Application of Rain Barrels for Flood Control in an Urban Mountain Basins

In urban basins the increase of urbanization has caused an important alteration of the hydrological cycle, reflected in: increases in discharge peak, runoff volumes and flow velocities; these changes are increasing the risk of storm floods. This research examines this problem in a small city located in the Colombian Andes, where the problem is even more critical due to high slopes increment the velocities of flow even more. In mountain watersheds exist few literature about this problem, for that reason it has been studying a zone named San Luis-Palogrande watershed with an area of ​​1 km², represented by 70.9% of urban area and a forested zone of 29.1% of the total area, and slopes that ranges from 1.2% to 34.5%. The research aim is to adapt Sustainable Urban Drainage Systems (SUDS) to mountain watershed conditions, therefore the study area is been modeled with the hydrodynamic model SWMM. The parameters were obtained from: land use map, aerial photography, soil map generated from soil samples, contour lines every 2 m and sewage network map, which was completed from field data and secondary information. The area has 4 meteorological stations and 1 hydro-meteorological station that measures discharge at the outfall. 5 events were taken for the calibration and 13 for validation, obtaining calibration fitness of the model with Nash coefficient of 0.76-0.93 and 0.65-0.88 for validation (considered good fitness). With the validated model test are been carried out to adapt SUDS to these conditions, by using small scale rain barrels in a first attempt. Most SUDS require large areas, which in this case it is not possible because is a mountain city with space limitations. Another common type of SUDS uses infiltration what cannot be use here because the large quantity of landslides that are triggered from soils and topography.