Urban and peri-urban drainage network representation using Geo-PUMMA in the Mercier (France) and El Guindo (Chile) catchments

Hydrological processes in urban and peri-urban areas are significantly affected by artificial elements like channels, pipes, streets and storm water networks. We present Geo-PUMMA, a set of GIS tools programmed in Python for GRASS that uses irregular vectorial meshes to explicitly represent the components of the peri-urban terrain. Geo-PUMMA gathers spatial information maps (e.g. cadastral, soil types, geology and digital elevation models) to produce Hydrological Response Units (HRU) and Urban Hydrological Elements (UHEs), and to improve the mesh for a better representation of water pathways. Geo-PUMMA also allows the extraction of basin morphologic properties such as the width-function, the area-function and the imperviousness-function. Geo-PUMMA was applied to two peri-urban catchments: the Mercier catchment (10% urbanized) located near Lyon, France, and the El Guindo catchment (40% urbanized) located in the Andean piedmont in the Maipo River, Chile. The comparison of width and area functions between the initial and recommended meshes shows that the drainage network representation is particularly improved at small to medium spatial scales (i.e. 120-150 m for the El Guindo catchment and 80-150 m for the Mercier catchment).