Severe problems of denudation are happening in Tierra Blanca Joven pyroclasts within the Metropolitan Area of San Salvador, affecting infrastructure and housing projects. This leads to necessary and constant mitigation works. To understand the behavior and characteristics of these pyroclasts a monitoring program began. This was made through the installation in some sectors of 3/8 inch rods to recognize changes of erosion and sedimentation. With the help of remote sensors, historical changes were identified in the drainages. For this area a map of erodibility with the Universal Equation of Soil Loss was obtained. The results show the importance and influence of climatic factors, tectonic, human actions and changes of the base level of drainage. This can be used to build criteria for research and propose protection zones in the river drainage system. The monitoring probes to be useful and is necessary to improve it.