September 19, 2014

Hydrological risks

Over the last twenty years, flooding has occurred repeatedly in all industrial countries. More than 50% of all natural disasters throughout the world are caused by flooding, i.e. 20,000 deaths per year on average. In France, out of 160,000 km of rivers and streams, a surface of 22,000 km² is acknowledged to be particularly subject to flooding, distributed over 7600 towns and representing a population of 2 million shoreline residents.

In terms of hazard assessment, surveillance, prediction and prevention and the management of hydrological risks, the information supplied by the Pleiades data will be useful in several ways:

  • at prevention level:
    • when the risk map is drawn up, by assessing soil vulnerability and providing information on land use and the surface condition,
    • by plotting altitudes (and slopes: DTM) and by mapping flows.

  • at prediction level:
    • by information on land use (which "strengthens" the run-off coefficient assessments),
    • by detecting rises in water level in reservoirs and dams,
    • by drawing up maps of soil moisture,
    • by drawing up early indicators of deterioration or risks of flooding (changes in land use or morphology)

  • at crisis management level by knowledge of the extent of flooded areas in real time,

  • and at post-crisis management level by assessing the damage and the geographical extent (maximum if possible) of the floods, and a damage report and inventory.