T345 Tectonics, Geohazards, and Morphodynamics from High-Resolution Topography and Imagery

Wednesday, 25 October 2017
1:30 PM - 5:30 PM
Tahoma 4

THE SEDIMENT BUDGET OF CLIFF-DOMINATED BEACHES IN THE EASTERN MEDITERRANNEAN AT SINGLE-STORM TO SEASONAL TIME SCALES

Paper number: T345-3
Program: Technical Sessions
Time: 2:05 PM – 2:20 PM

Authors

Abstract

Quantifying sediment dynamics along cliffed coasts is a key step to better understand the geomorphic processes governing such environments. Here, we used data from 20 repeat terrestrial laser scanner (TLS) campaigns conducted over a three year interval (2013-2016) to quantify erosion and deposition at two cliffed beach sections along Israel’s Mediterranean coast. This study interval captured 14 individual winter storms. The two ~180 m long sites, ‘Neurim’ and ‘Gaash’, are 16 km apart. Both present an actively retreating eolianite cliff behind sand and gravel dominated beaches that separate the cliff-base from the water line. The Neurim cliff and beach are 25 m high and 40 m wide, respectively; at Gaash they are 40 m high and 10 m wide, respectively. Our measurements show that individual winter storms at both sites can result in either net erosion or deposition of several hundred m3 of beach sediments. Whereas erosion/deposition volumes and locations during individual storms do not appear to be correlated, both sites reveal an overall recurring pattern of fall-winter beach erosion and spring-summer sediment accumulation (‘replenishment’). The volumes of these seasonal-scale fluxes reached values of up to ~1100 m3. The total measured sediment influx during the three year interval for the Neurim and Gaash beaches exceeded the outflow and amounted to ~1000 and 800 m3, respectively. Wave scouring of cliff-collapsed material at both sites amounted to ~twice the volume of accumulated beach sediments. These measured fluxes indicate effective removal of ~50% of cliff-collapsed material from the shore platform within a time scale of several years regardless of beach width. Our measurements indicate a dynamic equilibrium for the sediment budget along the examined cliffed beaches and suggest that wave activity controls the net flux of sediment while cliff erosion and retreat are primary contributors to this equilibrium.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-297567

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