Presented to "Analysis of Urban Water Systems" (CIVE 572) at Colorado State University in Spring 2020.

1. Analysis of Stormwater System
for Urban Development Project
in North Louisiana
Spring 2020
CIVE 572 - Analysis of Urban Water Systems
BJ Elkins

2. Introduction

3. Pre-developed
condition

4. Post-developed
condition
Post-developed
condition

5. Statement of purpose
• The primary purpose is to analyze a stormwater drainage network
using EPA SWMM in comparison with the Rational Method used in
design. The pre and post developed conditions of the 23.6 acre site
have been analyzed.
• The secondary purpose is to propose alternative solutions for the
conveyance of runoff using the analysis from EPA SWMM.

6. Hypothesis
• EPA SWMM will result in a smaller discharge than the rational method
for both conditions because it accounts for infiltration and
evaporation.

7. Data collection
• Data provided by DeForest Engineering.
• CB drainage areas, lengths, and slope.
• Slope information.
• Land use areas.
• No groundwater flow (No USGS data for this area).

8. Methods
• ”As built” drawings used for analysis.
• Stormwater network:
• Stormwater network using HDPE pipes, curb inlets, head walls, and grassy
swales.
• EPA SWMM:
• Rainfall from NOAA (same storm as rational method: 10-yr 30 min)
• Infiltration using G-A
• Same peak flow geometry as rational method
• Evaporation from NOAA
• Compared pre- and post- developed conditions at same discharge
point.

9. Soil and
Rainfall
information
Clay sand, hydrologic group D
G-A parameters
from Table 4-7 of
SWMM manual
Suction head:
9.41 inches
Hydraulic
conductivity:
0.02
NOAA rainfall for 10-yr 30-min:
1.91 inches

10. EPA SWMM pre- and post- developed maps

11. Results

12. 17.01
9.47
36.67
39.42
0
5
10
15
20
25
30
35
40
45
RATIONAL METHOD EPA SWMM
PEAKDISCHARGE(CFS) Peak Discharge for Pre- and Post-Developed Conditions
using the Rational Method and EPA SWMM
Pre-development Post-development

13. 31,019
18,362
61,169
65,872
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
RATIONAL METHOD EPA SWMM
VOLUME(CF) Total Volume of Discharge for Pre- and Post-Developed
Conditions using the Rational Method and EPA SWMM
Pre-development Post-development

14. Sources (will integrate citations into
presentation)
• Expert System for Calibrating Swmm C. Baffaut and J. W.
Delleur, Member, ASCE
• Automatic Calibration of the U.S. EPA SWMM Model for a Large
Urban Catchment Janet Barco; Kenneth M. Wong; and Michael K.
Stenstrom, F.ASCE