FLOOD05793

• County: Boulder
• Community: Longmont
• Stream Name: Dry Creek
• Basin: South Platte
• Title: Technical Addendum Floodplain Information and Flood Control and Drainage Plan
• Date: 4/1/1980
• Prepared For: Boulder County
• Prepared By: Water Resource Consultants
• Floodplain - Doc Type: Floodplain Report/Masterplan

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of the water surface profile proceed, in steps, from one cross section to

the next. The HEC-2 program is also capable of handling the effect of the

various hydraulic structures, such as bridges and culverts, which restrict

the flow.

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Additional detailed hydraulic calculations were made at road crossings

where the drainage structure capacity was small in comparison to the

flow over the road. Hand calculations were also required along Florida

Avenue where drainage structures are closely spaced and the water surface

profile is rapidly varied.

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The results of the flood computations are presented in Table-5. Figure-3

shows an index map for the flooded area plates. Flooded areas from a 100-year

frequency flood are presented on Plates through 10. The flood profiles are

shown on Plates II through 20. Plates 21,and 22 show a number of typical

cross sections of the stream and valley in the study area.

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The water surface elevations presented in Table-S are based on

computations which assume no reduction in the bridge conveyance capabilities

due to debris. Water surface elevations may increase if significant debris

blockage should occur.

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