Hydrocarbons are exploited within a sedimentary basin using a stratigraphic simulation coupled with a hydrologic model and a terrestrial organic matter accumulation model. The inorganic sediment distribution within the basin is determined with a stratigraphic simulator for at least one time step. Then, at least one unsaturated zone is delimited within the basin using a hydrologic model. At least one zone of terrestrial organic matter accumulation within the basin and an amount of terrestrial organic matter accumulated in this accumulation zone are determined by a model of the terrestrial organic matter accumulation as a function of the unsaturated zone thickness, of the unsaturated zone thickness stability and of the surface water flux defined for the time step considered.