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STATEMENT
OF THE PROBLEM
Land within the City of Ashland, MO is being developed, changing
from agricultural to urban land uses. During the summer of 2000,
the City annexed land, doubling the size of the City. Urbanization
of agricultural land increases storm water discharges and the capacity
to transport contaminants from a watershed into the streams it feeds.
Portions of the City (including portions of the newly annexed land)
are located in the Bass Creek watershed, with Bass Creek eventually
running through losing stream segments (where the stream flows directly
to groundwater) and through Three Creeks State Park. Storm water
discharges need to be managed to meet regulatory requirements. In
addition, the endangered Topeka Shiner is present downstream of
Bass Creek.
In addition, the Environmental Protection Agency has promulgated
Phase II Storm Water Discharge requirements. The City as a separate
entity would not be required to comply with the storm water management
provisions because its population is below the regulatory cut-off.
However, because Ashland is located in Boone County, and Boone County
will be required to develop a storm water management plan, Ashland
may be required to participate in storm water management planning
as part of a County-wide effort to meet requirements.
PRESENT SITUATION
The City of Ashland currently performs minimal storm water management
planning because of it size (9500 population) and limited resources.
However, the City is experiencing rapid growth. The City is located
in the middle of the Columbia-Jefferson City corridor that is one
of the fastest growing regions in the state. Much of the rural land
in and around the City is targeted for development by private developers
in the near future.
NEW APPROACH &
POTENTIAL BENEFITS
The City of Ashland would like to develop a storm water management
ordinance. Maps and the results of computer model runs can be used
as part of the decision making process to evaluate alternative strategies.
Maps and computer model runs can be used to outline the nature of
the problem and the impact of various strategies at public meetings
and other forums.
Storm water management planning requires an accurate assessment
of current land use/land cover. In rapidly growing communities,
this assessment must be frequently updated. All this must be done
in a cost effective manner. Remote sensing is a new approach for
rapidly documenting watershed characteristics for storm water management
planning. Remote sensing combined with GIS can save labor and reduce
time of delivery of storm water modeling parameters required for
computer modeling as part of storm water management planning. Remote
sensing can also rapidly produce and update maps needed by public
officials in administering zoning and storm water management planning
and in presenting strategies at public meetings and other forums.
TECHNICAL APPROACH
TAKEN
The approach taken to provide input
information to City of Ashland management was to use a modeling
program commonly used to evaluate water quality in agricultural
areas (the latest version of the Agricultural Non Point Source model,
AGNPS 98). The program was modified to accept input data derived
from remote sensing whenever possible.
Davis and Wang (ICREST team members) produced a 30-m digital elevation
model (DEM) developed using digitally-scanned 1:40,000-scale National
Aerial Photography Program (NAPP) aerial photos in conjunction with
precision ground control. This DEM was used to delineate the Bass
Creek watershed, the collector/contributing channels feeding into
Bass Creek, and the subbasins into which the watershed is divided
based on the occurrence of contributing channels. IKONOS images
were not used to develop the DEM as they were not available when
the modeling effort was undertaken.
Corrêa and Adhityawarma (ICREST team members) produced the
land cover/land use classes required by AGNPS 98 using IKONOS multispectral
images with 4 meter spatial resolution available for the project
area. Land use/land cover for the Bass Creek area was determined
by supervised classification using a maximum likelihood classifier.
The area is mostly rural with a small diversification of land use.
Eight classes were mapped: fallow fields, small grain fields, legumes,
grass, woods, impervious areas, bare soil and water (lakes, ponds,
etc.).
Project participants used IKONOS land cover classifications created
for this project and the existing soil vector map to calculate an
aggregate runoff curve number for each of the watershed subbasins
based on existing conditions. Runoff curve numbers were used in
AGNPS 98 with other input parameters to calculate peak discharges
and sediment loads to the watershed outlet. The procedure was repeated
using different curve numbers representing alternative development
strategies.
Project participants examined sites within the City that are fully
developed in each of the City’s residential and commercial
zoning categories. From this examination, the percentages of each
land cover classification in a representative site were determined.
The percentages were used to calculate an aggregate assessment of
how development has occurred in the City of Ashland. That is, the
percentage of various land cover classifications that are found
in representative residential and commercial areas has been determined.
This represents how development has progressed in Ashland and may
be used as a surrogate for how the City will develop in the future
in a given zoning classification. The major importance of this task
is in determining the percent impervious area in residential and
commercial areas.
PRODUCTS
1. Map showing the Bass Creek watershed (with channels and subbasins
indicated) superimposed on an IKONOS image of the City, to indicate
to City officials and the public some of the information that is
now available from satellite imagery.
2. Map showing the Bass Creek watershed (with channels and subbasins
indicated) superimposed on an outline of the existing and recently
annexed property, to indicate those areas of the City potentially
impacting water quality in Bass Creek.
