Can only Westminster afford the best flood protection?
Nigel Williams, 19 June 2014
The Environment, Food and Rural Affairs (EFRA) committee has reported on the flooding in the Somerset Levels and elsewhere. Severe weather and high tides led to “widespread flooding from the sea, rivers, groundwater and surface water”. They found that unprecedented rainfall coincided with a reduction in drainage budgets. Their conclusion began:
“The unpredictable nature of climate change creates an inherent uncertainty about the exact nature of flooding risk in the future, but there is consensus that flooding risk will increase.”
The precise nature and location of the risk may be difficult to predict, but the 2012 IPCC report described the outlines clearly:
“It is likely that the frequency of heavy precipitation or the proportion of total rainfall from heavy falls will increase in the 21st century over many areas of the globe. This is particularly the case in the high latitudes and tropical regions, and in winter in the northern mid-latitudes.”
We were warned.
A major area of concern was the diversion of budgets away from dredging. Standing water on Somerset farmland remained there too long for the crops beneath to survive. Providing the water with an efficient route out to sea appears critical to mitigating the disaster. As the EFRA report acknowledges, the situation is more complicated. We are dependent on the expertise in the Environment Agency and elsewhere to understand how best to deploy flood defences. For example, much of the Somerset Levels is below sea level. As Keith Beven, Professor of Hydrology at Lancaster, explains, dredging would also allow tidal water further up the river before it met with flooding rainwater coming down. Faced with increased extreme rainfall and rising sea levels, even methods that have traditionally been effective will be severely tested.
London is fortunate. It has the Thames Barrier, a masterpiece of engineering installed in the early eighties. Although designed to cope with the threat at the time of occasionally storm surge and slowly rising sea levels, it has also served as a defence against heavy rainfall. By raising the barrier before high tide, the Thames basin could be kept at perpetual low tide. The accumulated rainfall was still more than the banks of the Thames could hold but central London was spared the worst effects and there was an outlet at least for some of the water. The graph’s brown bars show have rapidly action against fluvial flooding has grown since the barrier was first deployed.
Superstorm Sandy hit New York in November 2012 and several subway stations were inundated. The winter storms hit the UK in 2013/14. They took out the railway in Dawlish and damaged sea defences in Rhyl, Aberystwyth and elsewhere. The Thames Barrier protected London throughout.
The EFRA committee commended efforts made for flood relief and called for funding to improve resilience to future flooding events. Giving everybody the same protection as Westminster could be a very expensive business.