bsen 5220 case study: assignments 3 and 4 · case study: assignments 3 and 4 _____ manny norrell 29...
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BSEN 5220
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CASE STUDY: ASSIGNMENTS 3 AND 4
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Manny Norrell
29 October 2014
ABSTRACT:
Auburn University’s Ag Heritage Park is located on approximately 30 acres at the
southwest corner of Samford Avenue and Donahue Drive. The Park serves as a gathering place
for students, faculty, alumni and friends throughout the year. Ag Heritage Park is encompassed
by a 93-acre watershed that includes 45% semi-urban, impervious environment. Water routed
from the Ag Heritage Park drains into the Parkerson Mill Creek, a stream listed on ADEM’s List
of Impaired Waters. A possible method for improving the water quality of the creek is a storm
water wetland design.
INTRODUCTION:
Part of a storm water wetland design is delineating a watershed for an existing outlet. A
watershed can be delineated manually or with GIS software. Delineating a watershed is creating a
boundary that represents the contributing area for a particular control point or outlet. It should
encompass all areas that contribute runoff to the desired point, and is used to define the boundaries.
The goal of this lab was to delineate a natural watershed first and then one considering the
urban structures in the surrounding area. Completed contour maps and DEM from our previous
assignment were used to delineate the Ag Heritage Park watershed. Arc Toolbox and ArcMap was used
to delineate the watershed. Screenshots of the progress are presented in the Appendix. A natural
watershed map and a watershed considering storm water drainage pipes are shown in the Appendix.
PROCEDURES:
The objective of assignment three was to delineate the natural watershed of Ag
Heritage Park. The digital elevation model obtained in the previous lab was used to delineate a
watershed of Ag Heritage Park. Fill DEM tool was first used to eliminate any artificial highs or
lows in the elevation that could distort our flow direction. This made the DEM an essentially flat
surface with no sinkholes. Arc Toolbox was used to create a flow direction grid of the area.
Spatial Analyst toolbar was chosen and then Hydrology and Flow direction were selected. The
DEM was the input used. Next the Flow Accumulation layer was created once again using
toolbox. Spatial Analyst, Hydrology, and then Flow Accumulation were the chosen commands.
The new Flow Direction layer was selected as the input. Data Management tools were next
used to create a feature class. A point was created in the same AL East Projected Coordinate
System as the previous layers. Editor was used to move the point to the outlet location of Ag
Heritage Park just before the road. Snap Pour point was the selected to locate the outlet area
around the placed point. Finally the Hydrology tool in Arc Toolbox was selected and Watershed
was chosen. The required inputs were the Flow Direction layer and Snapped Pour Point. This
created the watershed that affects the outlet marked with the created point feature.
The objective of assignment four was to alter the natural watershed of the area to
compensate for the urban location and storm drain systems. Campus Base Map data was
downloaded and added to ArcMap. The previously created watershed was converted to a
polygon using the Conversion Tools in Arc Toolbox. From Raster was selected and then Raster
to Polygon. Once the watershed was a polygon it could be altered with the editor tools. The
watershed vertices were shifted to encompass the storm water drainage system and relate to
the flow of runoff from the urban areas. The lengths of the pipes were then added from the
attributes table.
RESULTS:
The first map in the Appendix is the natural watershed of Ag Heritage Park. Figure 1
shows a screenshot of the natural watershed overlaid on the Campus base map and drainage
system. Figure 2 is the watershed after being converted to a polygon. The polygon is selected in
editor and the vertices are highlighted and able to be moved manually. Figure 3 is a zoomed
view of the drainage system. The arrows display the direction of storm water flow. Figure 4 is a
screenshot of the watershed including the 2-foot contours and drainage pipe network of the
area. The second map in the appendix shows the edited watershed to include runoff from
storm water drainage system and man-made structures.
CONCLUSIONS:
The campus base map of urban structures, pipe system, and contours were used to alter
the watershed accordingly. The watershed was moved to include urban runoff and pipe
drainage. The impervious areas surrounding Ag Heritage Park do not allow precipitation to soak
into the ground. This greatly increases the volume of water flowing from the urban area. The
storm water drainage system can also divert the runoff away from naturally occurring flow
paths. Because of these reasons an urban location, such as Ag Heritage Park, cannot rely on a
natural watershed when creating a storm water wetland design. Arrows on the campus base
map annotated that runoff flow in the northeast corner of the watershed was diverted away
from the area to the east.
APPENDIX:
DATUM: NAD 83PROJECTION: TRANSVERSE MERCATORCOORDINATE SYSTEM: STATE PLANE AL. EAST
¯AG HERITAGE PARK STORM WATER WETLAND DESIGN
CREATED BY: MANNY NORRELLDATE: 10/27/14
0 500 1,000 1,500 2,000250Feet
LegendWatershed Boundary
1
729
794.6
515635
795.4
536.161
1.1
450.2
416.735
7.6
386.3
391.8358.9
320.3
301.7 309.4
372.9
291.2
261.8
316.6
245.9
343.5
217.2
94
421.2
201.1
132
414.8
203.119
0.8
71
171.6
144.8
140.1
181.9
171.8
97.9
95.18
118.4
DATUM: NAD 83PROJECTION: TRANSVERSE MERCATORCOORDINATE SYSTEM: STATE PLANE AL. EAST
¯AG HERITAGE PARK STORM WATER WETLAND DESIGN
CREATED BY: MANNY NORRELLDATE: 10/27/14
0 625 1,250 1,875 2,500312.5Feet
LegendStormwater DrainageWatershed