This article will detail the steps to model a sand trap in the HEC-RAS software and once modeled, which variables can be modified to obtain greater decantation of particles in the sand trap. The sand trap to be modeled is the one found in the Tablachaca dam. In the first place, the process of designing a sand trap and the variables involved will be explained. Then, it will be explained which variables of the sand trap and contour (environment) intervene in the modeling, to develop the numerical modeling in the HEC-RAS software. It has been determined that the sand trap is divided into 4 naves, each approximately 9 meters wide and 120 meters long, and, for modeling, it was decided to model a single nave. Data on the granulometry of the sediments and flows that reach the Tablachaca dam were obtained from previous works. When modeling the sand trap in HEC-RAS, there is a sedimentation layer...