Impact of Shoreline Change on the East Coast of Bengkalis Island

This study was conducted in October 2024 on Bengkalis Island, Riau, using a survey method. The determination of station points for analysis was based on shoreline change data processed from satellite imagery, covering the period from 2014 to 2024 for Bengkalis Island. The substrate consists of very fine muddy sand. Sediment analysis identified two types of sediment: sandy mud and mud. At Station 1, the sediment was predominantly sandy mud, with 50.25% mud and 32.15% sand; at Station 2, the sediment was 83.33% mud; and at Station 3, it was 76.35% mud. The topography of the area is lowland, with an average elevation ranging from 1 to 6.1 meters above sea level. The coastline is gently sloping, and the lowest tide extends quite far from the shore. Depth measurements in the observation area, which has a high erosion rate, range from 1.1 to 6.0 meters. Tidal analysis indicates a mixed tide type, predominantly semi-diurnal. In this type, wave heights between the first and second high tides, as well as between the first and second low tides, typically vary within a daily cycle. Satellite image analysis of the mangrove area on Bengkalis Island from 2019 to 2024 revealed a mangrove area of about 43,000 hectares in 2019, which decreased to approximately 41,304 hectares in 2024, resulting in a loss of about 1,696 hectares over five years. Over the past 26 years, Bengkalis has experienced an average erosion rate of 59 hectares per year and an accretion (sedimentation) rate of 16.5 hectares per year. Some impacts of erosion include the loss of fish gathering areas, the reduction of beach width leading to land narrowing, damage to coastal infrastructure, and the destruction of mangrove forests due to land narrowing and deforestation.