Estimation of suspended sediment trapping ratio for channel infilling and bypassing

describes a method for estimating the percentage of sand-sized material placed in suspension by breaking waves and carried by a cross-channel current to either fall into a navigation channel or travel across it. Required inputs are channel width and depth, depth in the vicinity of the channel, depth-averaged current velocity perpendicular to the channel, and sediment fall speed. The procedure is applicable to inlet entrances that experience breaking waves. The percentage of material deposited into or passing a channel is an input to the channel infilling model described in Kraus and Larson (2001). CALCULATION METHOD: Navigation channels issuing from an inlet intercept sediment that is moving alongshore (Figure 1). The longshore transport may be generated by wave- and wind-generated currents, and by the longshore component of the flood-tidal current entering the channel. Sediment can pass over the channel by moving in suspension, and it can be deposited on the channel bottom and, possibly, resuspended and transported out of the channel (Kraus and Larson 2001). This Technical Note presents a method for estimating the percentage of suspended material transported alongshore (perpendicular to a channel) that will be deposited in a channel (the trapping ratio), from which the amount passing over the channel is determined.