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Quantifying urban runoff during frequent rainfall events is a key element in quality management of urban water due to their high contribution to the annual runoff flow. This explains the growing interest among hydrologists in studying runoff flow on urban surfaces. In this paper, we review most of the experimental approaches as well as the modeling ones conducted in the literature to understand and estimate runoff flow on urban areas. This review highlights the incoherence between our current understanding of the hydrological behavior of urban areas during frequent events and our conception of the loss functions in the urban drainage models. Field studies provided more insight into the determinant processes occurring on the different surface types during frequent events with depression storage being a fundamental element varying between surface types and for the same surface type and infiltration process being relatively important on paved areas especially in their cracks that constitute preferential pathways for rainwater. Analyzing a wide range of urban drainage models showed that these elements along with the temporal evolution of the hydrological behavior of urban surfaces due to seasonal and state conditions are not fully integrated in the models’ structures, which were initially developed for heavy rainfall events. Adapting the assumptions of urban drainage models based on these new factors must improve the performance of hydrological models for frequent rainfall events.

Hydrological behaviour of roads concerns environmental issues, as pollution by rainwater runoff or urban heat island, and road safety issues. The few studies devoted to the subject concluded that runoff losses are non-negligible and poorly understood. The objective of the study is to better describe runoff losses over asphalt concrete plates of around 0.5 m 2 area. An urban lysimeter has been developed to measure by weighing the partition of rainfall on the plate: storage at the surface and in the pore of the plate, surface runoff, infiltration at the bottom of the plate and evaporation at the surface of the plate. Three plates have been tested outdoor during 5 months each. One of them is a porous asphalt concrete. Results show that runoff losses are significant. They represent 30% of the rain for the traditional plates and 84% of the rain for the porous plate. Losses are mainly due to infiltration (58%) and evaporation (25%) for the porous plate. For traditional plates, evaporation is similar to the one measured for the porous (25% of the rainfall), but infiltration at the bottom is negligible (3%).

International audience; The database of the Reze urban catchments rates from two small catchments recorded continuously France includes not only rainfall and flow with a time step of 1 min over a 7-year period, but also tensiometric, piezometric, and meteorological measurements. database has been complemented by information on the catchments through the Internet file transfer protocol. themselves of digitized land use and topographic maps. This database is regularly updated and available to researchers

Runoff on impervious surfaces (roads, roofs, etc.) raises a number of environmental and road safety-related problems. The primary objective of this research effort is to improve our knowledge of the hydrological behaviour of impervious urban surfaces in order to better assess runoff on these surfaces and its subsequent consequences. This article will focus on two street stretches studied over a 38-month period. Measurements of rainfall and runoff discharge on these stretches have made it possible to estimate runoff losses as well as to constitute a database for modelling purposes. On the basis of these data, two models have been used, one simple the other more detailed and physically based. For both models, runoff discharges at a 3-min time step are well reproduced, although runoff coefficients and runoff losses are still poorly estimated. Detailed analyses of experimental data and model output, however, indicate that runoff losses could be quite high on such ‘impervious surfaces’ (between 30 and 40% of total rainfall, depending on the street stretch) and that these losses are mainly because of evaporation and infiltration inside the road structure. Copyright © 2011 John Wiley & Sons, Ltd.

This paper presents the hydrological component of the Submesoscale Soil Model, urbanized version (SM2-U). This model is an extension of the rural Interactions between Soil, Biosphere, and Atmosphere (ISBA) soil model to urban surfaces. It considers in detail both rural and urban surfaces. Its purpose is to compute the sensible heat and humidity fluxes at the canopy–atmosphere interface for the computational domain lower boundary condition of atmospheric mesoscale models in order to simulate the urban boundary layer in any weather conditions. Because it computes separately the surface temperature of each land use cover mode while the original model computes a unique temperature for the soil and vegetation system, the new version is first validated for rural grounds by comparison with experimental data from the Hydrological Atmospheric Pilot Experiment-Modélisation du Bilan Hydrique (HAPEX-MOBILHY) and the European Field Experiment in a Desertification Threatened Area (EFEDA). The SM2-U water budget is then evaluated on the experimental data obtained at a suburban site in the Nantes urban area (Rezé, France), both on an annual scale and for two stormy events. SM2-U evaluates correctly the water flow measured in the drainage network (DN) at the annual scale and for the summer storm. As for the winter storm, when the soil is saturated, the simulation shows that water infiltration from the soil to the DN must be taken care of to evaluate correctly the DN flow. Yet, the addition of this soil water infiltration to the DN does not make any difference in the simulated surface fluxes that are the model outputs for simulating the urban boundary layer. Urban hydrological parameters are shown to largely influence the available water on artificial surfaces for evaporation and to influence less the evapotranspiration from natural surfaces. The influence of the water budget and surface structure on the suburban site local climatology is demonstrated.

A two-dimensional numerical model is developed to determine the role of soil in the formation of urban catchment runoff. The model is based on a modeling unit, called the Urban Hydrological Element (UHE), which corresponds to the cross-section of an urban cadastral parcel. Water flow in the soil of a UHE is explicitly simulated with a finite element code for solving the Richards' equation. Two runoff components, dependent on soil behavior, are represented: runoff from natural surfaces and drainage of groundwater into the rainwater network. In an initial case study, the model is applied to a 4.7-ha suburban catchment. Simulated and observed runoff and soil water pressure heads show reasonable agreement. Soil appears to play a significant role in the formation of runoff at the scale of the small catchment under examination: its contribution represents an average of 14% of the total per-event runoff volume. Soil contribution is particularly important during rainfall events characterized by a shallow water table level, which explains a determinant part of the seasonal trend of catchment response.