Abstract
Abstract. Two of the most relevant components of any flood forecasting system, namely the rainfall-runoff and flood inundation models, increasingly benefit from the availability of spatially distributed Earth Observation data. With the advent of microwave remote sensing instruments and their all weather capabilities, new opportunities have emerged over the past decade for improved hydrologic and hydraulic model calibration and validation. However, the usefulness of remote sensing observations in coupled hydrologic and hydraulic models still requires further investigations. Radar remote sensing observations are readily available to provide information on flood extent. Moreover, the fusion of radar imagery and high precision digital elevation models allows estimating distributed water levels. With a view to further explore the potential offered by SAR images, this paper investigates the usefulness of remote sensing-derived water stages in a modelling sequence where the outputs of hydrologic models (rainfall-runoff models) serve as boundary condition of flood inundation models. The methodology consists in coupling a simplistic 3-parameter conceptual rainfall-runoff model with a 1-D flood inundation model. Remote sensing observations of flooded areas help to identify and subsequently correct apparent volume errors in the modelling chain. The updating of the soil moisture module of the hydrologic model is based on the comparison of water levels computed by the coupled hydrologic-hydraulic model with those estimated using remotely sensed flood extent. The potential of the proposed methodology is illustrated with data collected during a storm event on the Alzette River (Grand-Duchy of Luxembourg). The study contributes to assess the value of remote sensing data for evaluating the saturation status of a river basin.
Highlights
Over the last decade, many studies demonstrated that spatial information on the distributed physiogeographical characteristics and hydrologic responses of river basins can be gained from remote sensing observations
– a constant value of pre-event flow;
Once the sequence of models is calibrated using a well-documented flood event, only precipitation, a constant value of pre-event flow and flood extent are needed to provide flood forecasts
Summary
Many studies demonstrated that spatial information on the distributed physiogeographical characteristics and hydrologic responses of river basins can be gained from remote sensing observations. The list of Earth Observation-derived products that are potentially useful in watershed modelling is long, including, most notably, precipitation fields, land use maps, digital elevation models, maps of snow cover, soil moisture, flood extent, vegetation cover and evapotranspiration. Whereas some basin characteristics such as land use and topography can be retrieved from a limited amount of images, the temporal variations of soil moisture, flood extent and snow cover implicate that the corresponding data need to be provided at a daily or at least weekly basis in order to be routinely used in forecasting systems. In the same general context, Schumann et al (2007a) demonstrated the potential of Earth Observation data to understand
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