The UBL/CLU (urban boundary layer/couche limite urbaine) observation and modelling campaign is a side-project of the regional photochemistry campaign ESCOMPTE. UBL/CLU focuses on the dynamics and thermodynamics of the urban boundary layer of Marseille, on the Mediterranean coast of France. The objective of UBL/CLU is to document the four-dimensional structure of the urban boundary layer and its relation to the heat and moisture exchanges between the urban canopy and the atmosphere during periods of low wind conditions, from June 4 to July 16, 2001. The project took advantage of the comprehensive observational set-up of the ESCOMPTE campaign over the Berre-Marseille area, especially the ground-based remote sensing, airborne measurements, and the intensive documentation of the regional meteorology. Additional instrumentation was installed as part of UBL/CLU. Analysis objectives focus on (i) validation of several energy balance computational schemes such as LUMPS, TEB and SM2-U, (ii) ground truth and urban canopy signatures suitable for the estimation of urban albedos and aerodynamic surface temperatures from satellite data, (iii) high resolution mapping of urban land cover, land-use and aerodynamic parameters used in UBL models, and (iv) testing the ability of high resolution atmospheric models to simulate the structure of the UBL during land and sea breezes, and the related transport and diffusion of pollutants over different districts of the city. This paper presents initial results from such analyses and details of the overall experimental set-up.Ã

International audienceIn this paper we explore several indicators to evidence the impact of land use change, and particularly of urbanization/artificialization on discharge series of periurban catchments. A first set of indicators is derived from the literature and describes the monthly and annual hydrological regime, low flows and high flows, and flow components. Statistical tests are also applied to assess the existence of trends/rup-tures on the longest time series. In addition, new indicators, especially built to show the impact of sewer overflow devices (SODs) and infiltration into sewer networks are proposed. The method is applied to the Yzeron (150 km 2) catchment, located close to Lyon city (France) where various discharge gauges with a variable time step are available on sub-catchments ranging from a few to 130 km 2 (some of them nested), with a large variety of land uses (forest, agricultural land, artificialized areas). In addition, discharge is also measured in a SOD and a combined sewer network so that the relevance of the new proposed indicators can be assessed. In the largest sub-catchments, the results show a decrease of specific discharge from upstream to downstream corresponding to an increase of artificialized areas, except for high flows. When a SOD is present, the specific discharge is increased for frequencies larger than 50%, and the frequency of zero daily discharge is decreased. Waste water can be the only source of water in autumn month in a 4.1 km 2 sub-catchment. Base flow is also decreased for the most urbanized catchments. Our results confirm the impact of SODs on the modification of the flood regime, with an increase of frequent floods, but a marginal impact on the largest floods, mainly governed by saturation of the rural parts of the catchments. The decomposition of the sewer discharge shows that, on an annual basis, infiltration in the sewer network accounts for 30% of the total discharge and runoff due to rainwater to about 40% (the remaining being composed of the waste water discharge). It can explain the decrease of base flow. Our analysis shows that, for periurban catchments, a long term monitoring of nested sub-catchments and infrastructures (SODs, sewer networks) with a small time step, is very valuable and provides data allowing a quantitative assessment of the impact of urbanization on the whole hydrological regime

International audienceThe hydraulic properties of the topsoil control the partition of rainfall into infiltration and runoff at the soil surface. They must be characterized for distributed hydrological modelling. This study presents the results of a field campaign documenting topsoil hydraulic properties in a small French suburban catchment (7 km2) located near Lyon, France. Two types of infiltration tests were performed: single ring infiltration tests under positive head and tension-disk infiltration using a mini-disk. Both categories were processed using the BEST--Beerkan Estimation of Soil Transfer parameters--method to derive parameters describing the retention and hydraulic conductivity curves. Dry bulk density and particle size data were also sampled. Almost all the topsoils were found to belong to the sandy loam soil class. No significant differences in hydraulic properties were found in terms of pedologic units, but the results showed a high impact of land use on these properties. The lowest dry bulk density values were obtained in forested soils with the highest organic matter content. Permanent pasture soils showed intermediate values, whereas the highest values were encountered in cultivated lands. For saturated hydraulic conductivity, the highest values were found in broad-leaved forests and small woods. The complementary use of tension-disk and positive head infiltration tests highlighted a sharp increase of hydraulic conductivity between near saturation and saturated conditions, attributed to macroporosity effect. The ratio of median saturated hydraulic conductivity to median hydraulic conductivity at a pressure of − 20 mm of water was about 50. The study suggests that soil texture, such as used in most pedo-transfer functions, might not be sufficient to properly map the variability of soil hydraulic properties. Land use information should be considered in the parameterizations of topsoil within hydrological models to better represent in situ conditions, as illustrated in the paper. Copyright © 2010 John Wiley & Sons, Ltd