Spatial Modeling of Coastal Flood Due To The Fishpond To Tidal Waves in Bengkalis, Indonesia

Bengkalis Island is one of the small islands in Riau Province which is located on the east coast of Sumatra which is separated from the island of Sumatra and is in the middle of the Malacca Strait which is directly facing the ocean which is feared that some coastal areas will be affected by the large ener- gy of the tidal waves that propagate on the land surface. Make coastal areas in- undated by tidal floods. This is exacerbated by the conversion of mangrove land into Fishponds, which is carried out en masse to support the economy of the Bengkalis community. even though this is very vulnerable to the large energy of sea water waves which easily inundate coastal areas due to energy reduction in mangrove land cover. Along with the degradation of mangrove land, it is also exacerbated by global warming which causes sea air to rise. it is very vulnera- ble to coastal areas, especially in the research area. This research method uses geospatial modeling, using tidal data from the geospatial information agency (BIG), land cover image classification, soil surface roughness index, and flood scenarios. The results of this study we found that many coastal areas are prone to tidal flooding. At various maximum heights there are variations in the distri- bution of tidal flooding, for the final decision we use the worst scenario using the highest tidal discharge, which is 3.4 meters. This simulation model inundat- ed more than 74% of use in coastal areas, not only that, many agricultural areas were also affected by this tidal flood. We developed this simulation for analysis of losses due to the tidal wave, we found a loss index that reached 62% of the total loss of residential areas, including the loss of infrastructure and residential buildings.