrated on the attached floodplain maps, this still results in significant
flooding in this area. On average, the 100-year Kansas River flood levels during a levee breach condition were 0
to 7 feet higher than the Maple Grove Watershed flood levels. Again,
these flood level were determined from a “most likely” scenario, but there are
numerous other breach scenarios that could exist.
C. HEC-RAS Model Development
1.
General Project Information
The
HEC-RAS, version 3.1.1 hydraulic model produces water
surface elevations along each stream. The information required to build a
hydraulic model includes hydraulic characteristics of culverts, bridges, dams,
low water crossings, and open channels. This model was based on the
original HEC-2 hydraulic model.
2.
Data Sources
Data and model development includes the process to
determine the primary stream network, cross section geometry, flow lengths, bank
stations, and Manning’s “n” values for the entire watershed. The data
sources used were:
·
Planimetric information in GIS format provided by the City
·
Topographic information provided by the City
·
Digital elevation data in the form of a
triangular irregular format (TIN) generated using GIS and topographic
information
·
Aerial photographs provided by the City
·
Current FEMA HEC-2 model prepared by GBA
Best professional
engineering judgment in conjunction with industry-accepted practices was used
in interpreting the data sources.
3.
Input Parameter
Development
From
the above sources, data was collected and the input information for the
hydraulic models was created using GeoRAS, an ArcView extension that compiles GIS data into an input file
for the HEC-RAS model. The development of these input
parameters is described individually in the following sections.
Naming Convention
Only
one reach was modeled. The Kansas River is named
in the FEMA FIRM map, and that name was retained in the HEC-RAS model.
Cross-Section Development
The
existing HEC-2 model was imported into HEC-RAS. The imported cross sections remained unchanged within the
levee. No significant discrepancies were found between the FEMA modeled
cross sections and the current mapping. By leaving the cross sectional
information unchanged, we were also able to make a true comparison of the FEMA
floodplain levels to that of the levee breach condition.
To
model the breach failure condition the cross sections were extended to the
northeast to the Mud Creek portion of the levee. The cross section
extensions were created using GeoRAS. These new
combined sections were used in the HEC-RAS model.
Flowpath Lengths
A
flowpath lengths shape-file was created for use in
the GeoRAS export. The flowpaths
follow the stream centerline at a distance to the right or left where
approximately two-thirds of the water in the floodplain is contained. GeoRAS used this coverage to create left and right overbank reach lengths. GeoRAS
used this file to create the geometry export file for HEC-RAS.
Manning’s “n” values
Manning’s
n values for the Kansas River model were imported from the HEC-2 model for the channel portion. For the extensions, a value of .04 was
used to model the area behind the levee (North Lawrence).
Roadway Crossings
Structures
at roadway crossing were imported from the HEC-2 model, including the bridge opening, roadway deck and position of the
bridge in the channel. Some minor modifications were made so the model
could be run in HEC-RAS.
Expansion/Contraction Coefficients
Boundary Conditions
Ineffective Flow Areas
Channel Bank Stations
Link to
diagram: Watershed Analysis Kansas River
Inundation