Development Of Simple Stream Rehabilitation Techniques for Urban Watersheds
Abstract:Stream rehabilitation methods developed in rural watersheds were modified and applied to moderate and highly urban watersheds. Urbanization increases the impervious area in the watershed, constrains the stream corridor width, and in some instances, reroutes the channel in a manner that reduces its length. The method developed integrates the fundamentals of geomorphology, stream stability and the required level of service for flood conveyance to design solutions that are cost effective, reliable, and simple to design and construct. The method identifies reference reaches in the upper less developed and in lower developed portions of the watershed, uses the reference reaches and engineering methods to determine the appropriate bankfull channel geometry, and then determine the bankfull bench widths to achieve the channel entrenchment ratios required for stable channel. Where such entrainment ratios cannot be attained, the channel is stabilized by incorporating additional protection of bed and bank required using natural materials. One approach is to incorporate buried boulders to form the bankfull channel. The boulders on the stream bed are covered with bed gravel and soil that is natural to the creek. Logs may be used when the logs are perennially wetted. When boulders are buried in the banks, the bank is vegetated with trees being planted in the crevices between the boulders. The stream rehabilitation is also designed to help improve flood conveyance and flood protection. Increasing the entrenchment ratio helps improve flood conveyance. Stabilizing the banks by reducing their erosion helps reduce the risk of undermining and eroding the levees for flood protection.
Document Type: Research Article
Publication date: January 1, 2008
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