Emmanuel Berthier

The study of two stretches of street during 38 months has been performed to analyze the hydrological behavior of streets during rain events. The results show that runoff coefficients are very variable and runoff losses may be important. In order to better understand this behavior, a physically based model has been used. This model, BiL, combines a porous media flow module with a surface runoff module. The lateral runoff transfer in the lateral gutter is approximated by the Muskingum model. Evaporation is simulated by an adaptation of the Penman method. A sensitivity study shows that the model is mainly sensitive to saturated hydraulic conductivity of the asphalt pavement and to the storage capacity. The comparison of simulated and observed data gives good results for the runoff outflow at a 3 minutes time step. Nevertheless, the simulation results are less encouraging for the runoff coefficient. This study of the water budget of two street stretches during a time period of 38 months indicates that the infiltration and evaporation represent between 20 and 30% of rain.

Development in sustainable stormwater management in cities needs adapted modelling tools, which can consider urban water cycle in an integrated manner, by modelling hydrological fluxes as well as hydric state of the urban soil. The latter become particularly important when stormwater is handled with innovative point of view treating the resource or/and climatic aspects of rainwater. Yet circulations of rainwater within urban areas are complex and are not described in a detailed manner. Integrated urban hydrological models keep on being updated. This paper presents our work as a contribution to the development of such a model. A saturation module has been implemented to the integrated model URBS. The new model runs continuously at a short time step over long periods. Model evaluation is based on its capacity to reproduce saturation level and runoff measurements. This study shows the importance of modelling groundwater movement that is highly influenced by buried sewer networks. This ...

Extensive green roof technique (EGR) is becoming increasingly used for sustainlable rainwater management, but tools to properly design it need still development. The work presented herein is a first step to build a simple and robust model of green roof hydrological behavior, in order to be used to assist in the stage of EGR design. The type of model tested (reservoir model with the force-restore scheme in the substrate) appears suitable to reproduce the hydrological behavior of a 146m 2 EGR during one year. An original and relevant method was used to study the sensitivity and the calibration of the model. Such model allows also to access important information, like the variation of storage water capacity in the EGR, key variable for runoff retention and regulation.

While the need for on-site stormwater and pollution control is generally well accepted by both scientists and practitioners, there is no real agreement yet on management or design criteria to be given to developers for implementation of most suitable runoff control practices. Hydrologic criteria, directly related to stormwater facility’s sizing, may for instance usually either be expressed as flow-rate or volume targets. Although these criteria are usually assumed to provide adequate runoff and pollution control, their comparison has only received scant attention and determining optimal values for both volume and flow-rate targets probably remains difficult for most practitioners. The methodology presented here therefore aims to investigate the suitability of different flow-rate and volume-based stormwater management options for on-site pollution control. Flow-rate control and runoff volume reduction strategies have been simulated (over a 15-year period) with a relatively simple con...

Les flux de polluants associés aux eaux pluviales urbaines sont un facteur majeur de dégradation des milieux aquatiques superficiels dont la gestion est devenue un réel enjeu écologique au cours des dernières décennies. De nombreuses solutions techniques ont ainsi été développées afin de limiter la formation du ruissellement à l'amont des bassins versants urbains. Néanmoins, alors que la plupart des pays ou collectivités aspirent à la maîtrise de cette pollution, les réglementations ou prescriptions données aux opérationnels demeurent assez hétérogènes. L'objectif de cet article est donc, en se basant sur une synthèse bibliographique à l'international des pratiques de gestion des eaux pluviales, d'analyser les différents critères pouvant être donnés aux aménageurs en considérant à la fois leur pertinence pour la maîtrise des flux de polluants et les implications de leur définition en termes de choix ou de dimensionnement des techniques alternatives. Alors que les cri...

Environmental issues and urban areas growth focus the interest on urban catchment runoff. Urban runoff is mainly generated by runoff over impervious surfaces (i.e., road, roof or parking). Different studies have shown that urban surfaces display an hydrological behaviour including several processes as interception, infiltration and evaporation. Our objective is to describe the different water budget components, of an asphalt

Over the last decade, a growing interest has been shown toward innovative stormwater management practices, breaking away from conventional "end of pipe" approaches (based on conveying water offsite to centralized detention facilities). Innovative strategies, referred to as sustainable urban drainage systems, low impact development (LID) or green infrastructures, advocating for management of runoff as close to its origin as possible, have therefore gained a lot of popularity among practitioners and public authorities. However, while the need for pollution control is generally well accepted, there is no wide agreement about management criteria to be given to developers. This article hence aims to compare these criteria through literature analysis of different state or local stormwater management manuals or guidelines, investigating both their suitability for pollution control and their influence on best management practices selection and design. Four categories of criteria w...

The study of two stretches of street during 38 months has been performed to analyze the hydrological behavior of streets during rain events. The results show that runoff coefficients are very variable and runoff losses may be important. In order to better understand this behavior, a physically based model has been used. This model, BiL, combines a porous media flow module with a surface runoff module. The lateral runoff transfer in the lateral gutter is approximated by the Muskingum model. Evaporation is simulated by an adaptation of the Penman method. A sensitivity study shows that the model is mainly sensitive to saturated hydraulic conductivity of the asphalt pavement and to the storage capacity. The comparison of simulated and observed data gives good results for the runoff outflow at a 3 minutes time step. Nevertheless, the simulation results are less encouraging for the runoff coefficient. This study of the water budget of two street stretches during a time period of 38 months indicates that the infiltration and evaporation represent between 20 and 30% of rain.

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

Analysis of experimental runoff coefficients on urban catchments has shown that the hydrological response of such catchments varies from one rainfall event to the next and depends on rainfall characteristics and initial water state. This variability cannot be totally reproduced by classical urban models (initial loss and constant runoff coefficient model for example). Moreover several studies have highligted the importance

ABSTRACT 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.

The urban water budget encompasses different terms, including precipitation, evap- otranspiration, water storage in the soil and runoff in the urban Rainwater Drainage Network (RDN). These terms interact with each other: for instance, runoff generation in the RDN during a rainfall event depends on the importance of the evapotranspiration process during the dry period before the event. Better ascertain the hydrological im- portance of each processes of the urban water budget should lead to an improvement of rainfall - runoff modelling of moderate rain events, which is necessary to reduce the pollution caused by urban runoff. This communication deals with the urban fluxes at the soil - atmosphere interface and focuses on the evapotranspiration process. Two models are run on a small suburban catchment, on a continuous basis and over a five- year period. Both models are based on a modelling unit representing the cross-section of an urban parcel at the cadastral scale. The unit size is well adapted to the in-depth and physically based simulation of the evapotranspiration taking place above the var- ious types of urban surfaces. SM2-U is the urban soil model of a calculation code performing high resolution simulations of urban atmosphere ; it describes the atmo- spheric processes in detail. The Urban Hydrological Element (EHU) simulates the role of soil in the runoff formation in the RDN, it specifies water flow paths in the urban soil with the help of a finite element code. The results of both models show similar- ities but also significant differences: above the catchment studied, evapotranspiration at a yearly time step represents 66% of the precipitation with the UHE model, but is only 32% with the atmospheric model SM2-U. The difference in the calculation of the evapotranspiration above natural surfaces accounts for the difference in the results of both models. These results of simulation now require a validation using data from an urban area.