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# Probabilistic landslide hazard assessment using homogeneous susceptible units (HSU) along a national highway corridor in the northern Himalayas, India

Landslides (Impact Factor: 2.09). 04/2012; 8(3):293-308. DOI:10.1007/s10346-011-0257-9

ABSTRACT The increased socio-economic significance of landslides has resulted in the application of statistical methods to assess their
hazard, particularly at medium scales. These models evaluate where, when and what size landslides are expected. The method presented in this study evaluates the landslide hazard on the basis of homogenous susceptible
units (HSU). HSU are derived from a landslide susceptibility map that is a combination of landslide occurrences and geo-environmental
factors, using an automated segmentation procedure. To divide the landslide susceptibility map into HSU, we apply a region-growing
segmentation algorithm that results in segments with statistically independent spatial probability values. Independence is
tested using Moran’s I and a weighted variance method. For each HSU, we obtain the landslide frequency from the multi-temporal data. Temporal and
size probabilities are calculated using a Poisson model and an inverse-gamma model, respectively. The methodology is tested
in a landslide-prone national highway corridor in the northern Himalayas, India. Our study demonstrates that HSU can replace
the commonly used terrain mapping units for combining three probabilities for landslide hazard assessment. A quantitative
estimate of landslide hazard is obtained as a joint probability of landslide size, of landslide temporal occurrence for each
HSU for different time periods and for different sizes.

KeywordsLandslides–Hazard–HSU–Segmentation–Himalayas–India

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