Floods – the FHT position
19th February 2014
It’s been one of the wettest winters in southern England for 100 years.
So what does this mean for our freshwater ecosystems, and what should we be doing about flood management?
We’ve joined with other environmental NGOs and CIWEM, the Chartered Institution of Water and Environmental Management, to put forward our views, which you can read here and read the CIWEM report here:
Over the last few years we’ve also been doing something ourselves – especially heading-up a range of applied research projects investigating the effects of land management on freshwaters, work which guides our practical programmes. Now we’re working on the Water Friendly Farming project with the Game & Wildlife Conservation Trust where we are experimenting with different ways of reducing pollution and holding back water at the top of the catchment to improve freshwater habitats.
But with freshwater habitats already badly degraded we need to be careful not to damage the water environment even more by our response to the floods.
So as well as assessing the benefits for people of different flood management options we also need to think realistically about how this will help to protect freshwaters.
At the moment there’s a danger of exaggerating the benefits of some of the solutions.
Popular amongst environmental groups, and some official bodies, has been the call to hold back the water in the catchment, planting trees (which can intercept water before it even reaches the ground, and help it soak in as well) and digging ponds to store water temporarily.
At a small geographic scale – a few square kilometres – there are some promising positive effects (e.g. Pontbren – which the Guardian referred to, and Belton, which the BBC referred to), but so far nobody knows whether these will work on a large scale – the kind of scale that would stop flooding in Oxford, or Worcester, or Windsor. To find out whether it can really make a difference we’ll need to be much more ambitious in our practical work, and also greatly improve our computer models, to have a chance of proving just how much contribution this approach can make.
Some have called for beavers: it’ll be lovely having beavers around but the volumes of water they can store behind dams are comparatively tiny (and remember, a lot of the water behind those dams will be polluted; the beavers might help clean up a bit but still is that we really want them for, to clean up our pollution?). One quote recently suggested that a 3 ha beaver enclosure was holding back 400 cubic metres of water. There’s about that much water going down the Thames through Staines every second at present, so to hold a week’s worth of Thames water a very rough calculation suggests you’d need about 18,000 square km of land completely given over to beavers – just for the Thames. That’s about 10 times the area of Greater London.
The problem is that water is complicated: it matters both how much there is and how clean it is. And just as we need to take stock of managing the amounts of water, we also need to take a good look at the pollution caused. There’s just as much polluted water out there as before the rains began: perhaps now even more as dirty brown water pours off of farmland, roads and out of sewage works. Less than a quarter of rivers are in Good condition ecologically, and only 1 in 10 ponds is biologically healthy, much of this due to pollution (and not to either a shortage or overabundance of water).
So what is Freshwater Habitats Trusts five point plan?
1. Collect the information we need to make good choices – sounds very dull, but it’s the only way to make good decisions. In particular we need to test how much difference land management measures can make to flood control and pollution at a catchment scale. For example, what benefit will there be in putting back natural bends in rivers: so far, research world-wide has been disappointing, with few biological benefits apparent from this measure; we’ll need to be more successful to make a difference to holding water back.
2. Find out which bits of the water environment are most important for freshwater life – surprisingly we don’t know this already. With partners we’re starting to get this information together. It’s vital we know where we can have the most positive effect for biodiversity whilst we’re trying to fix the flooding problem.
3. With the overwhelming need to prevent damage to land and property, its more important than ever to protect the best freshwaters from unintentional damage – for example from dredging.
4. As well as controlling floods we need to think at the same time about pollution because the two often go together. Pollution blights an unbelievably large amount of the freshwater environment, and floods are almost certainly making this worse, from the tiniest headwaters to the biggest lakes.
5. Manage the land to reduce runoff to natural levels and hold back more water – but be realistic. During the biggest floods we probably won’t be able to hold back all the water and it will be vital to make our environment – human and natural – more resilient to floods.