Gardens and Flooding

Many houses and gardens have been affected by the devastating floods in recent weeks and months. The impact on our lives, business and our own health and wellbeing is phenomenal. I moved house a little over two years ago to escape the floods; previously we flooded three times – each time was the ‘worst ever’, a one-in-a-fifty year event, then a one-in-a-hundred year event. The evidence is that levels of rainfall are only going to get worse and that we have to react in as positive a way as possible, both to support ourselves and our communities, but to make us all more resilient in the approaching climate crisis.

Flooded gardens

Gardens are relatively resilient after floods. The worst plant damage we had was to shrubs – herbaceous perennials seems to live through it. Fair enough, the floods in the Calder Valley don’t last so very long before the ground starts to drain again. However, the mess, mud and sewerage cannot be underestimated. Don’t wade through flood waters, use protective clothing when cleaning up, and finish with disinfectant. Flood water can soften the pointing in your paving and walling. Have it checked. Spray-off the plants to remove as much of the mud as possible from the stems and foliage – they need to see the light and to breathe. Most importantly, don’t give up – start to love your outdoor space again and take pride in the how you will enjoy it in the future.

How to make our landscapes more future-proof is another issue. As gardeners, we should aim to make our own impact on the environment as small as possible. Often we wonder just what it is we can do to help in the face of government inertia and lack of guidance. We should definitely try to minimise our use of plastics; horticulture and gardening in general are not the best on recycling! I want to save plastics for another post, but look here instead at our approach to water in a changing climate.

We were told years ago that global warming meant hotter and drier conditions all through. It kind of sounded nice, once upon a time, when winters were cold, summers cool and wet. What played out was the extremes of heat, followed by years where the extreme rainfall causes flooding on a monumental scale. In my valley there is a community led organisation call ‘Slow The Flow’. It aims to create small dams of branches (much like a beaver may have made) in the upper catchment area of the river tributaries – each slowing the run-off from the hill, creating mini ponds and the water therefore not reaching the rivers in one almighty rush. ‘Slow The Flow’ are also closely linked to tree planting groups – trees create drainage channels with their roots and hugely help in areas of high rainfall, not least because trees take up huge volumes of water. Now, as gardeners we too can help. Garden Designers have long known about something called SuDS – Sustainable Urban Drainage Systems. The urban seems a little anachronistic right now, but all gardeners can help to ‘slow the flow’. Here’s how.

Collect run-off water in butts. When these overflow, send the water to overflow tanks, planted attractively and integral to the garden.

Collect all further run-off in a part of the garden called a rain garden; a hollowed area designed specifically to hold a volume of water on site during periods of excessively high rainfall. When empty they are a carefully designed hollow; when full they become small ponds.

Plant green living roofs on your buildings. This is easy on sheds and summer houses etc., but can have huge insulating benefits on house. However, a green roof also soaks up huge volumes of water, stopping that run off in the first place.

Avoid impermeable surfaces such as concrete and tarmac – the water will run straight off into the drains and add to flooding further down stream. Use gravels, and where you must build, try to use free-draining hard core (DTP type 3 is the technical name), and free draining cements for paved areas.

Plant as many different plants as you can, especially trees. Did you know that plants not only help with drainage and take up water, but they can also clean the nasties associated with flood water – they clean the soil? Contact me if you would like more information on MESIC plants – those plants which can tolerate extremes of climate, not least periodic flooding.

All of these elements combine into what is sometimes called the ‘storm water chain’, aiming to hold as much water on your site to stop flooding on a large scale, illustrated below.

Image courtesy of Susdrain.

Finally, don’t underestimate the healing benefits of gardening. Get back out there and enjoy it. Plants and gardens are proven to lower blood pressure, aid recovery and generally help with our mental health and wellbeing.