Mapping flood risk zone (a case study: Gajah Wong Sub Watershed, Special Region of Yogyakarta)

Abstract

Gajah Wong Sub Watershed often experiences a flood incidence that has potentials to destroy and cause material loss so that needed an examination on a flood risk. This study’s objective is to map the level of a flood disaster risk zone and its spread in Gajah Wong Sub Watershed, Province of Special Region of Yogyakarta. The study’s method used weighing and scoring method with overlay analysis technique of flood risk parameter attribute data consisting of flood hazard, vulnerability and capacity using Geographic Information System (GIS). It complies with Disaster Prevention-National Agency Head’s Decree No. 02/2012 with modification. Each parameter is modified, weighing and scoring are used to gain values of attribute data. The results of study indicate that flood risk in Sub Watershed Gajah Wong consisted of 3 levels, namely, low level of flood risk having 440.86 ha (89.22%), medium level of flood risk having 157.81 ha (3.20%) and high level of flood risk having 374.25 ha (7.59%). Low level of flood risk widely dominated distribution to upstream zone covering sub-district of Pakem, sub-district of Ngemplak and sub-district of Ngaglik. Medium level of flood risk was distributed to some middle areas and downstream zone covering some sub-districts, such as part of Umbulharjo, part of Kota Gede and part of Banguntapan. While, high level of flood risk was spread in south part of Depok sub-district and north part of Pleret sub-district.