Flood Vulnerability Mapping in Lamongan District, Indonesia, using Fuzzy Analytical Hierarchy Process - Natural Breaks

Lamongan is one of the districts in East Java Province, Indonesia, which is often hit by floods, as evidenced by the occurrence of floods yearly. The occurrence of floods in Lamongan itself has an impact on hampering residents' activities and can cause material losses and other aspects such as health, economy, and the environment. Flood risk assessment studies are essential for identifying critical or high-risk zones. It is helpful as a flood disaster preparedness and decision support system for the government and the community. This research proposes flood vulnerability mapping in Lamongan based on multi-criteria using the Fuzzy Analytical Hierarchy Process (FAHP) – Natural Breaks method. The multi-criteria used consisted of population density, availability of pumps, Bengawan Solo river level, elevation, history of flooding, and rainfall. The weight of the FAHP results will be classified using a natural breaks algorithm, producing a low, medium, and high flood susceptibility index in 27 sub-districts. This system is built on a mobile device to display the vulnerability map spatially. Based on the GVF calculation, the FAHP-Natural breaks of 0.75 have a better priority and grouping value than the AHP-Natural breaks of 0.69.