Abrasion of Coast Composed of Loose Material

Abrasion of coasts is considered, the destruction of which is accompanied by extraction of sediments capable of forming a beach (sand, gravel, pebble). The behavior of such a type of coast is controlled by the feedback between the abrasion rate and volume of growing beach. The suggested evolutionary model leads to conclusion that abrasion should decay exponentially with time. The duration of the process may be measured in decades, centuries, or millennia depending on the fraction of beach-forming material incoming from the cliff. A rise in relative sea level contributes to an increased duration of abrasion. To predict the yearly volume of cliff abrasion, the approach by Larson et al. [15] is applied, taking into account the difference between the elevation of the beach and height of wave runup. The computational formula includes an empirical coefficient, which is estimated from data on the coasts of the Kama water-storage basin and Sea of Okhotsk (where the tide plays a significant role in cliff abrasion). It is shown that a comparatively small-scale beach fosters a substantial decrease in the abrasion volume. Abrasion of a submerged coastal slope is determined by both the cliff abrasion rate and "closure depth" concept.