| Abstrak/Abstract |
Every year, landslide often occurs in the Tinalah watershed, Kulon Progo Regency. The frequency of landslide events increases after high rainfall intensity. Some factors control landslides, such as slope gradient, land use, geological structure, slope hydrology, and geological condition. This research aims to develop the susceptibility map of the Tinalah watershed and identify the rainfall threshold to trigger a landslide. The development of the susceptibility map using the frequency ratio method with four parameters, including slope, type of rock, land use, and lineament density. The landslide data were collected during the field survey and from the local disaster management authority (BPBD) Kulon Progo. Rainfall data were collected from Japan Aerospace Exploration
Agency (JAXA). Soil analysis also was conducted to develop a numerical model to verify the rainfall threshold value. The result shows a high susceptibility of the landslide area is dominated in Tinalah watershed. The rainfall threshold for the low susceptibility of the landslide zone is I = 490.14D−1.404 with 5–7 days of antecedent rain. The rainfall threshold for the medium susceptibility map is I = 164.32D−0.689 3–7 days antecedent rain. Moreover, the rainfall threshold for the high susceptibility of the landslide zone is 111.62D−0.779, with 2–7 days of antecedent rain. |
