Landslide Zoning and Mitigation in Clapar Area, Madukara District, Banjarnegara Regency, Central Java

Abstract

Landslide disaster is one of the most frequent disasters in Clapar, Banjarnegara. Landslide is a recurring event and there is no suitable method to respond the threat until now, so that preventive stage have not been maximized. The scienstist explains that the movement of land in the area is very active, but the level of activity that can cause landslides can’t be known qualitatively or quantitatively. The method that used to achieving these purposes is geology and landscape morphology mapping in areas that have been and have possibility landslide disaster. Factors that controls the landslide motion are geomorphology, rock type, geological structure and land use, while the triggers are water infiltration and rock fractures. Slope in Clapar is 30 - 70% and the rock type is clay with quarzite and chert fragments from Totogan Formation, volcanic breccia from Tapak Formation, and polimictic breccia from Ligung Formation. Geological structure that found is right slip fault (Rickard, 1972) with the strike and dip of fault is N 359oE/79o. The land usage are pine forest, salak farm, and settlement. Angle of shear strength from direct shear test soil sample in Clapar slope is 27o with safety factor value is 1.045 included in the critical class. According to those existing datas, Clapar included into area that are very vulnerable to landslides. It is because this area was affected by major slip fault and steep angle. The most land usages is salak farms which is the plants has fibrous root that control the properties of soil. It makes the water easily infiltrate into the soil that causes increase the weight of the soil and make the plane become slippery.