Author Fran Southgate
I’m sure that you have all noticed that the gigantic puddles and floods are back following some particularly heavy rainstorms last week. As the wetland officer for Sussex, I am always trying to remind people that the swathes of countryside that they see underwater are storing the water from these rainstorms for us, helping enormously to keep it out of our homes and businesses. But what I learnt this week about the contribution that good soil can make to reducing flooding surprised even me.
A soil with only 1% organic matter in it, can hold up to 170 000 litres of water per hectare. When you multiply that up to the area of Sussex (around 400 000 hectares), and add in the fact that many soils have up to 10% organic matter in them, suddenly the soil beneath our feet has the capacity to be the most immense sponge imaginable, mopping up the many thousands of litres of water which fall from the sky in a rainstorm. Good, healthy soils are therefore a huge tool in helping us to reduce flooding.
Unfortunately we have covered our soils with concrete, helping to create an impenetrable barrier to water which runs off our towns, causing scenes of flooding chaos such as those which were seen in Brighton and Rottingdean last month. For a concreted urban area of only 1000 ha, that’s over 170 million litres of water storage ‘foregone’ that we have created through urbanisation.
You might argue that so much of the rest of our country is covered in soil, that this shouldn’t really make a difference. However, in many places our soil management has become so poor, that large swathes are impoverished and compacted and act in a similar way to concrete – causing rain to run quickly off the surface, rapidly swelling our rivers and streams.
So as well as creating permeable urban surfaces such as porous paving, perhaps we should be trying to help reduce flooding by improving our stewardship of the countryside. Soil formation and retention is one of the key natural services that our landscape provides for us. Its value is often overlooked, and yet the benefits it provides us with are inestimable. I for one will be looking at my veggie patch in a slightly different light next week!