Flood Risk

Most economic activities in this generation pose a problem for our descendants, mainly global warming and resource depletion. A Barrage is unique in leaving them a productive and protective legacy.

There is a flood risk with every river. At present the risk is reasonably well managed, although the Environment Agency is not well funded for improving flood defences, and local authorities persist in building on flood plains.

However, global warming will increase the risk both as a result of increased frequency and intensity of storms, and also as a result of sea level rise.

This threatens the security of all the low-lying and, including human settlements along Severnside in the long term, perhaps in one, two or three generations. At first, the Barrage will protect against storm surges. It can also help protect against river floodings that seem not to be an annual event, since closure of the sea sluices on the barrage could keep river levels lower at times of high spring tides. High tides in the lower Severn stop rainwater pulses from draining away.

Eventually, if we do not manage to stop and reverse climate change, the barrage would act as a permanent sea wall keeping the Atlantic out of the Severnside region.

The ability of a Barrage to prevent the loss of these lands and settlements may be of even more value than the energy that the Barrage would generate. It should be noted that when the Barrage becomes a dyke to keep the sea out of Severnside, it will no longer generate electricity.

When an out flow into the sea is no longer possible, because the sea is above the level in the Severn Lake. the threat of flooding will change to a threat from the continual input of the River Severn. At this point, huge water management solutions will have to be put in place to transfer all river water - apart from a small amount needed to replace evaporation losses from the surface of the Severn Lake formed behind the Barrage - to areas of Britain which are short of water - namely the South East of Britain. It is possible that water exports to France will also be possible.

Note: The Barrage would be a far more efficient way of preventing flooding than trying to erect flood defences around the entire coastline, which would involve hundreds of miles of sea wall, which would themselves be more disruptive to wildlife than the Barrage.

Objection: Surely we should be preventing sea level rise, not responding to it?Prevention or cure?

There is a known negative flooding effect of the Barrage. Drainage in Newport and other places relies on releasing water at low tides. Since this low tide will disappear, these drains will have to be re-engineered.

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