HESS Hydrology and Earth System Sciences HESS Hydrol. Earth Syst. Sci. 1607-7938 Copernicus Publications Göttingen, Germany 10.5194/hess-15-3555-2011 Correction of upstream flow and hydraulic state with data assimilation in the context of flood forecasting Ricci S. 1 Piacentini A. 1 Thual O. 1 2 Le Pape E. 3 Jonville G. 4 URA, CERFACS-CNRS, URA1875, Toulouse, 42, Avenue Gaspard Coriolis, 31057 Toulouse Cedex 01, France INPT, CNRS, IMFT, Allée Camille Soula, 31400, Toulouse, France SCHAPI, Toulouse, 42, Avenue Gaspard Coriolis, 31057 Toulouse Cedex 01, France CERFACS, Toulouse, 42, Avenue Gaspard Coriolis, 31057 Toulouse Cedex 01, France 23 11 2011 15 11 3555 3575 Copyright: © 2011 S. Ricci et al. 2011 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://hess.copernicus.org/articles/15/3555/2011/hess-15-3555-2011.html The full text article is available as a PDF file from https://hess.copernicus.org/articles/15/3555/2011/hess-15-3555-2011.pdf

The present study describes the assimilation of river water level observations and the resulting improvement in flood forecasting. The Kalman Filter algorithm was built on top of a one-dimensional hydraulic model which describes the Saint-Venant equations. The assimilation algorithm folds in two steps: the first one was based on the assumption that the upstream flow can be adjusted using a three-parameter correction; the second one consisted of directly correcting the hydraulic state. This procedure was applied using a four-day sliding window over the flood event. The background error covariances for water level and discharge were represented with anisotropic correlation functions where the correlation length upstream of the observation points is larger than the correlation length downstream of the observation points. This approach was motivated by the implementation of a Kalman Filter algorithm on top of a diffusive flood wave propagation model. The study was carried out on the Adour and the Marne Vallage (France) catchments. The correction of the upstream flow as well as the control of the hydraulic state during the flood event leads to a significant improvement in the water level and discharge in both analysis and forecast modes.

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