The effect of sea cliffs on inland encroachment of aeolian sand

The effect of sea cliffs on aeolian sand encroachment inland was monitored by means of traps measuring the sand transport and microanemometers measuring wind flow, because these are affected by the topography of the cliffs. Measurements were carried out on two cliffs in the southern coastal-plain of Israel: one 160 m and the second 240 m long, with front slope inclination of 30° to 40° and a height of 22-25 m. Results show that sand is incapable of climbing even moderate cliff slopes of 10°-15° because storm wind impinges on the cliffs at angles of 45° to 50° to the rim of the cliffs and is diverted to flow in a helical pattern parallel to the shoreline along the front slope of the cliffs. The diverted sand-moving wind is again deflected at the northern end of the cliffs, where its magnitude abates and it thus deposits sand that is being carried along the beach. The flow of the wind on the beach parallel to the foot of the cliff represents the effect of a non-homogeneous secondary wind. The wind is accelerated along the cliff, and as a result sand transport increases along the cliff. After a length of 150-200 m along the front slopes of the cliffs a state of equilibrium is achieved.