Investigation of the Possibility of Avalanche Occurrence Prediction Using the Nearest Neighbour Method (Case Study: Paths of Avalanche Release in Tehran Province)

Avalanche occurrence is one of the natural disasters that caused loss of life and damages in most mountainous areas of the world every year. Phenomenon of avalanche downfall in Iran is caused to irreversible damages, specially on residents and passing travelers through mountainous roads (Dizin - Gagereh, Haji Abad - Dizin, beginning Karaj - Chalus, Karaj - Chalus middle, Haraz and Imam Zadeh Davoud) in Tehran province. Unknowing the time of avalanche occurrence, exceeds the damages. Then, forecasting the avalanche occurrence probability in the avalanche paths help to reduce human and financial damages of passengers and residents. For investigation the probability of avalanche occurrence in this region, the nearest neighbor method was used. This method carried out based on the avalanche information and daily data of snow in the 22 snow stations during 10 years (from 1377-78 to 1387-88). In this method, the number of similar snowy days that were created former avalanches was determined using ArcGIS software. Then, by snow zoning in different months of investigative year by using kriging method, the rate of snow depth variations (that generates avalanche) were obtained. Thereafter, warning level, positive neighbor's ratio (NN ratio) and probability of avalanche occurrence were characterized in the every path. The results showed that in most communication paths, avalanche phenomenon has occurred in snowy months and probability in month of March is more than other months. The important reason of this phenomenon is high snow depth and increasing the temperature. Finally, probability of avalanche occurrence in Dizin – Gajereh path and Karaj – Chalous path was predicted very high. The reason of this point could be topographic conditions (high slope, slope subject to the sun), rock and mostly climate conditions (high snow depth, snow wind and temperature). The results of this research project can help to managers of avalanche control, effectively as they warn people to avoid from non - essential travels in that time or choose the other paths.