The spatio-temporal dynamic of land use in the Bonoumin and Gourou watersheds, over the last three decades (1990 to 2020), were analysed using Landsat images (1990, 2005 and 2020), remote sensing and a geographic information system (GIS). The main objective of this study was to analyse the impact of changes in land use in these two watersheds on stormwater runoff, which is responsible for flooding in the study area. The methodology adopted consisted of first downloading the Landsat images, which were then pre-processed, before undergoing several processes, leading to the classification and analysis of land cover dynamic. Maximum likelihood supervised classification was applied. Thus, the results of this classification showed that over the last three (03) decades, the impermeabilised surfaces in the two watersheds, represented by the medium and highly densified urban areas, have increased significantly, unlike the vegetated surfaces, which have decreased significantly. The increase in impermeable surfaces reduces the capacity for water to infiltrate the soil and increases the amount of runoff. The results also showed that in recent years, the upper reaches of the Bonoumin watershed have come under considerable anthropogenic pressure. This means that in a few years time, there will be a sharp increase in the amount of runoff water in the lowlying areas of this basin, and therefore an increase in the risk of flooding.

Soil erosion by precipitation, rainfall and runoff is a widespread phenomenon in different countries of the world. It becomes disastrous in particular on the slopes because of the torrentiality of the flow, of the strong vulnerability of the grounds (soft rocks, fragile grounds, steep slopes). The present study has for objective: The analysis of the data of concentrations of sediments in suspension are measured at the station of the rivers highlights relations, linking the concentration (or the solid flow) of the sediments in suspension to the liquid flow and to quantify the seasonal, monthly and interannual and intra annual variation of the surface degradation. Annual tonnage estimates of solids loads to the Mé were derived from the power law for all seasons. From this deduction, the annual quantities of sediment transported by the Mé from 2015/2017 is 7.06.106 t/year, or a specific degradation of 1.79.103 t/km2/year. On the other hand, in 2017, the value of this solid input is 3.06.106 t/year. However, the annual solid input is estimated at 7063.03.103 t/year with a specific degradation of 1784.47 t/km2/year at the Mé from 2015 to 2017.

This theoretical article aims to make a state of the art on prospective studies applied to the dynamics of land use and the use of water resources. As a first step, it presents a general overview of prospective studies by providing a refined and consensual definition of foresight, by presenting a brief history of the evolution of prospective studies worldwide, by presenting the scenario method in prospective and the two big families of scenarios (exploratory or forecasting and normative or backcasting). In a second step, he tackles the question of the prospective study and the dynamics of the occupation of the soil and use of the soil. Thirdly, it presents prospective studies and water resources on a given territory.