Evaluation of the potential flooding of Ziarat watershed by CN-based method and WetSpa hydrological model

Floods are one of the natural disasters that cause many financial damage and loss of life in worldwide. In general, it could be said that the runoff coefficient is the best indicator which can represent the flooding situation in the watershed. Runoff coefficient is the ratio of rainfall that flows on the ground and its value varies from zero to one. Therefore, providing an appropriate map with most similarity to the reality can be the facilitator of many flood control planning. For this purpose, the runoff coefficient map was compiled by two methods and then was compared. The first method is an experimental and CN-based method that is common among researchers and the second one is using the WetSpa spatially distributed hydrological model. Therefore, the average weight of flooding potential coefficient map which prepared by SCS method was 0.045 and by WetSpa model was 0.714. Finally, for understanding the results of these two methods, the daily average of flooding potential coefficient was compared using daily rainfall and runoff data recorded over a four years period. Since the estimated runoff coefficient was 0.47, which is closer to the results of the WetSpa model, so the WetSpa model performed better. However, due to the fact that each of two methods has unique features (for example, the WetSpa model needs more data and details but on the contrary, SCS model needs less data and details), both of these has different uses which can be effective in certain situations.