Most people would have seen the flooding in Cumbria (and Southern Scotland) this December (2015) where the rivers became swollen and breached the flood defences in Appleby, Keswick, Pooley Bridge, Dumfries, Carlisle and elsewhere… there was a lot of talk on TV saying how there was “unprecedented rainfall” in Cumbria since records began. This rainfall fell on high ground (Lake District fells and the Pennines) and this saturated the ground and this fed into the rivers and they became torrents. These rivers all fed into the River Eden and this fed into the sea.
The last time this flooding happened was in 2007 (in fact there were smaller occurrences since 2007 but these did not make major news), and at the same time as the swollen rivers there were also very high tides on the Solway Estuary.
The various government agencies when looking at why the flooding happened in Carlisle only seemed to asses river levels. Their results focused on building flood defences, after estimating the future river levels.
What they did not notice or what is not so evident from news broadcasts is that the river levels reached their highest point around the area of Carlisle City because the flood water from rivers met the flood waters from the sea.
Carlisle is tidal, not many people know that. I have been carried all the way up to the outskirts of Carlisle by high tides. Starting at Drumbrugh in my sea kayak I was taken past Rockcliff and I was easily able to kayak up river Eden, have a sleep near to Cargo and come back on the same tide.
A week before Carlisle got flooded I was told and shown a video of the high tides at Port Carlisle. High tide was supposed to be at 4pm, and generally the tide starts coming in 1-2 hours before that. It races in and goes out more leisurely. But that week they were coming in about 12 noon, so that is 2-3 hours more water than usual. Therefore it is lingering longer and going out slower. That build up of water in the estuary and that water flowing over the salt marshes and up the river Eden would have a drastic effect. It would meet the River Eden in flood and the two waters would collide. It is possible they met near to Carlisle and they began to build up and over flow their banks.
There would have been no outlet for the meeting of the waters. The tide goes out and there is roughly 6-8 hours of dry sands (and salt marshes) for the rivers to drain into. Because of the tide lasting longer in the river Eden, and because of the tide covering the salt marshes and staying longer there, this would give time for the flooded rivers stay longer or to be held up moving on… they would build up on top of each other, there would be nowhere for the river to go except to widen its course.
They will talk of new defences again I am sure after the floods have gone and they will assess the damage. But I wonder if they will look at the sea?
I am not just going to criticize; one solution could be to divert the flooded rivers before the flood plain, somewhere before the motorway bridge, east of Carlisle. A canal or many irrigation ditches could be built and managed, so when a tidal surge and flooded rivers are likely to collide the canal’s gates could be open to let the flood waters be channelled in a direction away from the River Eden and Carlisle.
The area historically known as “The Debatable Land” is mainly low land, farm land and not used extensively. These flood canals could be fed into them causing little risk to houses or to live stock, they could be dug all the way to Rockcliff marshes and there (when the tide goes out) let onto the marshes to drain away with the tide’s ebb. The diverted route is perhaps 7-10 miles and this is already an extensive amount of water to fill the canals.
The cost of this could be considerable, but compared to the human loss and building flood walls which might add to the problem elsewhere it could be a solution. The canals could be used as a recreational waterway when the floods are not with us. Boating and kayaking, small craft sailing, swimming and walking along the dyke could be one way of creating income to pay for it.