Traditional Indian johads, or small dams, have a great deal to teach us about protecting topsoil and preventing flooding, says Marc Stutter
An African proverb says it takes a whole village to raise a child. This holds true also that communities, rather than individuals, share responsibilities as custodians of the land across generations. So what’s that got to do with flooding in the UK? This month a group of UK researchers, policy-makers and land managers met in London to discuss new approaches for flood management. Their guest was an Indian villager known as the “Water Ghandi” for harnessing traditional water wisdom to restore drought-affected valleys in Rajasthan. The same small dams (termed johads) used in India to divert rainfall away from evaporation in the sun, deep into underground aquifers, are being trialled in the UK to help manage flooding. Furthermore the collective knowledge and ambition of Indian villagers provides lessons for the UK in how empowered local actions deliver positive results that cut through unclear messages across multiple policies. Building on several success stories, the UK initiative now seeks to prove how replicating small water holding structures across catchments provides an achievable and equitable way to further manage flood waters and bring wider environmental benefits.
If you ask people what they value soil for, then farmers and gardeners alike are likely to say: “to grow our food”. Few would highlight the role of soils in regulating the speed by which rain reaches our rivers. However, these two roles have historically been perceived as opposites. In many areas, past centuries of agriculture have straightened streams, drained and compacted soils and ploughed up and down slopes. These actions have reduced the landscape’s water holding capacity and exacerbated rapid flows that wash soil into streams and inundate floodplains. Yet, we should not forget that agriculture provides the vital provisioning service of food. Water experts are asking that society should value farming for water stewardship as well as food production.
The EU reform of the CAP necessitates that from 2015 landowners provide 5 per cent of arable and temporary grassland for ecological focus areas. Small water retention features could be integrated into the proposed fallow, buffers and field edges; however, the rules and funding to promote doing more than the minimum requirements remains unclear. The numerous possible designs of retention banks and ponds have a common aim to “slow, store, filter and disconnect” storm flows from fields thereby reducing flood peaks and minimising topsoil erosion. This approach of “soft engineering” uses local knowledge and materials (soil, wood, rock). Basic hydraulic principles are utilised to tune water outflows so structures temporarily retain water, both to protect crops and in readiness for further flood storage.
The vision is that land taken out of production can be designed to optimise water-related and other benefits for society and to make farms more resilient to future climate extremes. In return science and technology can help farmers develop ideas and applications to feed the world’s growing population. Improvements in crop breeding, pest, soil and nutrient management have the potential to reduce pesticide reliance, improve yields and crop quality. So, production could intensify sustainably on 95 per cent of the farmed landscape, whilst 5 per cent delivers a multi-functional landscape.
Annual costs of river flooding damage in Scotland have been estimated to exceed £30 million. Additionally, topsoil erosion can cost £40 per hectare annually, in terms of productivity losses, but also offsite impacts for habitats, water treatment and angling. Whilst hastening the flow of water from land by straightening streams and clearing ditches provides short-term localised benefits to some, it conveys problems downstream. Alternatively collective actions to slow, store, filter and disconnect water conceptually brings a catchment-scale solution. The further up the catchment these measures are placed the better; slow the flow before it gains energy.
For smaller flood events success is likely. However measures in upper catchments should accompany, not replace, the ultimate protection of engineered schemes at vulnerable sites on bigger rivers. They are not the silver bullet, but are attractive due to simplicity, low cost and wider benefits. As we enter the winter period it seems inevitable that somewhere communities will suffer the misery of flooding from a river. Proactive local-led interventions allow communities a shared contribution to actions to ease flooding without waiting for national prioritisation in larger schemes.
• Dr Marc Stutter is leader of the managing catchments and coasts research theme at the James Hutton Institute. The institute tackles flood-related challenges with Catchment Partnerships, Newcastle University and internationally through the Flow Partnership. For more information visit www.hutton.ac.uk/mcc