DFHADprototype071409.. - Urban Drainage and Flood Control District
DFHADprototype071409.. - Urban Drainage and Flood Control District
DFHADprototype071409.. - Urban Drainage and Flood Control District
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SECTION 3 – HYDROLOGIC ANALYSIS<br />
HOFFMAN MAJOR DRAINAGEWAY PLANNING<br />
FLOOD HAZARD AREA DELINEATION<br />
Hydrographs for the 100-year event storm are shown on Chart B-3 in Appendix B at five (5) different<br />
locations along Hoffman <strong>Drainage</strong>way.<br />
3.6 COMPARISON WITH PREVIOUS STUDIES<br />
The flows from the EPA SW MM model were com pared with those supplied by FEMA as part of the FIS<br />
study. Upon examining the HEC-2 model that was provided as suppo rt for the FIS, it became apparent that<br />
there was a discrepancy between the flows in the model <strong>and</strong> those published in the FIS. For the purposes of<br />
this study, the HEC-2 model will be used for comparison, as it appears to have more reasonable flows.<br />
The current model was calibrated to the FEMA HEC-2 model by systema tically varying the subbasin width<br />
characteristic within EP A SWMM. The EPA SW MM model was compared to the HEC-2 m odel at two<br />
locations: East 88 th Avenue <strong>and</strong> Devonshire Road. The results of the calibration are shown below.<br />
TABLE 3-2<br />
Comparison of 100-Year Peak Flow to Other Studies<br />
Location FIS FEMA HEC-2 Moser – Calibrated b<br />
88th Avenue 680 (0.8 sq.mi.) 1000 a 1069 (0.8 sq.mi.)<br />
Devonshire Boulevard<br />
1240 (1.2<br />
sq.mi.)<br />
1220 a 1079 (0.9 sq.mi.)<br />
a Tributary area unknown<br />
b Calibration occurred before watershed area was exp<strong>and</strong>e<br />
3-3<br />
DFHAD Prototype