Beach Rotation

Beach rotation is the cyclic redistribution of sand along an embayed beach so that one end accretes while the other erodes, then reverses. It is driven by shifts in the dominant wave direction, which change the longshore current and littoral drift along the embayment. On a pocket beach bounded by headlands the planform pivots about a central node, hence rotation. Multi-year wave-climate cycles such as the El Nino-Southern Oscillation force the alternation on many Pacific and Australian coasts. Rotation complicates erosion management because a single end can lose sand without any net change in the embayment’s total volume.