Department of Marine and Coastal Resources [1] concluded causes of coastal erosion in Thailand as follows:
1) Inappropriate usage of coastal areas: this includes seashore poaching, infrastructure developments, mangrove forest deforestations. Seashore poaching structures such as villas and bungalows directly affect circulations of currents in their areas and usually block the longshore sediments transport. Infrastructures constructed in coastal areas, for example, seaside roads, were sometimes constructed on dunes or swash zones and affected coastal morphodynamic processes. Mangrove deforestations devastate natural coastal barriers and cause coastal erosion. In Thailand, many mangrove forests were deforested to produce charcoals and to construct shrimp farms.
2) Lack of sediments: naturally: coastal sediments come from the weathering of sedimentary rocks. These sediments transport through rivers and river mouths. Some structures, such as a dam, can block riverine sediments and result in coastal erosion.
3) Development of coastal projects: big projects such as industrial estates and ports constructed in coastal areas may have substantial effects to coastal process in their adjacent areas. Frequently, heavy depositions of sediments occur in upstream sides of the projects, and heavy erosion occurs in downstream sides of the projects.
4) Natural coastal processes: coastal erosion can be naturally caused by the effects of natural forces, which including the waves force, the current force, the tidal force, and the wind force. In Thailand, waves tend to be higher in the lower south part, where is an open area. Thus, when a typhoon hits Thailand, damage on the lower south coasts tend to be higher than the others.
5) Lack of databases: a database is one of the essential tools for planning coastal projects; data—such as wave records, historical bathymetries, historical shorelines, and typhoon or storm surge records—is used for planning and investigating coastal projects. However, in Thailand, there are only a few wave observations stations. Moreover, production frequencies of bathymetry maps, aerial photographs, and satellite images is low. Lack of database affects the accuracy of simulations and the evaluation of projects.
Reference
[1] Department of Marine and Coastal Resources. “Strategies for Managing and Solving Coastal Erosion Problems,” ISBN 978-974-286-451-4, available online at https://www.dmcr.go.th/detailLib/272 (in Thai)