Abstract:
This paper presents case studies with two-stage channel geometries that were sized based on geomorphic principles. Geomorphic data were collected at the project site and throughout the watershed. Watershed specific regional curves were developed for each project. Factors considered in sizing each system were the widths and depths of the inset channels that were associated with the channel forming discharge, bench widths, and the side slopes of the banks of the second stage. The channel-forming discharges for the inset channels corresponded with appropriate recurrence intervals for the region. The approach leaves the preconstruction inset channel intact and constructs, or widens, benches at elevations consistent with channel-forming and regional curve concepts. Two-stage channel system construction was discovered to be easier than clean out operations for traditional trapezoidal channel maintenance. Overall, two-stage channel projects cost more than traditional channel maintenance, but they have an anticipated improved design life. Since construction, cross-section surveys were periodically made for two case studies. No elevation changes were found in the benches, but the inset channels have narrowed.
Footnotes
George E. Powell is an engineer with Brockway Engineering in Twin Falls, Idaho. Andrew D. Ward is a professor in the Department of Food, Agricultural and Biological Engineering at the Ohio State University in Columbus, Ohio. Daniel E. Mecklenburg is an ecological engineer for the Soil and Water Conservation Division of the Ohio Department of Natural Resources in Columbus, Ohio. Joe Draper is a program director at the Nature Conservancy in Angola, Indiana. William Word is the Hillsdale County drain commissioner in Hillsdale, Michigan.
- Copyright 2007 by the Soil and Water Conservation Society
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