Flood management in areas currently at risk

We found that flooding increases most in places where risk is already high now“.

North Dairy FarmNo sustainable drainage system is planned by the developer for the area covered by impermeable solar panels.

The Flood Extent Map shows the North Dairy Farm Site surrounded by Flood Zones 2. and 3. and bisected by the Short Wood Brook through the centre of the site. This landscape has been shaped by high levels of rainfall (< 1000 mm a year – three times more than south Dorset) and the myriad of waterways fed by the rapid discharge of rainfall (50% runoff) from the Downs and escarpments, into the Catchment Areas of the Upper Lyddon and Wonston Brook. The proposed site is saturated for 200 days a year and the two catchments meet just 90 metres to the north of the proposed Site.

Now new research modelling and findings by the School of Geographical Sciences, University of Bristol and Fathom – a company that assesses flood and climate risk – have simulated all types of flooding in the coming decades. They used information about terrain, river flow, rainfall patterns and sea level to build a detailed picture of how much flood damage there would be to people’s homes and businesses across England, Scotland and Wales.

Flooding is the principal environmental hazard identified in the UK’s National Risk Register (Cabinet Office, 2020), and the past 25 major events have resulted in substantial economic damage and loss of life. The analysis contains a greater level of detail and nuance compared to previous work and represents our current best understanding of the UK’s changing flood risk landscape.

The road to Hazelbury Bryan flooded – within metres of the proposed site.

“We found that flooding increases most in places where risk is already high now, so the best thing we can do to prepare for the impact of climate change is to strengthen flood management in currently at-risk areas, and this will bring immediate economic and social benefits as well.”

The modelled estimates of historical flood risk, which are based on actual river flow, rainfall, and tide-surge observations as well as climate model projections, match well with data on flood losses from the Association of British Insurers and shed new light on the financial toll of flooding. Previous studies by other research groups have already shown that historical U.K. economic losses due to flooding were three times less than the Government’s estimates, but this is the first time the observed losses have been replicated and corroborated by a computer model.

Co-author Dr. Oliver Wing, Chief Research Officer at Fathom and Honorary Research Fellow at the University of Bristol, said, “This study, which harnesses new data and the very latest modelling techniques, validates Fathom’s U.K. Flood Map and has given a new level of insight into the impact of climate change on flooding in future.
“The modelling provides clear evidence that flood risk needs to be a bigger international priority and that current governance doesn’t go far enough.

The UK lies under the westerly track of mid-Atlantic storm systems including 35 extratropical cyclones. On making landfall, these storm systems encounter extensive upland areas to the west of the country resulting in orographic enhancement of precipitation. This subsequently falls onto river catchments that are (in global terms at least) relatively short and steep and therefore prone to flooding (Black and Law, 2004; Luca et al., 2017). Convective rainfall activity in summer can be intense (Chan et al., 2016) and may lead to flash flooding in small catchments (Archer and Fowler, 2021) such as the Upper Lydden and Wonston Brook catchments.

Here is an extract of the research paper.

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