ANALISIS AMBANG HUJAN DAN PEMODELAN TANAH LONGSOR KABUPATEN KULONPROGO MENGGUNAKAN THE TRANSIENT RAINFALL INFILTRATION GRID-BASED REGIONAL SLOPE STABILITY MODEL (TRIGRS)

Kulonprogo Regency, Special Region of Yogyakarta is an area that has a high potential for landslides with a total of 208 landslides in 2020. The high rainfall intensity is one of the factor of triggering landslides. It causes the groundwater level and negative pore water pressure increase, then the positive pore water pressure is formed so that soil stability decreased.. The approach to determine the movement of soil due to changes in rainfall intensity is by empirical analysis using rainfall threshold for critical rainfall intensity and antecedent rainfall intensity. The rainfall threshold model in this study using empirical model (intensity — duration curve). This study analyzes the influence of the distribution of safety factor and pore water pressure due to changes of rainfall intensity and duration in Kulonprogo Regency using The Transient Rainfall Infiltration Grid-Based Regional Slope-Stability Analysis (TRIGRS) version 2.0 then visualized into a 2D spatial map using the Geographic Information System (GIS) program. The empirical equation for the rainfall threshold (intensity and duration) for critical rainfall intensity I = 85,21D-1,882 and antecedent rainfall intensity I= 147,07D-2,004. The resulting 2D spatial map shows that the increasing value of rainfall intensity causes the safety factor to decrease, pore water pressure increase, and the area that has high potential of landslide increase.