1. Professor, Bordeaux Institute of Mathematics, CNRS UMR 5251, Bordeaux I Univ., 33405 Talence, France.
2. Project Manager, Safege Company, Parc de l’Ile-15/27 rue du Port-92022 Nanterre Cedex, France.
3. Associate Professor, Bordeaux Institute of Mathematics, CNRS UMR 5251 and INRIA Sud-Ouest Projet MC2, Bordeaux I Univ., 33405 Talence, France (corresponding author).
4. Research Scientist, Hydraulics and Civil Engineering Research Unit, Cemagref, 50 Ave. de Verdun, Gazinet, F-33612 Cestas Cedex, France.