Delineation of flood characteristics in coastal watersheds of Mazandaran (A Case study of Saraj’mahalleh watershed)

Contrary to popular belief, flood flows in the coastal watersheds of the northern hillsides of the Alborz which are mostly forested, cause damages. In this research, the flood characteristics in the watersheds have been investigated via a field study with a focus on the causes and consequences of the event in the Sarajmahalleh watershed of Galougah County. Results show that flood event in this watershed is a type of debris-mud flood consisting of coarse-grained sediments with mud and tree branches. High erodibility of geological formations, severe topography and low concentration time of flood currents are caused by the potential of debris floods in the watershed due to torrential rainfalls. Also, the study of vulnerable points confirms that the constructions of roads and intersection structures of waterways without considering the debris flow regime and regardless of the geomorphic characteristics of the watersheds overlooking them have intensified the damages caused by these events.