河川供給土砂量の減少に起因する湖浜変形 : 琵琶湖の鴨川と近江白浜の例

概要

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Lakeshore changes around the Kamo River mouth and Ohmi-shirahama Beach in Lake Biwa were investigated. River improvement was carried out in the Kamo River as a countermeasure against floods by excavating the riverbed to widen the river channel. After the river improvement, sand discharge from the river was significantly reduced and shoreline recession occurred around the river mouth, resulting in further beach erosion on downcoast beach, Ohmi-shirahama Beach. The shoreline changes were investigated by comparison of past aerial photographs and longshore sand transport was estimated from the shoreline changes. Past beach changes were reproduced and future beach changes were predicted using the contour-line-change model. Any measures disrupting continual sand transport from a river to the lakeshore cause lakeshore erosion, suggesting the importance of maintaining continual flow of sand from a river to lakeshore.
2011-10-25