In the current situation of the Brazilian semiarid region, which depends highly on the hydraulic reservoir structures, an adequate design of water resource structures and maintenance of those already in operation is an essential factor to guarantee water supply and ensure the safety of the population who are downstream of the dam. Based on these necessities, a correct structural filter design is necessary, attributing its efficiency to the ability in preventing any internal erosion process. However, most of the dams in operation were designed before the publication of the present filter design criteria and those structures either do not have filters or have not a proper filter design, becoming more vulnerable to an eventual internal erosion process. The situation is further aggravated for embankments in the region with frequent droughts, due to constant drying and filling cycles of the reservoir, resulting in drainage system failure concerning to the soil fatigue during those cycles. It is therefore necessary methodologies for evaluate the risk of these structures against internal erosion process. This study describes an estimation for the effectiveness of the filter structure in the embankments, by using a numerical simulation of the contacts between the different soils and the structure through a geometric-probabilistic methodology, and using as input data the grain size distribution of the soils presents in the dam. The numerical modeling uses an alternative method of sizing filters, which correlates a theoretical approach of the subject. The dams select for the case study are Taquara, Olho Dagua, Figueiredo, Monselhor Tabosa, Itauna and Gangorra, all of them located in Ceara State, Brazil.