Protecting the population and property against floods is one of the Moroccan National Water Plan priorities. Indeed, based on the National Flood Protection Plan established in 2002 and updated in 2017, 1,032 vulnerable sites were identified with different risk levels: low, medium and high. In the North West part of Morocco, the Gharb plain has experienced many flood events, the most devastating is the one occurred on 1970 and has caused many causalities. The floods affect negatively the irrigation network of the Gharb plain and hamper the optimal water resources management in the Sebou basin. Al Wahda Dam was built in 1996, with a total capacity of 3.7 billion of cubic meter, and an objective of ensuring both the irrigation and the protection of the Gharb plain against flooding. Since that, the dam contributed effectively on the protection of the downstream region. However, with increasing extreme events frequency the region has experienced significant floods (2009 and 2010). The scope of this paper is to examine the opportunity of constructing large dams upstream Al Wahda dam to ensure an effective flood risk management by increasing the capacity of the dams to handle extreme floods. The hydraulic simulations were carried out with the decision support system for integrated water resource planning and management RIBASIM. The results showed that the increase in the storage capacity upstream of Al Wahda, will not be sufficient on its own for the protection of the Gharb plain against flooding, but we must think of other actions to be implemented downstream of the Sebou river.