LOW-CREST BREAKWATER DESIGN AND HYDRO-MORPHODYNAMIC MODELLING IN LEGONKULON DISTRICT, SUBANG REGENCY

• Main Author: Evan Fernando, Paskasius
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/68940
• Institution: Institut Teknologi Bandung

Indonesia is ranked second in the world as the country with the longest coastline with a value of 108,000 km. The long coastline is inhabited by up to 16.42 million people and makes coastal areas widely used as a source of livelihood. Indonesia’s geographical condition which located in the tropics and at the confluence of two oceans and two continents, makes coastal areas prone to extreme weather, extreme waves, and erosion. One of the areas in Indonesia that has experienced massive erosion is the northern part of Mayangan Village and Legonwetan Village, Legonkulon District, Subang Regency, West Java Province. The northern part of the two villages has experienced a coastline retreat since 2008 and continues until 2022. The retreat of the coastline has caused the loss of land area so that the production of the main commodity of rice and the population in the two villages are at the lowest rank compared to other villages in the Kecamatan legonkulon. Land rehabilitation and coastal protection in Mayangan Village and Legonwetan Village are very important so that the welfare and quality of life of the population increases. Hydrodynamics and morphodynamics modelling were carried out using XBeach software to determine the point of low-crest breakwater development plan, configuration and dimensions of low-crest breakwater, and model the increase in coastline due to the presence of low-crest breakwater. The low-crest breakwater construction was planned to be located at a distance of 450m from the existing beach with a total of four low-crest breakwaters, the distance between low-crest breakwater is 428m, and the length is 1380m. The peak elevation of low-crest breakwater is at +0.2233m from the Mean Sea Level (MSL) and was designed to use the main armor layer in the form of dolos, the secondary armor layer in the form of natural stone, and the core layer in the form of natural stone with a smaller size. The low-crest breakwater dimension calculation refers to the Shore Protection Manual (1984) Volume I & II and The Rock Manual (2007). Morphodynamic modelling with daily wave conditions and a simulation time of six months showed that the presence of low-crest breakwater could increase the coastline as far as 100m to the sea with a maximum sedimentation thickness of 25cm. Meanwhile, morphological modelling with extreme wave conditions of 50- years return period and three hours simulation time did not show any reduction in coastline. It can be said that the low-crest breakwater development plan in the north of Mayangan Village and Legonwetan Village could increase the coastline and rehabilitate the land that has been lost.