Debris retention dams are one type of critical protection structures implemented in torrents in order to provide protection against natural phenomena. They mainly aim in moderating, through their openings, the passage of the flow to the downstream where elements at risk are located. This is achieved by storing specific volumes of debris materials in their upstream debris basins and then, eventually, releasing this volume with a lower discharge. The filling of a debris basin by debris material over time, reduces the efficacy of the dam in achieving its functions. Consequently, cleaning maintenance operations of a debris basin should be regularly performed. This necessitates high monetary budgets, which can not be always affordable by the State for the management of protection structures in mountains. This paper proposes a model that makes it possible to model the passage of debris flows through retention dams. The case of the Claret retention dam in France is considered, in which the proposed model is used to analyze the performance of the dam considering its initial and new designs. A numerical analysis, over a period of 50 years, is performed using real data. The obtained results permit the managers of the Claret to figure out which of the designs is more favorable in terms of reducing maintenance costs and in terms of increasing protection efficacy.