Impact of coastal development on coastal morphology of Taiwan: Case studies and proposed countermeasures

Abstract

When economic expansion started in the late 1970s, Taiwan was in desperate need of better infrastructure. In response, the government began construction along the coasts around the island. Many of these structures were constructed under time constraints, and their possible effects on the environment were not considered. Years later, some of the structures were found to have disrupted littoral sediment transport, resulting in the retreat of shorelines downstream. The Integrated Coastal Zone Management Plan demands the implementation of remedial measures for erosion by the responsible party in the near future. However, as morphological changes are complicated processes involving both natural and human-induced drivers, the liabilities of the parties involved are typically difficult to determine. In this study, bathymetric analysis and numerical simulation were used to assess the effects of coastal structures on coastal erosion. With the former, the rate of change of the bathymetric volume along the shore was used to identify the extent of the structural effect. The latter one is then used to clarify the respective effect of adjacent structures on coastal bathymetry. Three cases with different surroundings were considered to verify the scheme. It is suggested that range of influence of the structure should be determined in terms of coastal cells. In the case of multiple structures existing within a cell, the cost of remedial measures should be proportional to the length of the structure vertical to the coastline. Remedies to restore the continuity of longshore drift are then proposed. These results can be used to promote effective coastal zone management and prevent further deterioration.