Flowpaths are significantly affected by land use change and engineered elements across urban catchments. Conventional GIS-based tools for extracting drainage networks were not developed for urban terrains. This work presents Geo-PUMMA, a GIS toolbox to generate vectorial meshes for terrain representation in distributed hydrological modeling, and to extract drainage patterns in urban and peri-urban catchments. Geo-PUMMA generates well-shaped Hydrological Response Units (HRUs) and Urban Hydrological Elements (UHEs). The toolbox was used in peri-urban catchments of Chile and France to generate three model meshes with different levels of treatment, and extract and compare their corresponding drainage networks. A recommended mesh is identified, which replicates the main morphological and hydrological features of the reference drainage network, and is able to preserve features at small to medium spatial scales (similar to 80-150 m). Overall Geo-PUMMA can be used to represent the terrain in distributed hydrological modeling applied to urban and peri-urban scales. (C) 2017 Elsevier Ltd. All rights reserved.

Sewer systems affect urban soil characteristics and subsoil water flow. The direct connection observed between baseflow in sewer systems under drainage infiltrations and piezometric levels influences the hydrological behavior of urban catchments, and must consequently be considered in the hydrologic modeling of urban areas. This research studies the groundwater contribution to sewer networks by first characterizing the phenomenon using experimental data recorded on a small urban catchment in Nantes (France). Then, the model MODFLOW was used to simulate the infiltration of groundwater into a sewer network and model dry weather flows at an urban catchment scale. This application of MODFLOW requires representing, in a simplified way, the interactions between the soil and the sewer trench, which acts as a drain. Observed average groundwater levels were satisfactorily simulated by the model while the baseflow dynamics is well reproduced. Nonetheless, soil parameters resulted to be very sensitive, and achieving good results for joint groundwater levels and baseflow was not possible.

Stormwater quality modeling remains one of the most challenging issues in urban hydrology today. The processes involved in contaminant generation and transport are very complex, with many associated uncertainties, including uncertainty arising from process variability. In this study, the spatio-temporal variability of build-up/wash-off processes in a heterogeneous urban catchment within the Parisian region is assessed based on three stochastic modeling approaches integrated into the physically based distributed hydrological model, the Urban Runoff Branching Structure (URBS) model. Results demonstrate that accounting for process variability at the scale of a hydrological element is important for analyzing the contamination recorded at the catchment outlet. The intra-event dynamics of total suspended solids (TSS) were most accurately selected for the stochastic exponential SWMM model, as this model succeeded not only in simulating the general trend of TSS concentrations fluctuations but also in replicating multiple peaks observed in pollutographs. The advantage of this approach is that it captures the stochastic nature of the processes with minimal prior knowledge and without extensive calibration, though further enhancement is necessary for it to become a useful tool to support decision making.