Hervé Andrieu

Parameterization of the urban water budget with the submesoscale soil model

Abstract 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-Modelisation du Bilan Hydrique (HAPEX-MOBILHY) and the European Field Experiment in a Desertification Threatened Area (EFEDA). The SM2-U water budge...

Evaluation of Methods for Representing Urban Terrain in Storm-Water Modeling

Many stormwater modeling problems consider watersheds comprised of complex flow networks including surfaces, streets, pipes, and channels. Ideally, hydrologic methods would be used to model the accumulation of runoff on surfaces while hydraulic methods would be used to explicitly model the flow in each street, pipe, and channel. In many practical circum- stances, however, only the largest pipes and channels are explicitly modeled with hydraulic methods. Thus, most subcatchments include numerous streets and small pipes that can affect the accumulation and movement of water. Digital Elevation Models (DEMs) are widely used to determine geometric characteristics of these subcatchments, but street gutters and pipes are not resolved in such data. To overcome this problem, known streets and pipes are often burned into the surface by reducing the local elevations by a specified amount before calculating flow paths and the associated subcatchment characteristics. In this paper, existing and proposed methods for including these conduits into DEM surfaces are evaluated. The results suggest that the derived characteristics are sensitive to the selected method. We also find that a new method, which makes use of known pipe elevations, is most successful at reproducing realistic flow paths. Finally, we find that errors in the implied watershed characteristics are difficult to over- come by calibration of other model parameters.