No abstract

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.

This paper describes the removement works and corrosion investigation of the 200m long coastal observation pier at Ajigaura beach, which was composed of steel truss framework supported by steel piles. The pier was constructed in 1973 and extended in 1976. The pier was used for observation of waves, currents and beach deformation in surf zone and exposed to severe sea state for more than 20 years. Removement works were operated from the provisional pier constructed in parallel to the observation pier. The steel piles were extracted after being cut beneath the ground level since they were judged to be undurable for the entire extraction due to the corrosion at the splash zone. Corrosion investigation also confirmed the effectiveness of various rustproof techniques.

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.

Damages due to wave overtopping were investigated through a nationwide questionnaire distributed among regional construction bureaus and local governments. Wave overtopping in recent 7 years was found to be reported at more than 250 coasts facing open sea as well as inner bay. In addition to the tangible damages of flooding and destruction of coastal structures, wave overtopping also causes serious damages of salt invasion to land and traffic interruption, which were not included in conventional cost-benefit analysis. The relationship between the damage level and the strength of wave overtopping was investigated, revealing high correlation for coastal structure destruction and low for salt invasion.