Because of the global warming, the phenomenon of Solid Transport (bedloading transport and suspension transport), have increasingly serious impact on the normal function of hydraulic road drainage in the Higt atlas Morrocco. Indeed, they are clogged even if they are recently built, which generates the submersion and flooding of neighboring areas. This causes enormous material damage and threatens the safety of local residents.\nSo, in this work, we studied and quantified the solid flow as part as the design of hydraulic structure \" drain \" on flow crossing the Provincial Road RP 2010 in the “LAHJAR River Site” in the High Atlas Morrocco. The area study is located in the “Ourika” watershed. It is also called “LAHJAR” because il carries lot of pebbles each time the flood passes.\nWe tested the most widely used calculation methods worldwide in this study. After checking the field results (the 100-year solid deposition height at the structure = 1.5 m), we found that: \n- the formulas of Van Rijn, Engelund Hansen, Rickenmann gives values negligible. \n- the values from the formulas of Meyer Peter and Müeller, Watanabe, Ribberink, and Parker, are comparable to those observed.\n- the formulas of Schoklitsch and Sogreah, give excessive results.\nThus, this heigt of solid deposit is also important that liquid and must be considered in the design study.