FLOOD07072

• County: Statewide
• Stream Name: South Platte
• Basin: South Platte
• Title: Water and Related Land Resources Management Study Volume IIIC - Appendix A
• Date: 7/14/1980
• Prepared For: South Platte and Tributaries
• Prepared By: CWCB
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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Table 11
Land Use Vs. Percent of Impervious Area

Land Use

Percent Impervious

Industrial
Dense Residential
Normal Residential
Large Lot Residential
Open Areas

95
52
40
30
5

FLOOD ROUTING

The flood routing portion of the South Platte River model was

developed using the Missouri River Division diffusion routing

technique. This technique is based on the solution of two finite

difference equations that represent the continuity of flow and the

flow friction along any given stream reach. The computational

procedure requires a stage-conveyance relationship and a stage-

area flooded relationship for each selected channel and flood

plain cross section.

MODEL VERIFICATION

The flood routing portion of the South Platte model, and to a

lesser extent the inflow portion, were tested by routing the June

1965 and May 1973 flood events between South Platte River gaging

stations where inflow was gaged or could be estimated with acceptable

accuracy. Ungaged inflow hydro graphs were estimated using the inflow

portion of the South Platte model described on page 55. Other

factors affecting the flow between gaging stations, such as water

trapped in the overbank area and withdrawals for irrigation, were

not accounted for in the flood routing procedure. This resulted

in some of the reconstituted hydro graphs having more volume than the

actual event. The actual and reconstituted hydrographs developed for

the 1965 and 1973 floods are shown on plates 9 to 11 and 13 to 17.

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59