Grade Stabilization Requirements for Incised Channels

摘要

The erosive process of channel incision completely transforms stable streams into channels characterized by degrading inverts, mass failing banks, and excessive sediment transport capacity. Destructive consequences of channel incision range from failure of transportation infrastructure, to loss of productive lands, to decreased flood control capability due to deposition of eroded sediment and debris. Adverse environmental impacts are no less severe, as entire channel perimeters are eroded and in-stream habitat, as well as riparian vegetation, is destroyed. Unfortunately, channel incision is usually experienced as a basin-wide instability rather than a localized erosion problem. Therefore, a systems approach, or basin-wide approach, is needed to assess channel instability and formulate integrated erosion control solutions for incised channel systems. This paper presents the systems approach used by the Corps of Engineers Vicksburg District in the Demonstration Erosion Control (DEC) Project of the upper Yazoo River basin in north Mississippi. Project watersheds have been investigated with the systems approach methodology, which incorporates such tools as field investigations, geomorphic assessments and hydraulic models. From the systems analysis, hydraulic and geotechnical stability criteria were developed which served as the basis for the planning and design of stabilization features. This paper also presents the methods used to deploy required grade control structures within the incised channel systems. Methods for determining spacing of structures are discussed, along with design considerations for achieving desired structure performance and impact on the hydraulic regime of the channels.