Effect of Construction of Narmaab Storage Dam on Reduction of Flood Plain and Flood Damage at Downstream Lands

Flood is one of the complex and destructive natural phenomena led to human and financial losses around the country and world every year. Generally methods of flood controlling are classified in two parts consist of structural and non structural methods. Construction of dam is one of the structural methods plays an important role in flood control. A dam by storing a part of flood volume causes to dropping in flood peak and reduces the flood damage in down lands. In this study, by using of river analysis systems(HEC-Ras) and geographic information system(GIS) and utilizing of Google-Earth software, the floodplain with frequency of 50, 100, 500 and 1000 years investigated at Narmaab River of Golestan. Then effect of construction of Narmaab Dam on reducing the flood plain at down lands has been studied. Therefore several scenarios were defined for dam flood storage volume and in any case the flood plain and flood damage at down lands was estimated. The results show that construction of Narmaab Dam with a flood storage volume equal to 6 million cubic meters can reduce damage of flood with frequency of 50 and 1000 years by %75.1 and %40.7 respectively.