Coastal erosion in the north-eastern sakhalin island
https://doi.org/10.7868/S043542811804003X
Abstract
Based on the GIS processing of aerial (1952, 1974) and satellite (2014, 2015) images and subsequent analysis of the spectral density graphs of erosion intensity, erosion rates were assessed on the shores of north-eastern Sakhalin. Spatial pattern of coastal erosion demonstrated rhythmic regularities. The erosion rhythms with a wavelength of 1.3, 2.0, 4.0, 5.6, 8.5, 11.6, 25.6, 64 km were established. Average erosion rates nowhere exceed 2 m per year. Maximum erosion rates were noted in the shores occupied by high (14–28 m) Pleistocene terraces. For these areas, typical sediment supply due to the bank erosion was estimated at 5.6–7.7 m3 per 1 m of a coastline per year. The longest (wavelength 30–60 km) rhythms of erosion rate on the aligned shores of north-eastern Sakhalin are associated with stable zones of divergence of sediment flows characterized by a reduced volume of beach sediments. The erosion rhythm with the wavelength of 1.3 km corresponds to the dimension of the large megacusp structures of the beaches. Long-term studies of the structure and morphometry of the beaches allowed to do a conclusion about the formation of a completely wave-reducing profile on sandy-gravel beaches with the volume of deposits of 70–90 m3 per 1 meter of the extension of the shore. On the most of the aggrading shores there is no deficit of sediment, but erosion is observed even at the average values of the volume of beach sediments of 140–150 m3/m. As was shown on the example of three study sites with significant sediment reserves on the upper elements of the shore profile, the erosion of such shores is caused by the uneven distribution of beach material along the coast as a result of the formation of megacusps and their systems.
About the Authors
V. V. Afanasev
Institute of Marine Geology and Geophysics, FEB RAS, Yuzhno-Sakhalinsk
Russian Federation
Russian Federation
A. V. Uba
Institute of Marine Geology and Geophysics, FEB RAS, Yuzhno-Sakhalinsk
Russian Federation
Russian Federation
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For citations:
Afanasev V.V., Uba A.V. Coastal erosion in the north-eastern sakhalin island. Geomorfologiya. 2018;(4):26-37. (In Russ.) https://doi.org/10.7868/S043542811804003X
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