FLOOD09931

• County: Statewide
• Community: Urbanizing Areas of Colorado
• Basin: Statewide
• Title: A Guide for Erosion & Sediment Control in Urbanizing Areas of Colorado
• Date: 1/1/1973
• Prepared For: State of Colorado
• Prepared By: USDA Soil Conservation Service
• Floodplain - Doc Type: Educational/Technical/Reference Information

Structure Selection

Stability of Grades Below Spillways

Generally, the degree of control or protection and the
size of the watershed are the primary considerations in
structure selection. The structure selection diagram,
Figure 15, is useful in determining the type of structure
needed.

The outlet of a spillway should be so designed that its
function or stability will not be reduced by scour or
deposition in the exit channel.

This diagram is for average field conditions and is based
on the most economical structure for the given head and
discharge, provided the site will permit installation of
the structure. Site and foundation conditions, there-
fore, are important factors in selecting the type of struc-
ture.

The channel grade below the spillway should be stable
to prevent undercutting of the outlet toe wall or can-
tilever support. Grade stability should be determined
by comparing velocities for the design flow in the
downstream channel with the permissible velocities for
the soils and vegetation in the channel.

Figure 15 General guide to structure selection

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