AN ABSENCE of historical flood data in short steep catchments is preventing extreme events like last year's Boscastle floods from being modelled accurately, a leading hydrology expert has warned.
Frank Farquharson, head of water resources at the Centre for Ecology & Hydrology (CEH), urged the Environment Agency to measure high river flows in the south west to help analyse flooding events.
The current standard for modelling floods uses river flow data and catchment characteristics taken from the Flood Estimation Handbook (FEH), developed by CEH.
'But there aren't any similar small catchments like Boscastle being monitored by the gauging authorities, ' said Farquharson.
'The 1,000 odd flood gauging stations are only in large rivers like the Thames and Severn.'
He urged gauging authorities such as the Environment Agency to measure flooding in key rivers which had suffered flash floods, like the Valency in Boscastle and East and West Lyn in North Devon.
Farquharson's warning came after the Agency revealed that the current FEH modelling of the Boscastle event did not marry up with peak flows recorded in photographs.
Agency flood defence manager Gordon Trapmore also spoke on the subject last week.
'The FEH approach shows peak flows occurring much later than they actually did. We've recreated the event as best we can, but we can't mirror exactly when points [on the river] became blocked, ' he said.
Trapmore was speaking at an ICE conference in Launceston on the Boscastle floods.
He agreed that more data from short, steep catchments was needed, but warned that it would be expensive to monitor.
He added that there would be difficulty in mobilising Agency staff in time to verify peak flows in flash floods.