Estimation of catchment flood potential using satellite data
A project was undertaken to develop a system to predict the probability of a flood
occurring on a particular river catchment as a result of convective storm rainfall, The
system is designed for use in developing countries and uses data from the Advanced
Very High Resolution Radiometers (AVHRR) aboard the NOAA polar orbiters and
the synthetic aperture radar (SAR) of the ESA ERS satellites.
The system uses data from the SAR to determine soil moisture content (SMC). From
observed differences in SMC it is possible to estimate the evapotranspiration at the
surface.I n combination with AVHRR derived net radiation, the evapotranspiration,in
turn, is used to calculate the sensible heat flux. The sensible heat flux is used in a
simple convective model to estimate the height of the atmospheric boundary layer and
the velocity of an ascending parcel of air. From this the probability of convective
storm occurrence and maximum rainfall is calculated. By inputting the rainfall into a
simple, lumped hydrological model the flood potential is found.
The system has been tested on two catchments: The River Irwell in Northwest
England and the Kafue River in Zambia with good results. Investigations have been
made into the advantages of combining the satellite-derived fields with those
produced by numerical weather prediction models and some aspects of the system are
observed to benefit from this approach.