Topographic maps and Geographic Information Systems (GIS) through the application of spatial analysis tools derived from Digital Elevation Models (MED), constitute a fundamental resource in the management of hydrographic basins and territorial planning. The objective of this work is to delimit flood risk areas by applying MED, taking as a case study the El Estero stream micro-basin, San Ramón in Costa Rica, which is located on the left and upper bank of the Río Grande de San Ramon. The spatial analysis allowed us to show all the topographic conditions of the microbasin and precisely delimit the stream valley, revealing those areas of the microbasin that are prone to flooding. This research not only shows how the use of DEMs and their derived products allows a detailed study of some of the variables that influence the production of flood sites but is also an indispensable tool in urban planning.