This study examines the vulnerability of paddy fields to Cidurian watershed in Renged Village, Binuang District, Serang Regency, Banten Province. Renged village was chosen as the location of the research area, because there are two factors in the economic condition of the population, the majority of which work as farmers and the geographical location of the research area is located downstream of the Cidurian watershed and 0-2% slope. The results of interviews with local communities flooding in the study area occurred every year in the rainy season, with the largest flood events in the last 20 years occurred in 1994, 2001, and 2013. Based on this, the rice fields in the study area are vulnerable to Cidurian watershed flooding. Vulnerability analysis of rice paddy fields in the study area with landforms and community perception approaches, for vulnerability assessment based on an indicator approach with coring methods and weighting scenarios. Flood hazard analysis based on parameters of depth, duration, and re-flood period.
The results of the analysis of the study area have landform units from the fluvial process consisting of: dead river flows, alluvial plains, flood plains, natural dykes, and fluvial terraces. The largest area of fluvial landform in the study area is the alluvial plain with an area of 351.83 ha, which is the result of the sedimentation process on a flat topography with alluvium material. These conditions can be identified that the study area is affected by flooding and inundation activities, because the alluvium material comes from the deposition results when floods and inundation occur.
The results of the interpolation map of the depth of the study area showed that the highest maximum flood depth occurred in 2001 which was 3.8 m, whereas in 1994 and 2013 it was 2.8 m. The results of the interpolation map of the flood duration of the study area showed that the longest flood duration occurred in 1994 which was 23 days, whereas the year 2001 which is 21 days and 2013 which is 19 days. The analysis results related to the return period of flood hazard can be identified as a 6 year flood. The results of the flood hazard map analysis in the study area were reviewed based on the area, areas with high hazard class area of 161.20 ha, areas with medium hazard class area of 189.70 ha, and areas with low hazard class area of 120.77 ha. Based on the spatial distribution in landforms, the results of the analysis showed that the hazard Flood areas of research with a high class category are found in the landform units of floodplains, dead river flows, and alluvial plains associated with irrigation channels. Flood hazards are in the medium category, found in some units of the flood plain and alluvial plain. Flood hazard with low category is found in the form of terrestrial fluvial terraces, natural embankments, and some alluvial plains. Based on land use areas with high to moderate flood hazard classes, most are found in land use namely rice fields.
Vulnerability assessment results are based on six scenarios, showing that the vulnerability index values between hazard weight scenarios, productivity, land area, and land distance from rivers have the same minimum and maximum index values of 0-0.86. The highest vulnerability index value is found in the same vulnerability scenario, which is 0-0.89. Based on the spatial distribution of landforms, there is a similarity that most of the high vulnerability classes are in paddy fields located on floodplains and near irrigation channels. These conditions indicate that the hazard variable has a high contribution to the level of vulnerability of rice paddy fields in the study area.
Presented by Siti Dahlia (Geoinfo Batch X) at the 3rd Annual Scientific Meeting of the Indonesian Disaster Experts Association (PIT IABI) at ITB Bandung 23-24 May 2016