Taking a hard look at soft defences against Britain's floodwaters
The humble earthworm may help to ease Britain’s increasing flood risk
Something interesting is happening just under ground in Loddington in Leicestershire, where the Game and Wildlife Conservation Trust has for years investigated ways in which man and nature can live more in harmony.
Elsewhere in Britain, thousands of homeowners have begun the new year miserably, coping with the damage cause by December’s flooding and fearful that the high waters are harbingers of ever more frequent disasters.
Hundreds of millions of pounds have been spent on flood defences, often successfully, if expensively. In some places, though, the defences failed to hold back the waters, while locals in other villages and towns fear defences in one place merely pushes the problem further downstream.
The Allerton Project in Loddington may have part of the solution, where it is researching the impact of farmers abandoning time-honoured traditions of ploughing and, instead, moving to drill tillage plants into the soil.
The change – already regarded as normal practice among half of British farmers – has significant effects. “It reduces the impact of rain on soil as it hits and helps the earthworm numbers to build up,” says the trust’s Alastair Leake.
Earthworms “don’t like being ploughed very much”, he says, adding that where the soil is left to itself their numbers increase by 20-fold in just a few years with dramatic improvements, too, in the soil’s ability to absorb water.
“They particularly like the trash on the surface, bits of chopped straw. They will pull this straw together into little piles called middens and they pull this down into the soil and create a really porous structure.”
Last month, the British Meteorological Office raised eyebrows when it said that last year was not the wettest yet experienced in Britain.
Accepting that it was the wettest year on record in England, the Met Office said it was third wettest for Wales, just the 17th for Scotland, while Northern Ireland enjoyed – or suffered – just its 40th wettest 12 months.
In the parish of Loddington and Launde, Allerton’s farm manager Phil Jarvis has kept his own records over 20 years. These show that rainfall there in 2012 was 1,036mm, far ahead of the previous record of 859mm recorded in 2000.
Leake says the Met Office figures do not point out that the rain fell in a shorter period of time – the first four months were dry. “We did have an average year, but the rain was squeezed in in the rest of the year.”
However, the flooding in most places is caused by just a 10 per cent rise in the peak-flow of many rivers, according to the Environment Agency. If water can be held up on farmland, thus arriving in rivers over a longer period of time, then disasters can be averted.
In Northumbria, some simple but rather effective measures have been put in place in Belford, which has been plagued by flooding since 1877. Five crises between 2007 and 2009 decimated the town’s shopkeepers.
So-called “soft defences”, rather than expensive water-barriers, have been created, where farmers have co-operated with the environment agency to create temporary ponds on the edges of fields to store water. Woodland planting has helped, too.
Zig-zag patterned wooden dams slow the passage of water in drains, trapping sediment, but also offering a boon to newts and frogs, while even a beaver dam is playing its role in slowing nature’s fury as it hurtles towards the Northumbrian town.
In some places, bands of willow, known as “willow hurdles”, have been laid across the flood-plain to offer roughness to the landscape, doubling the time that it takes for water to travel downstream.
In Cumbria, the Newton Rigg Agricultural College is encouraging local farmers to use grassland aerators attached to the back of a tractor to create small holes by punching through the turf on compacted farmland. Such measures benefit neighbours because the water becomes more of a sponge but, the college says, it also benefits the farmers because the land stays drier and is accessible by machinery for longer.
The Loddington and Belford experiments offer a template for the future, where an increasingly cash-strapped Whitehall will be unable to meet ever-growing demands from flood-risk towns for protection.
Total rainfall may not increase significantly in Britain over the next 30 years, but there seems little doubt, scientists say, that it will become ever more concentrated into torrential downpours during winter months.
Nevertheless, the department of environment, food and rural affairs remains agnostic, but willing to be convinced about the measures, pointing that evidence that “soft” defences have local benefits is strong, but less so for a full river catchment.