A Study of Landslide Occurrence in Relation to Land Use Changes and Road Construction Case Study Tadjan Watershed, Sari

Abstract
Recognition of effective factors on landslide occurrence and so high and low hazard region is one of the most important and necessary works for mitigation of landslide damages. In this study, from all of the effective factors on landslide occurrence, land use changes and road construction, into a parts of Tadjan watershed with area about 708.08 square kilometers in south of sari, was studied. In study area was detected 68 landslides with using aerial photos and comprehensive field works, then landslides was located by GPS and was mapped in GIS environment. Also, some information of landslide gathered by questionnaire and field works. For evaluating the effect of land use change in landslide occurrence, after preparing land use map and its correction with using interpretation of aerial photos dated 1373, questionnaire analyses, field works and using GIS software integration, it is indicated that 35.28 percent of landslides with area of 34.81 hectares was occurred in regions that land use transformed from forest land to dry land farming and garden. Also, after preparing of roads map with using topographic map and its correction with aerial photo, analysis of questionnaire information and GIS techniques, it is concluded that most landslide occurrence density was take placed into maximum distance of 75 meters from road with 21 landslides and density of 0.219 ( per square kilometer).

Keywords: Aerial photos interpretation, Land use change, Landslide, Road construction, Tadjan Drainage Basin.