LAUSR

The upper Cimanuk drainage basin is an inter-mountain basin. It is surrounded by volcanoes such as Mt. Tampomas, Mt. Guntur, Mt. Dano, Mt. Kamasan, Mt. Papandayan, and Mt. Cikuray. The objective of this research is to identify the degree of tectonic activity based on quantitative geomorphology analysis. Data are obtained from a topographic map, Digital Elevation Model, geological map, and field observation. Various morphometric variables are bifurcation ratio (Rb), drainage density (Dd), and mountain front sinuosity (Smf) index. The integrated analysis of morphometric and field data provides evidence of tectonic activity in Cimanuk drainage basin. Their streams have 1st until seventh order. The research area is proved to be an active tectonic area. This is confirmed by values of Rb, Dd, and Smf showing that some area in Cimanuk drainage basin has been affected by the tectonic activity. Rb values are ranging from 0.74 to 3.99, Dd values are ranging from 0.53 to 7.20, and Smf index area ranged from 1.2 to 1.6. These values can be classified into a medium class of tectonic activity level. The geological structure can be found in the middle to downstream of Cimanuk drainage basin and showed by primarily northwest-southeast trends. On the other hand, drainage pattern such as rectangular and trellis can reflect geological structures. Rectangular control is by joint and fault structure whereas trellis by dipping or folded sedimentary rocks. The Jatigede Reservoir is located in a strongly deformed area, so monitoring is necessary to reduce the impact of the disaster if some of the faults in the area are active again.