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 4 – HYDRAULIC ANALYSIS<br />
HOFFMAN MAJOR DRAINAGEWAY PLANNING<br />
FLOOD HAZARD AREA DELINIATION<br />
The channel is undersized at the Lower Clear Creek Canal at grade crossing. This causes flows to split out<br />
of Hoffman <strong>Drainage</strong>way at this location <strong>and</strong> sheet flow overl<strong>and</strong> to the northeast. This is the reason for the<br />
shallow flooding region on the north side of 86 th Avenue, between Steele Street <strong>and</strong> the South Platte River.<br />
HEC-RAS analys is ind icates th at a num ber of struct ures do not contain the various storm events. The<br />
results of the analysis are shown in Table 4-1<br />
TABLE 4-1<br />
Structure Hydraulic Analysis<br />
(Structures Exceeding the Allowable Overtopping Criteria)<br />
Structure Station<br />
Return Event<br />
10-Year 50-Year 100-Year 500-Year<br />
88th Avenue Pipe 76+00 X X X X<br />
Rainbow Avenue Culvert 64+00 X X X X<br />
Old Welby Road Culvert 48+70<br />
Railroad Bridge 47+50<br />
Welby Road Culvert 46+25<br />
Steele Street 32+60<br />
X X X<br />
LCCC Crossing<br />
30+00 X X X<br />
Maintenance Road 8+25<br />
Maintenance Road 2+75<br />
Pedestrian Trail 2+00 N/A - Overtopped by S. Platte River Backwater<br />
X = Storm Event Peak Flow Exceeds the allowable overtopping criteria<br />
Additional details in Appendix D<br />
4-3<br />
DFHAD Prototype
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