RIASSUNTO
ABSTRACT
The research on the effect of coastal facilities for protecting an estuary from channel blockage and a coast from beach erosion by waves demands to understand wave propagation, nearshore current and sediment transportation. The purpose of this research is to study the effect of jetty and propose countermeasures to compensate insufficient safety in Chumphon estuary, Chumpon province. The field survey is executed, topographic maps, bathymetric data, wave data for storm surges, tidal data were collected and inputted in Ca's numerical model (Ca et. al., 2000). This model consists of the near shore fluid dynamic model based on the Boussinesq equation and the topographical change model which the bed load and the suspended load were considered. Although the jetties are very effective for channel maintenance, since diffraction waves by the jetties has drawn sand in the north-side beach of the jetties toward the jetties, serious coastal erosion has occurred in the center of this north-side beach. Moreover, according to the simulation results by using Ca's model, in the south-side beach of the jetties, if a typhoon of Linda classes hits this area, since heavy overtopping occurs, wave dissipation facilities are necessary.
INTRODUCTION
Many estuaries in Thailand have affected by the waves that result in the deposition of sediment increasing and closing maritime routes where are the connection between the river and the sea and making navigation problem. The local government has to find the way to prevent such problems and has to conduct dredging annually to maintain the depth and width properly so that the ship can normally access. A lot of budget are lost in dredging each year. Therefore, the jetties have been constructed to protect the wave and sediment deposition into the estuary and to maintain the depth and width of the channel and help the fishermen around the estuary can take their boats to catch fishes as usual.