Main Street, Prickwillow, Ely, Cambridgeshire, CB7 4UN
There is no doubt that sea levels are changing, the only question is by how much and how quickly.
Since the last Ice Age the country has been tipping on its axis so that the South East of England has been dipping slightly and North West Scotland has been rising slightly.
Many experts also predict an increase in sea level due to climate change. There seems little doubt that the world is, on average, getting warmer. Sea level rise due to climate change is predicted to occur because of expansion of a warmer ocean system and the melting of ice on land for instance in Antarctica and mountain glaciers.
Estimates of the expected change vary widely from as little as 400mm to as much as 7 metres over a century. It is very difficult to measure actual change in sea level as we have come to understand that the land masses are not static. In other words what reference point can be used to measure relative changes between land and sea.
Much of the information on this subject comes from satellite measurements but these can be subject to small errors that are very important when trying to measure small changes in height.
Planning in this region currently assumes a rise in level of 6mm a year over the next 50 years.
What do these possible changes mean for the fens?
The water control system relies on the ability to release water from the rivers at low tide. If the average sea level rises, the time available for water release is reduced and the safety margins built into the system are gradually eroded.
The land is protected from high tides by high banks around the coast and along the length of the tidal river from Kings Lynn to Earith. A rise in this high tide level would require higher banks to be erected.
Most of the time, the system works with plenty of capacity in hand. The danger points come with extreme weather events, particularly when storms in the North Sea producing exceptionally high tides coincide with heavy rainfall over the river catchment area.
Small increases in relative sea level (perhaps 500-700mm) can be managed within the current system as long as banks are well maintained. Slightly bigger increases may require "sacrifice" areas to be introduced so that in extreme conditions, areas could be allowed to flood in a controlled manner. These areas could become a valuable recreational and water supply resource as well as being important for flood protection.
Still bigger increases may require the main rivers to be pumped into the sea.
At the most extreme estimates of sea level rise, it may not be economic to continue to protect the area and the fens would perhaps once again revert to the swamp that it came from. This also applies to many other parts of the country and the wider world as probably the majority of the world population is currently living near to a coast or major river. In these circumstances, the fens would probably be considered a low priority.
Most housing in the fenland area is built comfortably higher than any likely future sea level.
However, many of the road and rail links and services (water, electricity, etc.) to the towns and villages cross lower lying ground and important decisions would need to be made about infrastructure if people were to continue to live here.
