The effect of water-spreading weirs of Gonabad city in reducing floods with different return periods (Case study: Riab watershed)

In arid and semi-arid countries such as Iran, which are always faced water supply problems in various sectors due to climate stress, the importance of surface runoff management in watersheds is becoming increasingly apparent. One of the components of water resources management in each region is the initiatives of people living in and around watersheds based on their indigenous and empirical knowledge. The purpose of this study is to investigate the effect of native water-spreading weirs in the Riab watershed on the reduction of floods resulting from maximum 24-hour rainfall with different return periods. The results show that the volume of floods generated from maximum 24-hour rainfall according to Lacey’s formula in the return period of 2 and 5 years are 5.35 and 7.17 million cubic meters, respectively, and in the return period of 10, 25, 50, 100, 200, 500 years, the flood volumes are 8.44, 10.09, 11.39, 12.73, 14.17, 16.21 million cubic meters, respectively. The water-spreading weirs created in the region with a flood volume of 8.36 million cubic meters have a great impact on the control of the floods created so that the floods created by the maximum 24-hour rainfall in the 2 and 5 year return periods are completely controlled and runoff does not leave the basin.