PERFORMANCE EVALUATION AND MONITORING LOW-CRESTED BREAKWATERS AS MITIGATIONS FOR COASTAL EROTIONS PROBLEMS

• Main Author: Rizki Saleh, Muhammad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/71327
• Institution: Institut Teknologi Bandung

Low-Crested Breakwater structures (PEGAR) have been proven in several previous studies as an option for coastal protection structures that are considered effective and environmentally friendly. During its operation, it is important to carry out further studies to review its effectiveness in terms of reducing incoming wave energy or in general as a shoreline stabilizer from erosion conditions. In this research, performance evaluation of PEGAR structures was carried out through 3 (three) approach methods including monitoring surveys, longshore sediment transport (LST) calculations and monitoring based on geographic information systems (GIS). The research location is in the Sukaria beach, Batang Regency, Central Java. In terms of location criteria, the PEGAR structures with the geotube model has been installed at the research location since 2019 by the Ministry of PUPR. Based on monitoring survey results, it found that the condition of PEGAR structures in 2022 has decreased functionally. This is because the structures undergoes a settlement process every year. Furthermore, based on the results of cross section measurements in the area behind PEGAR, it was found that after installation until conditions in 2022 tend to show an increase in sediment thickness elevation which indicates that the area behind PEGAR is experiencing sedimentation. Besides that, formation of the area behind PEGAR is also influenced by differences in seasonal conditions that take place in the coastal area. During the west monsoon the area behind PEGAR tends to have sedimentation while erosion occurs during the east monsoon. If considering LST conditions, the results show that PEGAR performance is most effective during the west monsoon and its effectiveness decreases during the east monsoon. The effectiveness of PEGAR performance based on monitoring shoreline changes for conditions before and after installation, the results show that before installation, the beach area tends to have erosion with an erosion rate of 3.52 m/year with a shoreline retreat of 12.96 m in 2015 – 2019, while conditions after installation show the trend of accretion at a rate of 5.97 m/year with a shoreline advance of 18.17 m in 2019 - 2022. The accretion trend obtained shows that as a shoreline stabilizer, the PEGAR structure has a positive performance.