Indonesia is a country that often experiences disasters. It is said often, because there have been 1,853 disasters in 2016. This is more than in the previous year as in 2012 there were 1,811 disasters, in 2013 there were 1,674 and in 2015 there were 1,732 disasters. According to data compiled by the Information and Public Relations Data Center of the National Disaster Management Agency (BNPB), there were recorded 654 disaster events at the beginning of 2017. Based on these data it is necessary to have basic data in each region in Indonesia that can spatially show flood-prone areas so that solutions can be found to minimize the impact of flooding as flood disaster mitigation. The right solution and serious efforts in handling flood problems will certainly increase the sense of security in the community both in flooded areas and those that have the potential and are affected by floods. The solutions that have been taken so far are more focused on post-flood control techniques, so they are not effective for prevention efforts. Prevention efforts can be carried out through continuous monitoring of vulnerable areas. One effort to facilitate monitoring of flooding in an area is through the provision of information on flood-prone levels. Information on the level and class of flood-prone areas can be realized by making flood hazard maps. Pontianak City is the capital of West Kalimantan Province, with an area of 107.82 km2, located at 00 02’ 24” North Latitude up to 00 05’ 37” South Latitude, and 1090 16’ 25” East Longitude up to 1090 23’ 01” East Longitude. The city of Pontianak is located in the lowlands with a height ranging from 0.10 meters to 1.50 meters above sea level (masl). The city of Pontianak is a tropical region with temperatures ranging from 22.4 0C - 36.4 0C, with high humidity.
This research was conducted to establish a vulerability model of flood hazard in the city of Pontianak, West Kalimantan Province based on GIS. The model was based on scoring and weighting of biophysical factors. The AHP (analysis Hierarchy Process) method and logical formulations were used to establish the model.
The result showed that the accuracy of model by AHP to determine the vulnerability of flood was only 80% in Pontianak City. Therefore the model was not good enough to represent actual condition in the field. The accuracy of model using logical formulations to determine the vulnerability level of flood was 84%, this means that the results of model 1 have a confidence level of 84% after checking the location of inundation points on the map against inundation points in the field. The Kappa accuracy value in model 1 is 79.3%, this means it is able to avoid 79.3% errors.
The model of flood vulnerability (model 1) explains that most of Pontianak City has a very high level of flood vulnerability, which is 31,440,568.8 m2 or 29.11% of the total research area of 108,003,319.8 m2. The vulnerable area is 29,945,485.7 m2 or 27.73% and the less secure area is 22,126,936.3 m2 or 20.49% and the safe area is 24,490,328.7 m2 or 22.67% of the total area.Subdistricts that have the most area in a very flood prone area in a row are City Pontianak Sub-District covering 8,299,516.9 m2; then followed by South Pontianak Subdistrict covering an area of 6,980,141.8 m2; West Pontianak Subdistrict covering an area of 5,638,021.4 m2; North Pontianak District covering an area of 4,095,410.0 m2; Southeast Pontianak Subdistrict covering 3,830,011.8 m2; and the District of East Pontianak covering 2,597,441.2 m2