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