Alluvial channel design techniques are generally used for movable boundary systems and streams with beds and banks made of unconsolidated sediment particles. In an alluvial channel, there is a continual exchange of the channel boundary material with the flow. Therefore, the design of an alluvial channel as part of a restoration project requires an assessment of sediment continuity and channel performance for a range of flows.

A wide variety of sources and techniques are available to the designer for designing stable alluvial channels. This course provides an overview and discussion of some of the most common alluvial channel design techniques. The use and application of regime, analogy, hydraulic geometry, and analytical methods are presented and described.

The channel geometry and flow conditions in an alluvial stream are interrelated. The river’s shape and size are determined by the river itself through the processes of erosion, sediment transport, sedimentation, and resuspension. Alluvial rivers are free to adjust section, pattern, and profile in response to hydraulic changes. Alluvial streams flow through channels with bed and banks made of sediments transported by the stream under-current conditions. In alluvial streams, the independent variables that drive the hydraulic design of the channel are discharge, sediment inflow, and bed and bank-material composition. The dependent or design variables are width, depth, slope, and planform.

Alluvial channel design approaches fall into five general categories: regime, analogy, hydraulic geometry, extremal, and analytical methods. Each method has its advantages and disadvantages, depending on the stream reach being restored.

Topics: Alluvial channel design variables Regime methods: Blench regime equations, Modified regime method Analogy method and reference reaches, Limitations of analogy method Hydraulic geometry method Procedure for developing hydraulic geometry relationships Generalized width predictors Hydraulic geometry for meandering sand-bed and gravel-bed rivers Uncertainty in hydraulic geometry relations Limitations of hydraulic geometry methods Constrained dependent variables Stable channel dimensions using analytical techniques Basic equations for sand-bed and gravel-bed streams Calculating sediment discharge and concentration Input requirements, Range of solutions, Sediment impact analysis Basic steps in alluvial channel design

Intended Audience: This course is intended for River, Geotechnical, Civil, Environmental, Water Resources, and other engineers whose job description requires an overview knowledge of alluvial channel design techniques and procedures.