3b42 flood modelling part 02

The extensive flood damages sustained worldwide cost approximately 20 billions £ a year. These natural catastrophes have a certain level of predictability allowing preparedness, mitigation and defences. The key to minimizing the damages lies in the precision of the prediction of the flood extent and dynamic.

The present study explores the error propagation from satellite rainfall estimates into the modelling of the flood plain extent in the Semois basin (Belgium). The area near Villers-sur-Semois (49.69° Lat N, 5.56° Long E , 5.8 ha ) has been modelled with a 1D2D software suites (ISIS free) forced with discharge inputs from 3 different sources : the observed gauged flow, the simulated flow based on rain gauges data and the simulated flow based on the 3b42 v6. multi-satellite product of the Tropical Rain Monitoring Mission (TRMM) providing a rainfall rate every 3hours for a cell size of 0.25 deg. Rain were transformed into discharge with the revitalised FSR/FEH rainfall-runoff method which is part the Flood Estimation Handbook in UK.

The flood plain based on the 3b42 data appears grossly overestimated (135% of the observed flow flood extent) or underestimated (50%) depending on the event chosen, clearly dismissing the adequacy of the dataset. The flood plain modelled with the observed discharge and the one modelled based on the rain gauge data appear quite similar in their maximum extent but present a different temporal dynamic. They present a good similarity with the flood risk map prepared by the regional authorities.

The modelled flow based on the rain gauges has a Nash Sutcliffe coefficient of efficiency between 0.23.and 0.33 according to the event modelled.

Category:

Science & Technology

Tags:

• 3b42
• flood
• modelling
• modeling
• Albert
• Grela
• Semois
• ISIS
• ReFH
• inundation