ریز پهنه‌بندی خطر سیلاب در محدوده شهر نیشابور در راستای توسعه شهری

A region of 390 square kilometers of neyshabour was selected for flood zoning. this region is divided into the city and hydrographic networks. this confined area includes three geo-morphological part namely mountain, plain head (along alluvial fans) and lowland. a part of the city is located in plain geomorphology unit and the other part is laid in the mountains area that covered surface of alluvial fan. the study on the desired area was conducted as follows: the study area is too wide therefore, it is divided into 3 sub-basins; then, the effect of urban development on the basin was estimated through topographic maps, aerial photographs and field visits. the maximum flood event of every basin is calculated by a 100- year return period. the purpose of this calculation is estimating the maximum flood volume which is entered into the urban of the mentioned basins. by providing the required layers for both the city and the basin area of the study, the weight of each layer is determined based on its importance in the occurrence of floods. (importance of each layer was determined based on the opinions of experts in various organizations of neyshabour). after the final weighing, the layers were compared with each other and the resultant matrix of these comparisons is used in idrisi and eventually final coefficients were determined for each layer. finally, by applying these coefficients through raster calculator in arcgis, maps of flood hazard zoning in the basin were determined and the boundaries of neyshabour were specified separately.thus, the critical boundaries of urban area against flood were defined and flood damages in the form of the maps of the damage assessment were presented.