Determining the priority of flood risk zoning using geographic information system in Babolrud watershed (Mazandaran province)
Subject Areas : Applications in natural hazard and disasterKarim Solaimani 1 , Behrooz Mohseni 2
1 - RS & GIS
2 - Assistant Professor, Research Department of Natural Resources, Golestan Agricultural and Natural Resources Research and Education Center, Gorgan, Iran
Keywords: Land use change, Downstream, Zoning, Flooding, Flood flow coefficient.,
Abstract :
Due to the increase of flood incidents in recent years, the correct assessment of flood risk is one of the important components of flood reduction in urban areas. The purpose of this research is to create updated flood risk maps in the Babolrud watershed using synoptic station data and physiographic information (elevation, area, slope). Then, by using Geographical Information System (GIS), Landsat 8 satellite image and superimposition of layers (area, slope, land use, drainage density), flood potential was zoned. In order to prepare a flood risk map in the Babolrood watershed, the main factors affecting the occurrence of floods in the region were selected using relevant published sources and the opinions
of professors and experts, and a map of each factor was prepared by GIS software. The results of flood risk zoning showed that B2 sub- watershed has a higher flood potential than other watersheds. Sub- watershed B11121, B211INT, B11121INT and B211 were then identified in the next priorities in terms of flooding, respectively. Finally, based on the flood intensity index method, sub- watershed B11121, B211INT and B1INT with the highest flood flow coefficient were identified as the most flood sub- watershed. The results obtained from flood zoning in the region showed that the highest percentage of the watetshed area with 43.33% is allocated to zones with moderate flooding. In between, the lowest percentages are assigned to very low (0.64%) and high (7.33%) areas zones, respectively. According to the provided land use map, most of the flooded zones are related to residential areas or rainfed agricultural lands. Watercourses with ranked 3 and 4 are known as flood zones and flood control areas to the downstream areas. Watercourses with a rating of 5 and above are located in flood plains or river reaches and usually have shallow and widespread floods. Also, in some areas of the watershed, which have a relatively high altitude, the amount of runoff increases and causes flooding in the area. Therefore, monitoring the withdrawal of river loan resources in order not to destroy the river bed and constructions (Land use change) are among the priority proposals in this watershed.
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