The challenge of forecasting impacts of flash floods: test of a simplified hydraulic approach and validation based on insurance claim data
Up to now, flash flood monitoring and forecasting systems, based on rainfall radar measurements and distributed rainfall–runoff models, generally aimed at estimating flood magnitudes – typically discharges or return periods – at selected river cross sections. The approach presented here goes one...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-11-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/21/5911/2017/hess-21-5911-2017.pdf |
| Summary: | Up to now, flash flood monitoring and forecasting systems, based on rainfall
radar measurements and distributed rainfall–runoff models, generally aimed at
estimating flood magnitudes – typically discharges or return periods – at
selected river cross sections. The approach presented here goes one step
further by proposing an integrated forecasting chain for the direct assessment
of flash flood possible impacts on inhabited areas (number of buildings at
risk in the presented case studies). The proposed approach includes, in
addition to a distributed rainfall–runoff model, an automatic hydraulic
method suited for the computation of flood extent maps on a dense river
network and over large territories. The resulting catalogue of flood extent
maps is then combined with land use data to build a flood impact curve for
each considered river reach, i.e. the number of inundated buildings versus
discharge. These curves are finally used to compute estimated impacts based
on forecasted discharges. The approach has been extensively tested in the
regions of Alès and Draguignan, located in the south of France, where well-documented major flash floods recently occurred. The article presents two
types of validation results. First, the automatically computed flood extent
maps and corresponding water levels are tested against rating curves at
available river gauging stations as well as against local reference or
observed flood extent maps. Second, a rich and comprehensive insurance claim
database is used to evaluate the relevance of the estimated impacts for some
recent major floods. |
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| ISSN: | 1027-5606 1607-7938 |