LONG-TERM VARIATION OF LONGSHORE SEDIMENT TRANSPORT

For planning and designing a new harbor located on the sand coast of Nouakchott, Mauretania, the Bijker formula was adopted to compute the longshore sediment transport. The shoreline is nearly straight at this site. The beach is composed of fine sand with a median grain diameter of D//5//0 equals 200 mu m. The beach slope is about 1:20. Wave observation data from 1976 to 1982 were used for the formula. Computed results show a clear variation of annual transport. The ratio maximum:mean value is 1. 31, and the ratio maximum:minimum is 1. 89 in seven years. Probability analysis indicates that the long-term variation of the longshore transport follows the Gumbel distribution. Accordingly, the formulae which can predict the probable and most disadvantageous total sediment transport values for multiple years blocked by a littoral barrier are derived.