Analysis of landslide hazard and risk in the upstream of Ciliwung Watershed and its relationship with spatial planning

Abstract

The upstream of Ciliwung watershed geomorphology was characterized by hills and mountains relief which were formed by volcanic processes. The steep slopes dominating the region and the high rate of human activities reflected by the dynamic land use change had turned the upstream of Ciliwung watershed region into landslide hazard area. Some landslide cases continue to occur in the rainy season every year, causing a lot of losses. This indicates that the mitigation of landslide hazard and risk by the government has not optimal yet. This study aims: (1) to analyze and map the landslide hazard in the upstream of Ciliwung watershed based on several estimation models, (2) to analyze and map the landslide risk area based on the level of landslide hazard, the society vulnerability, and the region capacity in the upstream of Ciliwung watershed, (3) to analyze the consistency of land use with spatial planning map, (4) to formulate the spatial plan/spatial arrangement guidance as an attempt to minimize the landslide disaster. The methods used in this study were spatial analysis, attribute analysis and descriptive analysis. Spatial and attribute analysis were conducted by utilizing geographic information systems (GIS) with the score and weight for each parameter, which is further classified into five classes, namely very low, low, moderate, high, and very high class. The higher the score and the weight, the higher the impact of the landslide cases, and vice versa. Spatial and attribute analysis included the mapping of landslide hazard, the mapping of vulnerability, the mapping of capacity, the mapping of landslide risk and the mapping of land use consistency. Descriptive analysis was performed to determine the relationship between spatial arrangement and landslide hazard, consistency level and landslide risk. The results of the study showed that the upstream of Ciliwung watershed has: (1) quite varied classes of landslide hazard, ranging from low to very high class, with the largest percentage is at the moderate class (54.89%); (2) very varied classes of society vulnerability, ranging from very low to very high class, dominated by the moderate class (53.25%); (3) high and very high region capacity classes; (4) the landslide risk classes which are spread almost evenly in very low class (39.75%), low class (32.02%), and moderate class (27.16%); (5) the land use of spatial plan is still at moderate to very high class of landslide risk and hazard; (6) the level of land use consistency toward spatial plan is still low (69.22%).

Geomorfologi DAS Ciliwung Hulu dicirikan dengan relief perbukitan dan pegunungan yang dibentuk oleh proses vulkanik. Lereng-lereng curam yang mendominasi wilayah iniserta tingginya tingkat aktivitas manusia yang tercermin dari perubahan penggunaan lahan yang dinamis, menyebabkan DAS Ciliwung Hulu menjadi daerah bahaya longsor. Beberapa kejadian longsor terus terjadi di musim penghujan di setiap tahunnya yang menimbulkan banyak kerugian. Hal ini menyiratkan bahwa penanggulangan bahaya dan risiko longsor dari pemerintah tampak belum optimal.