3. Map showing the Bass Creek watershed (with channels and subbasins
indicated) superimposed on a color representation of existing zoning,
as an indication of contributors to current sediment loads in Bass
Creek.
4. Map showing the Bass Creek watershed (with channels and subbasins
indicated) superimposed on a color representation of planned zoning,
both within the City limits and outside of the City limits, as an
indication of the potential contributors to sediment loads in Bass
Creek under the ultimate development scenario.
5. Map showing the Bass Creek watershed and City limits superimposed
on the current land cover classification.
6. Map showing the areas within the City that were taken to be representative
of the various zoning classifications (based on the recommendations
of the City’s consulting engineer). City-specific assessments
of land cover/land use are desired by the City so that planning
scenarios will represent how development is expected to take place
in Ashland, rather than being based on textbook assessments of how
development will progress.
7. Map and figures showing the satellite imagery used to develop
the land cover classification, and the land cover classifications
for City of Ashland R-1 developments.
8. Graphic displaying AGNPS 98 modeling results (sediment loads
delivered to the watershed outlet). Bass Creek watershed (with channels
and subbasins indicated) superimposed on an outline of the City
of Ashland, with colors indicating sediment loads to the watershed
outlet. The two simulations shown in this report are for sediment
loads based on existing land cover (current simulation) and assuming
all future urban residential development occurs with the same percentage
splits between R-1, R-2, and R-3 development as exist now within
the City. (R-weighted simulation).
INTEGRATION OF REMOTE SENSING DERIVED
INFORMATION INTO THE HYDROLOGIC MODELING
The project used remote sensing derived
data developed by other ICREST team members as some of the input
parameters of hydrologic modeling. The DEM used was produced Dr.
Curt H. Davis and Mr. Xiangyun Wang and the land use/land cover
classes used were produced by Dr. Aderbal C. Corrêa and Mr.
Janggam Adhityawarma.
LIMITATIONS
ON THE USE OF THE INFORMATION
The products from this project are intended to inform decision making
regarding the selection of stormwater management strategies. Field
data are not available to calibrate the AGNPS 98 model. Therefore,
the peak discharges and sediment loads calculated do not represent
exact flows and loads that would be measured in the field after
a rainfall event; however, they are appropriate to use in comparing
alternative development scenarios. For instance, outputs from a
number of alternative development scenarios will indicate the relative
impact of the alternatives on peak discharges and water quality.
The outputs as a whole can be utilized to determine those locations
most sensitive to development pressures and the potential benefits
that may be derived from implementing management strategies such
as limiting the percentage of a development block that may be covered
by impervious materials.
ANTICIPATED
IMPLEMENTATION PROBLEMS IN URBAN GOVERNMENT
The maps supplying information on the watershed boundary in relation
to the City limits and current and proposed zoning locations can
be utilized immediately and directly: (1) by decision makers to
identify potential areas of concern and (2) to show at public meetings
to increase awareness of storm water issues. Computer outputs can
be immediately and directly used by decision makers as they consider
storm water ordinance alternatives.
Ashland has only four City employees, and thus all engineering
analyses are currently performed by private consultants. The examination
of any additional development scenarios would have to be conducted
by consultants. If consultants are performing this function for
a number of small communities, then it can be developed for the
City in an economic fashion.
This information would be most useful to smaller communities who
do not have the resources to hire a consultant to perform a detailed
analysis of storm water impacts.
ADDITIONAL WORK
(1) Collect field data to calibrate AGNPS 98 for the Bear Creek
watershed.
(2) Perform additional AGNPS 98 runs representing alternative land-development
strategies.
(3) Because Ashland has no industrial areas, develop a surrogate
industrial area specifying the percentages of the various land use
classifications.
(4) Modify subbasins within AGNPS in order to be able to distinguish
the impact of the spatial locations of stormwater management strategies
(i.e., open space buffers adjacent to channels) on peak discharges
and sediment loads.
(5) Investigate nutrient and pesticide loads to Bass Creek.
(6) Investigate how this information can feed directly into developing
a storm water ordinance.
PROJECT PARTICIPANTS
Dr. Kathleen M. Trauth, Dr. R. Lee Peyton, Mr. D. Scott Adams, Dr.
Aderbal C. Corrêa, and Mr. Janggam Adhityawarma of the Center
for Environmental Technology (CENTECH), Department of Civil and
Environmental Engineering, carried out the project for ICREST
Figure 1:IKONOS Panchromatic with City of AshlandOutlined
Figure 2: Bass Creek Watershedwith City of Ashland Outlined
Figure 3: Current City Zoning
Figure 4: Planned City Zoning
Figure 5:Landcover Clasification and Location of The Training Area
using IKONOS Multispectral
Fig 6a: Residential Training Area Location
Fig6b: IKONOS Panchromatic
Figure 6c: IKONOS Multispectral
Figure 6d: Landcover Classification
Figure 7a. Current Simulation Figure 7b.
R-weighted Simulation
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