The recent debates and arguments about flooding on the Somerset Levels have been all about getting the floodwater off the levels, or using dredging to reduce the rate at which the waters rise once they reach them. The problem is, the present analysis completely ignores that:
- more water is falling, and
- more water is getting into the upper reaches of the rivers faster
To illustrate the first point, a paper by Tim Osborn and Douglas Maraun from the UEA’s Climate Research Unit reviewed the changing intensity of rainfall over Britain and concluded, in relation to winter rainfall,
River flooding, however, typically occurs after a number of days of heavy rainfall. To assess whether multi-day precipitation has changed, we counted how many days each winter fell at the end of a 5-day spell of “very wet” weather. Figure 3 shows that this has also increased, when averaged over the UK.
The second point is that none of the reporting and arguments about dealing with winter flooding on the Levels has yet to pay any significant attention to where all this run-off is coming from. The faster we drain the upper reaches of catchments, the more quickly larger volumes of water get down to the floodplains where they back up, because the main river cannot
be expected to get everything thrown at it out to sea very quickly. And, upstream there are the large, and growing, towns of Yeovil and Taunton, and upstream of Taunton, Wellington. New developments, housing and commercial, mean more hard surfaces and more hard surfaces means more water discharged directly into main rivers rather than soaking into the ground or being held back by vegetation.
As towns grow, and more ground gets paved, the situation will only get worse. SUDS – sustainable urban drainage systems
, must now be a priority for planners and urban managers in the Parrett catchment, simply to give the people who live and work on the Levels a chance to keep their feet dry in the winter.
Map from http://en.wikipedia.org/wiki/File:Map_of_Somerset_Levels.png