FLOOD06573

• County: Boulder
• County: Weld
• Community: Boulder, Weld Counties
• Stream Name: Coal Creek, Rock Creek
• Basin: South Platte
• Title: Flood Hazard Analyses Coal Creek and Rock Creek, Boulder and Weld Counties
• Date: 8/1/1976
• Prepared For: Boulder County / Weld County
• Prepared By: USDA Soil Conservation Service
• Floodplain - Doc Type: Floodplain Report/Masterplan

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APPENDIX II

A 1 imited number of copies of this appendix has been. produced
for planners, engineers, developers, and others concerned with the
development of Coal Creek and Rock Creek flood plains, It was prepared

by the U. S. Department of Agriculture, Soil Conservation Service,

1n cooperation with the Colorado Water Conservation Board, the Urban

Dral~age and Flood Control District, Boulder and Weld Counties.

Included are computations for a theoretical floodway capable

of carrying the IDD-year frequency discharge at an increase in rise

In water surface elevation above the pre-floodway water surface elevation.

Data are in computer printout form and include floodway widths, cross

sectional flow area, and average velocities. Computations are for

an increase in rise of water surface in 0.5' increments from 0.0'

to 2.0' above the IDD-year flood. The theoretical floodway was computed

on the basis of equal conveyance reduction from each side of the flood

plain. The "Floodway widths - HUD 15 Computer Program," developed
by the Soil Conservation Service, is the methodology used for the
computat ions.

The data are keyed to the original cross sections and are compatible

for use with the water surface profiles, photomaps, and other exhibits

in the main report. The floodway stationing at each cross section

is from left to right when viewed in a downstream direction.