Generating regional rockfall hazard model at along mountainous roads by using of overlay index and GIS (Case study: Kurdistan, Salvatabad saddle)

The aim of this research is generating rockfall hazard zonation map by using of overlay index method in Salavatabad saddle that is located in Sanandaj southeastern، Kurdistan province. The first، in this research، we using of field search، local interview and review on carried out studied in the outside and inside of Iran، eight factors effective was recognized on rock falls. These factors include; slope degree، slope aspect، slope curvature، elevation، distance to road، distance to fault، litology and land use. After recognizing، we act to processing with Arc view 3. 2 and ERDAS imagine 8. 5 software. Thirty four Sensitive slopes were used as prone slopes to rock fall data (Dependent variable). For statistical analysis، be used of likelihood ratio statistical analysis. At this research، the value of each various class between 0 and 1 is determined. As for، the chart be obtained from overlay distribution rockfall map with information layers، the each of class of each layer that had more frequent density، 10 value and other classes with aspect of value of rockfall frequent density in class itself، was determined as unit of 100 value. With transmit this coefficient to each class and wights based on the charts as effective factors with rockfalls and expert opinions، the hazard zonation susceptibility of rockfall was generated in Salvatabad saddle regional with five classes. For Verification، rockfall point’s map was overlaid with hazard map. For more confidence، first each of effective variables removed then hazard Zonation map was generated and at last this map was verificated. Result have shown that percent of verification without slope degree is 75. 81 percent، without slope aspect is 78. 50 percent، without elevation of sea is 72. 16 percent، without litology is 74. 64 percent، without distance from road is 76. 23 percent، without distance from fault is 73. 56 percent، without curvature is 64. 00 percent، without landuse is 74. 23 percent and by all variables the percent of verification is 81. 44 so، it is high and acceptable..