This research aims to investigate the effect which big coastal facilities exert on coastal erosion due to waves in Khlong Wan Coast and examine some measures. Field surveys and a long-term simulation with the one-line numerical model indicated that the blockage of silt-and-sand supply from the northeast side of the coast by a big groin and the blockage of the supply from the southwest side by a huge detached breakwater has caused coastal erosion. Moreover, because the prediction using the one-line model showed that the beach in the southwest side of an old fishing port will become the most dangerous area, some measures for the coastal protection were proposed. Then, examinations on topographical changes of the beach, wave overtopping rates, etc. elucidate that sand nourishment is the most effective measure.
Nowadays, coastal erosion is an important issue in Thailand. Where connects Andaman Sea and Gulf of Thailand and consists of total shoreline length of 3,148.23 kilometers covering 23 provinces. Since many coasts in the Gulf of Thailand are suffering land disappearance that affect losses of economics, agriculture and so on, the Thai Government decided to construct countermeasures along these coasts. However, due to local characteristics of each coast such as wave characteristics, coastal structures, geological features, properties of silt-and-sand supply are different from each other. There is no all-round measure to stop all coastal erosion effectively. In order to protect these coasts from serious erosion effectively, it is necessary to study and analysis local characteristics of each coast, and provide suitable solution for each coast case by case.
The main causes of the coastal erosion result from human development. In Thailand, there are two types: felling mangrove woods that are natural wave dissipation facilities as introduced by Charusrojthanadech et al. (2013), and the case by side effect of big facilities such as a huge breakwater, reclaimed land and a jetty introduced by Doungpan et al. (2015).