How much velocity information is necessary to predict sediment suspension in the surf zone?

Instantaneous horizontal water velocity, or velocity to a power, does not contain enough information to predict suspension in the surf zone. Unlike steady uniform flow, more one than one velocity is necessary to parameterize pick-up and mixing of sediment into the water column. Using a velocity history improves predictions of suspension by more carefully specifying flow conditions (including accelerations and changes in accelerations) responsible for suspension. Suspension in the future is better predicted than suspension at the same instant as velocity measurements. Incorporating such a lag between velocity and concentration improved predictions, with optimum lag time increasing with elevation above the sea bed. These lags are largely due to the time for an observed flow event to effect the bed and mix sediment upward.