With water flow, climate, and winds constantly shifting the coastal terrain from south to north, if there are dikes or other construction that clock the natural flow of water in the same direction this could cut off the shifting of the sand.
海岸的沙石隨著水流、氣候、風向南北移動，若有海堤或工程做往外海，阻擋水流自由的南來北往，也就切斷沙源的流動，學界將之稱為「突堤效應」。