Table 1 Causal factors and their significance for landslide occurrence with the references
Causal factors | Significance | Classes | Methods | Data source |
|---|---|---|---|---|
Slope Angle | Slope gradient, a predominant factor for mass wasting (GarcÃa-RodrÃguez et al. 2008; Corominas et al. 2014). Steeper the slope gradient higher the chance of landslides (Kamp et al. 2008) | 6 | Equal interval | ASF DAAC (2015) |
Aspect | Related to the weather condition, weathering and land cover thereby affect the occurrence of landslides (GarcÃa-RodrÃguez et al. 2008; Kamp et al. 2008; Corominas et al. 2014) | 9 | Categorical factor | ASF DAAC (2015) |
Elevation | Slope instability could be the result of changes in elevation (Corominas et al. 2014). The region having higher elevation mostly dominated by rocky slopes where the frequency of earthquake-induced landslides is higher (Owen et al. 2008) | 6 | Equal interval | ASF DAAC (2015) |
Geological formation | The strength and permeability of the slope is depending on the lithology of the area thereby, is crucial conditioning factor for landslide occurrences (Dai and Lee 2002; Corominas et al. 2014). We used geological formation according to the data availability as lithology varied according to the formation in the study area | 6 | Categorical factor | DMG (2021) |
Land cover | Mechanical anchoring of the land depends upon the land cover (Meusburger and Alewell, 2008) and is highly important conditioning factor for landslide occurrences (Montgomery et al. 2000; GarcÃa-RodrÃguez et al. 2008; Corominas et al. 2014) | 7 | Categorical factor | ICIMOD (2013) |
Distance to the river | Landslide distribution is related to the distance to the river (Mancini et al. 2010; Corominas et al. 2014) | 4 | Buffering by defined class | ASF DAAC (2015) |
Distance to road | Road cuts are usually instable as it changes the topography (Yalcin 2008; Xu et al. 2012)Â and creates the favorable environment for landslides (McAdoo et al. 2018; Pourghasemi and Rahmati 2018) | 10 | Buffering by defined class | Drawn using GE image |
Soil type | Crucial for shallow landslides and highly important factor for large landside occurrences (Corominas et al. 2014) | 6 | Categorical factor | Dijkshoorn and Huting (2009) |
Total Curvature | Curvature, a topographic factor, crucially important for rock fall and highly important for shallow landslides (Hasegawa et al. 2009; Corominas et al. 2014) | 6 | Natural breaks | ASF DAAC (2015) |
Seismic intensity (PGA in %) | Earthquake shaking act as an additional driving force on the slope which favors the landslides (Duncan et al. 2014; Corominas et al. 2014; Budimir et al. 2015): higher the energy of shaking, higher the risk of slope failure (Keefer 2002; Delgado et al. 2011). We considered the peak ground acceleration (PGA) to understand the ground shaking following the study by Xu et al. (2012) | 4 | Categorical factor | USGS (2015) |
TWI | It contributes for the hydrological processes and is considered as important causal factor for landslide occurrences (Xu et al. 2012; Fan et al. 2019) | 5 | Natural breaks | ASF DAAC (2015) |
Distance to the fault | Distance to fault is highly relevant as both landslide conditioning and triggering factor (Corominas et al. 2014). Local fault and thrust (reverse fault) located inside the study area were buffered for the distance to fault | 7 | Buffering by defined class | DMG Nepal (2021) |
Flow Accumulation | Used in hydrological modelling and is crucial for landslide occurrences (Corominas et al. 2014) | 10 | Geometric interval | ASF DAAC (2015) |