Avoiding Future Floods & Droughts
The management of rainfall has three central aims: when rain is plentiful it is to avoid flooding, when rain is in short supply to make sure the demands of people and the environment can still be met, and to assure water quality.
Given these three aspects of rainfall to manage, it is clearly anachronistic to manage them separately, particularly, if in doing so, improving one aspect worsens another; and yet in the UK that is exactly what we do.
With floods the main current preoccupation, understandably given the devastation these cause and their recent frequency, every effort is being made to make water-courses better conduits of surface water out to sea, whence it is lost from a demand and inland environment perspective; astonishingly, later desalination in times of need is seen as a cost-effective response.
Yet according to the latest report of the International Panel on Climate Change (IPCC), future droughts are the greater problem for the UK as population growth exacerbates predicted changes to rainfall patterns that will increase the propensity for both winter floods and summer droughts. Amongst the first to feel this effect will be farmers whose supplies for agriculture are already under stress in the drier South East of England; those stresses are predicted to intensify and spread north toward the Humber estuary within the next five years.
Under these circumstances, it might be anticipated that farmers would see a self-interest in collecting a sufficient amount of the water flowing across/alongside their land to provide them with an adequate supply for use during dry spells. This would, of course, have a favorable impact on down-stream flood risks, an impact that could formally act as flood-prevention attenuation given a little design ingenuity.
Exactly the same principle can apply in the urban environment by extending the existing SuDS principles to include water re-use as a requirement in the SuDS hierarchy (as illustrated). This principal has already been recognised by the Welsh Government and the Greater London Authority, both of which place water re-use as No-1 in the hierarchy; oddly, given the population density and relatively low rainfall in the South East, the same cannot be said of the rest of England which does not recognise water re-use in the SuDS context at all.
Getting back to first principles, it is pretty obvious that there is a strong correlation between managing rainfall to avoid floods, and managing rainfall to avoid droughts; this connection can only be made by managing both at the same time, in terms of national and planning policies. A good start could be made in that direction, by re-badging all departments, committees, and authorities with ‘flood’ in their names, by replacing the word ‘flood’ with ‘water.’
This editorial awas brought to you by the UK Rainwater Management Association, Partner at Flood Expo.