| dc.description.abstract | Yogyakarta urban area is one of the urban cities in Indonesia which has rapidly development. It will grow and increase number of land use. Gajah Wong Sub Watershed is located in Yogyakarta urban area. According to data from BPBD (Badan Penanggulangan Bencana Daerah) of Yogyakarta City, Gajah Wong Riverbank (2015) had passed three times flood disaster on January, March and April. It has negative impacts, they are loss infrastructure, economic impact,
environmental degradation, and health problem. This research will identify this flood by using Geographic Information System (GIS) to analysis the impact of reduced water catchment areas, the influence of land slope towards the runoff flood, and mapping the flood prone
areas. The GIS application used are Quantum GIS (QGIS), ArcGIS and Integrated Land and Water Information System (ILWIS). Analysis of rainfall use three methods they are Gumbel, Log Pearson III and Log Normal. Distribution calculations performed using Hasper Rain-Weduwen method. The calculation of the concentration time using Kirpich method. Mononobe method is used to calculate rainfall per hour and Rational Method for runoff discharge. The results show that every 3% of landuse change will cause 1% runoff discharge. It is proven by the data of Tamanan, Banguntapan and Giwangan, Umbulharjo villages that show these areas have 15% landuse change and 5% of runoff discharge. The level of vulnerability flood runoff divided into 4 levels, they are very low, low, high and very high. The results of data processing indicate
there were 5 villages with flooding vulnerability runoff is as high as Caturtunggal, Demangan, Baciro and Warungboto. With an area of each respectively is 0.301 hectares, 37.621 hectares, 32.796 hectares, 33.115hectares and 0,313 hectares. The more flat the slope of the land, the more potential occurrence of inundation flood discharge runoff. The four villages have flat land
slope is equal to 0-2% of slope land. | en_US |
