Post-flood field investigations in upland catchments after major flash floods: proposal of a methodology and illustrations

Post-event survey and investigation is one way to gain experience on natural hazards. The importance of the systematisation and standardisation of such investigations and re-analysis is progressively recognised in all the geophysical sciences as shown by the growing number of scientific papers and programs on the subject. But how to proceed in the case of a flash floods, what type of data should be collected for what type of analyses and to explore which particular issues? To give a first answer to these questions, a methodology for post-flash flood field investigations has been developed under the EC FLOODsite project and tested under the EC HYDRATE project. This paper presents shortly the principles of this methodology and illustrates its application for the study of two major flash floods that occurred in November 1999 and September 2002 in the South of France.