This course presents an alternative method of design for the conventional trapezoidal drainage channel. This two-stage channel system incorporates benches that function as flood plains and attempts to restore or create some natural alluvial channel processes. However, these two-stage channels are not an exact copy of natural streams, as the width of the benches is often small due to the confining geometry of the constructed channel.

This course outlines measurement and analysis procedures that can be used to size two-stage channel systems that are more self-sustaining than conventional one-stage constructed channels. Although the focus is primarily on an alternative design for constructed ditches, the technique may also have application in natural streams that have undergone incision or in streams where boundary constraints restrict restoration designs such as in urban or developed areas. 

Topics:

• Introduction and Background on Two-stage Channels
• Advantages and Design Procedures
• Conducting Field Measurements
• Bankfull Channel Design
• Flood Plain Channel Design
• Flood Conveyance
• Spreadsheet Tools

 Publication Source: USDA NRCS