The Role of River Geomorphic Processes in Environmental Hazards of Songhor in Kermanshah Province

Most of time geomorphic processes that are created by fluvial systems cause environmental hazards in natural and human environment. In this paper, Songhor has been investigated on the basis of fluvial geomorphic processes. Hazards are studied in two parts, one of which is based on function of river and stream erosion (degradation, transportation and aggradation) and the others are hazards instigated from flood and storm-water. Therefore, firstly Songhor Chai basin was divided into two northern and eastern sub-basins. As Songhor city has located in the outlet of these basins, maximum discharge of flood was calculated for sub-basins by Dicken model. At second stage, longitudinal river profiles and the main stream were derived and analyzed. At the third stage, based on field observations and works using GPS, aerial photos, and GIS, geomorphologic map of the study area, the river hazard map and buffer zone of Songhor Chai River were drawn. Finally we found out that Songhor is under environmental and human-derived hazard threats due to factors such as the residential establishment on the flood plain in Songhor Chai river and streams, the construction of some parts of the city over the southern and eastern alluvial fans, and factors such as the encroachment to the river banks, and finally existence of loose colluviums in the banks. The inappropriate dimensions and elevation of Songhor Chai River Bridge can be also regarded as a threat.