Effects of Wildfire on Runoff and Sediment Production in Mellegue Watershed (Tunisia)

Mellegue watershed, located in the upper valley of Medjerda basin (North-West of Tunisia), plays a strategic role in the environmental protection and economic and social well-being for both the watershed and the entire region. It is characterized by a semi-arid bioclimatic stage, with an average annual rainfall of about 458.3 mm. The purpose of this paper is to study the impact of forest change on the hydrological behavior of Mellegue watershed. The methodology developed to map the impact of forest cover dynamics on hydrological behavior is based on analyzing fires that have occurred in 1992, from 2014 to 2021 in Nebeur forest (3714 km2). The relationship of forest–watershed is evaluated by delimiting burnt areas and calculating runoff and sediment volume using empirical formula. In fact, the methodology adopted is the realization of land use, fire, and rainfall maps, to estimate the runoff from the average rainfall, which will serve to estimate the solid contribution. The empirical formula applied for the calculation of the runoff is the Algerian one and for the calculation of the solid contribution is the one of Frigui. Thus, the average rainfall is determined by spatial interpolation of the closest rainfall stations of Mellegue watershed using ArcGis software. In the light of the maps and calculated values, graphs and curves have been developed, and we conclude that the runoff and sediment supply increase with the increase of the burned area from one year to another in an exponential way. In an overpopulated world, forests and the environment cannot be saved. Family planning is the primary strategic tool to preserve forests and restore environmental sustainability.