Abstract. The diversion of natural river courses and subsequent filling by alluvial deposits or anthropic intervention has been hidden by urban development in the majority of the cities. The research we conducted involved monitoring the evolution of a river course and reconnaissance of the original morphology of the fluvial systems. Our research was applied to the section of the River Beiro that flows through the city of Granada, Spain. The research has been carried out using geo-technical methodology based on reconnaissance via dynamic penetration. This allowed us to determine the different degrees of consolidation and compaction in the areas corresponding with the former course of the river, which are now filled by alluvial deposits. In addition, we have backed up our findings with information provided by historical maps of the city of Granada. The results have identified an area wherein buildings are at risk, as evidenced by the detrimental effects registered in the buildings in this area.