COMBE VALLEY FLOODING – WILL IT END IN TEARS?
a blog essay by David Dennis
Will global warming and rising sea levels cause a flooding disaster in Combe Valley? This sounds like an apocalyptic caption for a far-fetched film. What could possibly go wrong? Let us peer into the future and see what the legacy of mismanaging nature is bringing our way.
In April 2002 the UKCIP02 Scientific Report called Climate Change Scenarios for the United Kingdom was published. It explained that the planet was getting warmer, that as a consequence of this heating (molecular vibration and spacing) the sea was expanding and rising. With an overheated energetic atmosphere causing storm surges with greater power and frequency, coastal flooding was more likely around the world.
Now our government has produced this latest report which sets out the flooding containment strategy:
The melting of sea ice north and south makes very little difference but the melting of Greenland and Antarctic ice sheets is the danger. Add to this the increasing turbulence of the atmosphere and the storm surges that weather systems produce, and it can be seen that coastal, estuary and land drainage problems will increase. Sea level rise estimates vary wildly from a few centimetres to one metre within a lifetime. In addition to storm surges there are annual tidal fluctuations. If a storm surge coincided with spring tides for example, then rivers would back up and land would be flooded a long way inland, especially if rainfall had been high and river gradients are shallow – remember Somerset in 2014, for example.
Our part of England has been slowly sinking over thousands of years and many coastal harbours and marshes have been formed. Pagham Harbour and Selsey Bill, the Cuckmere, Eastbourne and Pevensey Marshes and the Combe Haven valley are all shown as being flood-prone on the national flood maps set out by DEFRA on the internet for all to see.
Rainfall intensity in our Bexhill-Hastings-Battle-Crowhurst area is greatest in October to January with total rainfall for those 4 months in the Combe Valley being 15 inches (384mm). The ground becomes saturated and water tables are high. Since there is no regional strategy to help farmers to control run-off from fields, the water in the Combe Valley accumulates, much to the delight of wildlife observers, lovers of marshes, reed-beds and waterfowl.
But this huge volume of Combe Haven water with its Watermill and Powdermill tributaries has to get to the sea. To do this the Haven has to flow past Combe Haven Caravan Park part of which is built on its flood-plain, it then flows between Bexhill Road and Bulverhythe Road to the sluice and the sea pipe just before Bo-Peep.
The sluice can only be opened to let the water out to the sea when the tide is low enough. Here lies the problem because the number of hours available for the sluice to be opened will depend on the height of the tide – and the tides are rising by a known amount.
In the last 100 years the sea in Sussex has risen by 10cms. Due to planetary warming, the Sussex sea level is expected to rise by 55 cms by 2080 or 85mm per year.
As the Sussex climate changes with drier summers and wetter winters, the plants and animals will be affected. Some winters may be so wet as to kill off some types of life and some summers may be so dry as to kill the roots of plants and trees in the natural environment.
In Combe Valley, the growing intensity of the rainfall within a short duration and the rising sea levels closing the sluices will leave Combe Haven Caravan Park managers to build higher and higher barriers to save their flood plain caravans. As they do so, understandably protecting their commercial interests, the flooding of the Bexhill playing fields and homes backing onto it will get worse since the water in their kitchens would have been lower if the flood fencing had not been so high.
So what to do? Do we ask the Caravan Park owners to remove their caravans and free up the flood plain expansion point, or tell the people of Bexhill Road to move? Is there a third or even a fourth alternative?
Pumping the Combe Haven excess flooding at a very fast rate during low tide times will cost money but it is obvious that a powerful pump could keep water levels lower than they are now despite rising sea levels. Powerful pumps cost money. There is little government money available for such engineering, but Hastings Borough Council is looking at loaning money (£6 million?) to pay for such pumps so that they can build a housing estate on Bexhill Recreation Ground.
A fourth alternative would be to ask the farmers to plant more trees and cut more ditches to slow the run-off of rainwater. But harsh strategies such as turning the Combe Valley into a permanent lake or reservoir would just mean the total loss of all farmland and the Haven is not suitable for building a dam in any case as the valley has such a broad front. Using the part-natural choke point between the hill made by the now closed tip and the hill slope of the caravan site would mean the total removal of the caravan site – and in any case the water would flow out through Pebsham and Sidley and the stream at Crowhurst would back up, flooding the cricket ground. At the end of the last Ice Age, Combe Valley was tidal to Filsham Reed Beds and so it would become again. A salt marsh would develop similar to that planned for the Cuckmere which has had its flood defences removed.
So pumping seems to be the short-term answer with the money for this found from private sources perhaps.
How long have we got before disaster strikes? The forecast for Pagham Harbour and East Head nature reserve at Chichester is that the next big storm surge will destroy these two landmarks permanently. Along the Bexhill coast to Hastings, there are clear signs of concern as the beach is supported by rocks to save the railway and the Fairlight cliffs topple into the sea on live TV. Even the wavecut platform of sandstone rocks and the petrified forest at Bexhill are collapsing, with huge pieces breaking off – never seen before in my lifetime.
I am personally convinced about global warming. I have walked on the Greenland icecap and seen its erosion and lived on and mapped the retreating glaciers of the Okstind range in north Norway, so I can safely say that Nature is coming to get us. When you sleep on a glacier, the night is silent but by noon to 3pm the whole surface is melting – thundering and roaring down through cavities to lubricate the underneath and make the glacial ice flow faster to the sea. If the Greenland icecap melted totally the sea would rise by a small amount, but – as the UKCIP02 Scientific Report states, if the whole West Antarctic ice-sheet melted the sea would rise by 5 metres and Bexhill would be taken over by fishes.
As a conservative estimate, the government is looking at a range of a few centimetres to 2.5 metres for Britain. So a local debate is required. There will be more winter rain, higher tides and more storm surges for sure. What shall we do about it? Shall we continue to build homes along the coast? Your comments are welcome.
I will publish some of them in my blog – maybe in shortened form but without personal names unless you say not to in your replies to this blog essay.
Kind regards to all