So how can I summarise in a ten minute opening speech (alongside contributions from a climate expert, a flooded resident and a firefighter) what are the most important things we need to do to become more resilient to flooding, and are we doing them? Well, as I've written in my earlier posts, to consider a problem holistically I like to start from first principles. So here is the flooding problem as we face it in the UK:
1) Rain falls out of the sky (and more rain is coming)
We live on an island next to the Atlantic Ocean, which is warming up as a result of climate change. The prevailing wind blows warm wet air over the UK, depositing its moisture as it goes (especially on the west side of the Pennines - sorry Cumbria!). My gut feeling in December was that something was seriously wrong with the weather and our infrastructure was likely to suffer the consequences. The Met Office confirmed this as the average temperature over the month of December was 8.0 degrees, a whopping 4.1 degrees higher than the long term average of 4 degrees and much larger than the previous record (6.9 degrees in 1934).
Warm winters usually mean wet and windy ones, as storms blow in off the sea and this winter has been unusual, but not unexpected given what we know about climate impacts. Therefore, while we cannot control the weather itself, we do have a choice about limiting our carbon emissions now to prevent making it worse.
2) When rain falls, the water needs to go somewhere.
The main factors which affect the proportion of rainfall which ends up in watercourses are:
- the soil type
- local topograghy (more water runs off steep slopes than gentle ones)
- saturation of the soil (the wetter it is, the less capacity to absorb more water - so even relatively little rainfall can cause flooding in late winter while the first heavy rain of winter is usually absorbed without a problem); and
- land use (trees and peat bogs absorb the most, livestock can churn the soil up or compact the surface, while paved surfaces run off almost all the water).
Engineers have a good solution to this, known as SUDS (Sustainable Urban Drainage Systems), which means that you include within your urban planning water storage features such as permeable paving, rainwater harvesting or ponds with reedbeds. There's a fascinating project in Llanelli in south Wales to retrofit SUDS to the whole town. But these require someone to maintain them - a theme which will recur time and time again.
3) Water flows downhill
The total volume of water falling on a catchment is equal to the intensity in mm/hour * duration of storm * area of catchment. However, flooding is not caused by the total amount of rain that falls, but by the peak height of the water in your local watercourse, which is affected by how long it takes for the water to travel from where it falls to a receptor (like your house) which could be affected.
Slowing the water down is an excellent way to reduce the peak height of water downstream, for example using weirs, meanders and flood storage using the floodplains like Clifton Ings upstream of York or the flood storage reservoir I built upstream of Wakefield. This also reduces the energy of the water, because fast-flowing water exerts a huge force on anything in its way which can damage buildings and bridges like the one at Tadcaster. A recent case study well worth reading is the Slowing the Flow project in Pickering, which deliberately built small dams and weirs to reduce the peak flow in the Pickering Beck.
Incidentally, dredging rarely increases the capacity of a watercourse significantly but can result in speeding up the flow, which means it is not usually the best solution to a flooding problem. It may of course be an excellent solution to the problem of allowing boats to travel up and down your watercourse without hitting the bottom.
4) Protect what's downstream
Given that we live in a wet country, we need to accept that land adjacent to our watercourses will flood on a regular basis. Flooding is only a problem if we insist on putting things we care about in the way of the water. Therefore, we have several options to protect our towns and cities:
- Avoid: Don't build on the flood plain at all (though these are tempting flat pieces of ground in the middle of our urban areas with a lovely waterside view!)
- Protect vulnerable assets (substations, telephone exchanges or hospitals) with flood defences, remembering that we must maintain them as a whole system including pumps and moving elements such as floodgates because the water will get in at any weak spots we leave.
- Floodproofing: Construct anything that needs to go on the floodplain in such a way that when it floods, it isn't a major problem. For example, waterside flats where the ground floor is used only for car parking, not for storage or living space, or the King's Arms in York where every surface is tiled, the electrical sockets are high on the wall not along the skirting board and all the furniture can be moved at short notice upstairs (even the toilet doors come off). When you come back, you wipe it down and carry on.
- Community resilience and contingency planning: Train people to respond to floods and have several back up plans - think "what if?" Flooding problems are often exacerbated by critical infrastructure failures which make it difficult to implement the original flood plan.
Liked this? See my book blog for reviews, author interviews and more at: www.EdBucks.co.uk
I'd like to get in touch - Kate Lock mentioned that you were interested in getting a Climate Outreach workshop on community responses to flooding together, but no longer felt able to because of other commitments. I am working on getting them to do a series of workshops in Yorkshire (I am the founder of Zero Carbon Yorkshire). Can we speak please? You can contact me at Schumacher North on 0113 350 8070 or at david@schumacher-north.co.uk. Apologies for the unorthodox method of contact - couldn't find another way to contact you!
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