New silt modeling methods by Dr Graham Daborn, Acadia University Centre for Estuarine research, Nova Scotia, helps us understand just how fast mud is deposited. A Severn barrage could lead to the beaches of Wales and the South West being plastered with a living slime of mud.

Traditional models like those now being used on the Severn, treat silt in the same way as sand, a non-sticky grain. Silt however is a living thing. It is full of tiny life. These mini molluscs, bacteria and worms secrete mucus that hold the sediments together. Dr Daborn’s studies have shown that this produces deposits 80 times stronger than traditional models expect and who not wash away. He states that, ’such accumulations would quickly fill up an estuary’.

The outdated models are being used right now to give misleading information to the company doing the feasibility study. Using incorrect modeling has lead to disasters in the past. Dr Daborn gives three examples in Canada where this has lead to barrages being constructed resulting in massive sediment deposits choking the river, leading to flooding and blocking harbours and destroying fisheries. Mud was deposited at a rate of 15cms per month. This mud now extends 11km down stream of the barrage and is still growing. On the Severn this would plaster the beaches of the SW and South Wales with a living slime of mud. The beaches would be gone.

Silt arrives in the Severn from both direction leading to choking mud downstream of a barrage and silting of the ‘head pond’ above it. Resulting in loss to the economies of coastal resorts and harbours and increased flooding above and below the barrage and loss of generating capacity.

It is time we admit the fact that the Severn Estuary is not suitable for a barrage. Research by Dr. Daborn and other experts from around the world shows it simply just would not work.

Full extract of Dr. Daborn’s barrage study can be seen here:

http://saveoursevern.org/dr-graham-daborns-report-on-silting/