海岸構造物による海岸侵食とその制御(3)-安定海浜工法による海岸侵食制御の方法論と安定海浜の形成に関する実験-

Abstract

In the third report, based on the numerical results of large scale coastal behavior and methodology for stabilization of Joestu-Ogata coast, a practical methodology for beach erosion control by headlands is first proposed. The practical application is proposed for stabilizing Joetsu-Ogata coast by formation of a series of stable sandy beaches.Secondly, experiments on the formation of stable sandy beach were carried out to examine the applicability of the proposed methodology for beach erosion control by headlands. In order to compare the hydraulic performances of the methodology for beach erosion control by headlands with other methods such as detached breakwaters in the stabilization of the sandy beach which is being eroded, by use of the similitude of beach change by Ito and Tsuchiya, the physical scales of the model experiment was determined, a series of experiments of the formation of stable sandy beach and beach changes by the methods were then conducted. The changes in shoreline and bottom topography after employing these methods for beach erosion control were observed and compared to find which method can stabilize the sandy beach in a long term sense. In the case of detached breakwaters, tombolos are generally formed in relation to the length of the breakwater and its onshore distance from the shoreline, but a couple of detached breakwaters spaced considerably are needed as headlands to stabilize the sandy beach. In the case of headlands, however, when a comparative condition in formation of sandy beaches by headlands is made, a stable sandy beach can be formed well between the headlands.