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Culvert inlet

Photograph showing culvert inlet and screen during a period of very dry weather.

Expert witness report on flooding
from culvert, southern England

Background

One of our senior staff acted as an expert witness in a case involving flooding from a small culverted watercourse in southern England. A blockage had formed in the culvert which resulted in extensive flooding to two properties during a period of high flows caused by melting snow combined with heavy rainfall.

Report

Our expert witness provided opinion on the obligations of the various parties, the speed of occurrence of the flooding, the reasonable steps which one of the parties could have taken prior to the flooding and the significance of several warning signs which occurred before the flood itself.

Engineering Calculations

To enable an opinion to be formed various engineering calculations were undertaken. These included estimating the peak flow from the culvert during the flood based on water levels observed by witnesses. The return period of the flood was then estimated by relating the calculated peak flow to a flood frequency curve derived by Flood Estimation Handbook methods. This showed that the flood was far more severe than would be suggested by the Met Office rainfall data alone. This information, together with estimated peak flows in the watercourse in the weeks prior to the flooding (due to both rainfall and also a burst water main) allowed the flood itself to be put into its proper context.

Also see our Expert Witness page.

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