The Role of Geotextile Tube as Low-Crested Breakwaters in Restoring Severe Beach Erosion Problem at Pebuahan Beach in Bali Island

Abstract

Pebuahan Beach in Jembrana Regency, Bali has experienced severe beach erosion since the construction of the Nusantara Pengambengan fishing port, 10 km east of Pebuahan. Efforts to countermeasure the coastal problem has been carried out by many local residents, but failed due to strong longshore drift. Through a collaboration between the Research Center for Water Resources, the Bali Penida River Basin, and PT. Geotechnical Systemindo, the implementation of low-crested breakwaters (LCB) or PEGAR, made of Woven Geotextile Tubes was initiated. Four woven geotextile tubes C12.9 m with length varied from 20 m to 25 m were installed to form LCB with the length of 60 m, at distance to the coast of 50 m. The monitoring of shoreline changes was conducted over the 3 months after its installation, which shows the formation of a new shoreline with the amount of deposited sand of 185.8 m3. The breaking wave on LCB crest results in successfully controlling the longshore current, hence the longshore drift settles behind the LCB to form a new coastline. It is expected this field study can be treated as an additional input to improve LCB Guideline and to expand LCB effectiveness scope not only apply to shallow wave conditions and beaches such as on North coast of Java, but also can be applied more universally to a deeper coastal waters with high wave conditions.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/AFzvkvYY2Do

Environmental impact of submerged and emerged breakwaters

“…Substrate elevation was increased to a height appropriate for mangrove establishment. Sulaiman and Hidayat (2020) also noticed an alteration in the coastline that seemed to be eroded at both ends of low-crested breakwaters. Torres-Freyermuth et al.…”

“…Lately, submerged breakwaters have become more prevalent than emerged breakwaters ( Na’im et al., 2018 ). Since utilizing submerged breakwaters to prevent coastal erosion is more popular internationally, an issue has arisen whether they can protect beaches and enhance the environment ( Sulaiman and Hidayat, 2020 ; Torres-Freyermuth et al., 2019 ; Zanuttigh, 2007 ). Whether the environmental impacts of submerged breakwaters are well-understood is a major remaining question.…”

“… Pranzini et al. (2018) and Sulaiman and Hidayat (2020) found that low-crested breakwaters were relatively economical and affordable to the community, and they expected to apply low-crested breakwaters to not only shallow beaches, but also more universally to deeper coastal waters with harsher wave conditions. Furthermore, the construction costs can differ in different circumstances.…”

“… Sulaiman and Hidayat (2020) and Fitri et al. (2019) showed that submerged breakwaters significantly impacted beach realignment.…”

“…(2011) presented a similar study, in which a semi-submerged breakwater changed the alongshore sediment transport at Punta Marina, north-eastern Italy. Sulaiman and Hidayat (2020) found that low-crested structures created a rotary water current pattern, slowing down the longshore current velocity and causing rapid sediment deposition behind the submerged breakwater. The breakwater acted as a sedimentary trap, allowing the external water current to carry the sediment through the gaps during high tide and flow out during low tide.…”