Hulu Kelang, Malaysia regional mapping of rainfall-induced landslides using TRIGRS model

Rainfall-induced slope failure is one of the most destructive natural disasters that occur frequently in natural or engineered residual soil slopes. Rainfall-induced slope failures often occur as a shallow slope failure, with slip surfaces orientated parallel to the slope surface, especially in Hulu Kelang areas where a residual soil profile has formed over a bedrock interface. The possibility of using the transient rainfall infiltration and grid-based regional slope stability analysis method (TRIGRS) is applied to unstable slopes and three rainfall threshold chart conditions that result in landslides in the study area. We compare the intensity–duration of 3-day rainfall threshold charts (I–D)3, cumulative 30-day rainfall–number of rainy day (API30–N), and cumulative 3-day rainfall–30-day antecedent precipitation index threshold chart (E3–API30) conditions capable of producing slope instability in the study area predicted by TRIGRS, with empirical rainfall I–D thresholds for possible landslide occurrence in the northeast part of Kuala Lumpur. The results showed that TRIGRS is capable of reproducing the frequency of the size of the patches of terrain predicted as unstable by the model, which match the frequency size statistics of landslides in the study area, and the rainfall threshold based on the E3–API30 threshold chart could give a better prediction to a landslide than other conditions in Hulu Kelang area. Our results are a step towards understanding the mechanisms that give rise to landslide regional modeling.