Author(s): Warit Charoenlerkthawin; Komkrit Bidorn; Somboon Otarawanna; Butsawan Bidorn

Linked Author(s): Butsawan Bidorn

Keywords: Remote sensing; Coastal structure; Land use change; Shoreline change; Sediment transport

Abstract: The Ban Khlong Wan (BKW) is one of the important coastlines for fishery and sightseeing activities in the middle Gulf of Thailand. However, the BKW sandy beach has been transformed into a muddy beach after the construction of an 800-m long fishery pier, a 700-m long breakwater, and 12 detached breakwaters since 2007. The construction of these coastal structures was reported to be the primary cause of the beach material transformation. This study investigated the major cause of beach material transformation using historical images during 1966–2021 and shoreline change analysis. The results indicate that the fishery pier has trapped the sandy sediment transporting alongshore. Consequently, the coastline downdrift the pier has lacked sandy sediment supply resulting in shoreline erosion. Based on land use analysis, the downdrift coastline did receive not only longshore sediment but also riverine sediment from Wan Channel. Remote sensing data reveals that the 1.5-km2 marsh and mangrove forest upstream of the canal was entirely converted into an aquacultural area during 1976–1995. Since the Wan Canal conveys fine riverine sediment to the sea, including mud from aquaculture waste, the beach material on the downdrift coast seemed to be dominated by the riverine sediment after the sandy longshore sediment had been blocked by the fishery pier. Because the twelve breakwaters constructed along the downdrift coastline performed the function of reducing wave energy and stabilizing the shoreline, the transformation of the sandy to the muddy coastline of the BKW coast was mainly induced by the change in coastal sediment budget due to the fishery pier and inland aquatic activities.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0948-cd

Year: 2023