LAHAR FLOOD RISK ANALYSIS FOR SUPPORTING DETAILED SPATIAL PLANNINGAT THE CODE RIVER�S RIPARIAN ZONE IN YOGYAKARTA MUNICIPALITY

Lahar flood is the threaten disaster in several area in Yogyakarta municipality i.e. Code river and Gadjah Wong river. This disaster is aftermath disaster following the periodically eruption event of Merapi Volcano. Especially Code river, based on the last eruption in October 2010, lahar flood strucked settlement along this river in the end of 2010 and early 2011. The lahar flood height in several points of settlement area along the Code river was reached approximately 0,5 to 1,4 m (pre research survey 2012). In case of present Yogyakarta Municipality�s Spatial Planning, Code river has been predetermined 50 m buffer zone for preserve area. The map of buffer zone can be seen in the annexes of Yogyakarta Spatial Planning regulation number 2 year 2010 about Spatial Planning of Yogyakarta Municipality. The result on literature study and indepth interview with several local agencies indicate that this regulation was not included lahar flood analysis in the zonation process of preserve area yet. Conducted research on lahar flood risk analysis tries to propose method in zoning system improvement for supporting detailed spatial planning which should be compiled 3 years after the regulation above established. The four factors were analyzed i.e. hazard, vulnerability, capacity and amount. The risk calculation was done in two condition i.e. lahar flood event in 2011 and predicted impact after flood proofing activity. The improvement on zoning area of present Spatial Planning Regulation of Yogyakarta Municipality Nr. 2 year 2010 is on zone mapping method by enhancing techniques in data collection for element at risk , lahar flood event to be combined in lahar flood risk calculation together with demographic data for social vulnerability assesment and capacity calculation. Deliniation of the actual riparian zone is proposed to be considered as one option to define buffer zone for preserve area in Code River. The final information is generated by overlaying existing zone , two risk map and zonation of preserve area according to the latest regulation Government Regulation No. 38 year 2011 about River