No abstract

Intangible effects due to coastal disasters were investigated on the basis of questionnaire distributed among coastal residents. Sampled people who have not experienced coastal disasters tended to feel more fear and uneasiness against coastal disasters. Those who experienced coastal disasters generally feel fear and uneasiness at the occurrence of the disaster and during evacuation. Disconfort gradually tends to dominate in the recovery stage. Further analysis revealed that the intangible effects due to coastal disasters were classified into three patterns depending on the amount of tangible damages. A questionnaire sheet was presented, which will be used to estimate the intangible damages in monetary term based on the Contingent Valuation Method.

The benefit of beach preservation at Niigata coast was estimated by the Contingent Valuation Method. Estimation was performed from the environmental aspect on the beach recovery efforts of Niigata coast by shore protection works. The result was correlated with various properties, such as age, sex, annual income and the distance of the residence from the coast. It was found that median value of 1,591 yen/year can be afforded for the maintenance of the present beach environment for the use of recreational purposes. High correlation was found between the interest on beach preservation and the frequency of visit to the beach.

Beach changes triggered by the construction of detached breakwaters and harbor breakwaters were investigated through comparison of aerial photographs on the Yotsukura and Natsui coasts both located in a pocket beach of 11km long stretch facing the Pacific Ocean. Formation of wave calm zone behind these breakwaters induced severe beach erosion on the surrounding beaches as well as sand accumulation in the lee side of the structures. Further the construction of gently-sloping coastal revetment covered vast area of natural sandy beaches. Deep concern should be paid to the change in this coastal situation in order to preserve and recover natural coastal environment. key words: Beach erosion, gently-sloping coastal revetment, aerial photograph field observation

The effect of the beach nourishment on the Yamamoto coast which has been suffering from serious beach erosion was evaluated. From the fluorescent sand survey, even medium sand with diameter of about 0.3mm passed over the headland in coming of significant waves higher than 2m. About 80% of sand particles moved out from the injection point within 1 year. According to the Bruun equation, the profile of this beach was identified as the concave and eroded type. Sediment survey showed that sand particles larger than 0.25mm stayed in shallow area with depth less than 2m and remained there for more than 1 year. In addition, Numerical model built to estimate the effectiveness of different grain size on beach nourishment demonstrated availability of gravels for effective nourishment.