Assessment of density area and LNRF models in landslide hazard zonation (Case study: Alamout watershed, Qazvin Province, Iran)

Abstract

Landslide is one of the natural disasters causing both life loss and financial damage. To plan and manage landslides better, it is necessary to produce landslide hazard zonation (LHZ) maps. Alamout watershed is one of the most susceptible landslides located in a mountainous area in north of Iran. At first, required information of layers such as geology, soil, elevation, slope, aspect, rainfall, and distance to fault, road, river, and land use factors from different sources were provided. Landslide inventory map was prepared using geological map, aerial photos and filed investigation with GPS. The map of each effective factor on the landslide was combined with the landslide distribution map to determine the weight of each factor. Landslide hazard zonation map was prepared with density area and LNRF methods in the Geographic Information System (GIS). The two models were evaluated with quality sum (Qs). Results showed that the density area method (Qs= 1.496) was more accurate than the LNRF model (Qs= 0.897). The results obtained from density area model indicated that very high hazard zones were approximately 33% of the study area. Additionally, low and very low hazard zones were almost 6.8% of the watershed. In the LNRF model, very low and low hazard zones were approximately 28% and high and very high hazard zones were 48% of the studying region.