Channel Stability
This summary presents natural channel design concepts, and potential benefits and challenges of alternative drainage channel design.
Channel Form:
Natural channels almost always form two stages, a main "bankfull" channel and a floodplain. Flow and sediment interactions between these two stages largely determine channel condition and behavior. Historically, channel design for drainage improvement has not incorporated the functional benefits of a two-stage channel.
Stable channels maintain a dimension, pattern, and profile such that they neither aggrade nor degrade.
Bankfull Discharge and Channel Dimension
The exact form of a stable channel reflects local conditions. Modified channels tend to be unstable because they have been widened, deepened, or reduced to a single stage relative to stable channels in the same locality. Over-deepened channels are prone to erosion and meander development by lateral erosion. Over-widened channels are prone to aggradation and alternate bar formation. If allowed, unstable channels will evolve to form a stable dimension, pattern and profile.