In Tunisia, floods are frequent and dangerous. Every year, several regions of the country are affected, and human losses and property damage are recorded. The city of Boussalem is located in a Mediterranean region that faces flood phenomena affecting arid and semiarid areas. These floods, which are sudden and often difficult to predict, with a rapid rise time and a relatively high specific flow rate, are generally linked to rainy episodes that occur in moderately sized basins. The Tunisian government is currently deploying means to anticipate and tackle this phenomenon. Dredging work on the Medjerda river and some of its tributaries began in 2015 in order to limit this damage, and to protect the bordering cities from flooding. The present work focuses on the study and modelling of the impact of the dredging works on reducing flooding, especially in the Boussalem region. For this purpose, a new 1D-2D coupling methodology was developed using the HEC Ras software. The combined simulation results showed a significant reduction in the flooded area in Boussalem city after the dredging work for the 10-year return period, hence the importance of bottom maintenance on flood control. Flood risk maps were also developed for the 50- and 100-year return periods to predict future flood risks.