The role of flood routing in determination and Prioritizing hydrologic units Bostan Dam Basin from flooding and showing management technique

Subject Areas : Farm water management with the aim of improving irrigation management indicators

Seyed Alireza Bahrami ¹ (M.Sc. of watershed management, Faridan watershed management and natural resources department. Iran)
Majid Onagh ² (Professor of desert management department, University of Natural Resources, Gorgan, Iran)
Hasan Farazjoo ³ (M.Sc. of Golestan Water Authority. Iran)

Received: 2011-06-14 Accepted : 2011-10-27 Published : 2011-12-15

Keywords: flooding Bostan dam basin, Flooding, flood routing, HEC-HMS model,

Abstract :

Determining flood producing regions and sub-basins flood producing priorities are considered very important in the management of large watersheds. In this paper the flood routing role in separating and determining flood producing regions in the Bostan dam watershed of Golestan province in northern Iran after discharge routing of sub-basins in main waterways up to the main outlet of watershed was studied. For achieving the above goal, geographical information system (GIS), a hydrological model (HEC-HMS) and individual iterative elimination of sub-basins was used to calculate related hydrographs with design precipitation for each sub-basin. With consecutive elimination of sub-basins in each run of the model, the total discharge from whole watershed basin after flood routing in main waterways with considering the eliminated sub-basin was calculated; therefore effect of each sub-basin in flood producing capacity at the main outlet was determined. The sub-basin, with highest contribution in producing watershed outlet flood was recognized as most producing flood sub-basin. Then other sub-basins were ranked according to their quantitative share in producing flood discharge at outlet. Flood routing in waterways showed that contribution rate of sub-basins in outlet flood was not proportional with peak discharge of sub-basins and those sub basins with higher discharge do not necessarily have the highest contribution in basin's outlet flood, since waterways parameters of routing and the spatial location of sub-basins can change the contribution status. In order to eliminate the area effect in sub-basin ranking, the degree of influence of every sub-basin unit in the outlet flood was calculated, which changed the flood producing ranking of sub-basins. Finally with respect to the obtained results, required management guidelines were suggested.