Book Description

Sediment deposition occurs in the lower reaches of the concrete-lined Corte Madera Creek flood control channel because the elevation of the channel bottom is below sea level. These sediment deposits, combined with the presence of tube worms and barnacles on the channel walls, reduce the flood-carrying capacity of the channel. The upstream portion of the original flood control project was not completed and flood flows above 3,000 cfs are not contained in the natural channel upstream. Thus, there is reduced flow competency to carry the coarse sediment load delivered by flood flows. With annual maintenance and upstream containment of breakout flows, most of the sediment deposited in the concrete channel from seasonal antecedent flow can be washed out by the time the flood peak occurs. An HEC-6 numerical sedimentation model study was conducted to evaluate several alternative plans to provide flood containment and sediment storage while also maintaining the natural characteristics of the upstream channel.