I'm sure we would all love to see the staff CVs for the firm who won this opportunity. BEng? No. MEng? Absolutely not. Chartership? Impossible. Big yellow teeth, webbed back feet and scaly tail? Yes...

Centuries after being hunted to extinction for their meat, fur and scent glands, the Eurasian Beaver (Castor fiber) has been reintroduced into a four hectare area of the Spains Hall Estate at Finchingfield in Essex. The pair have been awarded the chance to reduce local flooding and improve biodiversity through the construction of their own lodgings.

Beavers generally work at night to bring trees they have felled, along with mud and stones into the river to construct a dam, largely for their own protection from predators. It is widely known that there are numerous benefits that occur as a result of the beaver's construction habits. These include an increase in biodiversity among fish (particularly migratory fish such as salmon and trout), the removal of excess nutrients, pesticides and herbicides from the water, denitrification, and possibly the most important to the general public, flood control.

By constructing so-called 'leaky dams', the beavers slow down flood waters across the river system. This happens because beaver dams have a certain level of 'freeboard' above the water level (That is the distance from the normal water level to the top of the dam). During times of heavy rainfall, the dam gradually fills up and slowly reduces excess rain water into the downstream river system. This is the main driving factor in reducing the height of the flood wave moving down the river. However, in addition to this the dam increases the height of the surrounding water table, thus reducing its gradient. This means that groundwater flows into the river system around the dam more slowly, further helping to reduce flooding. Furthermore, since the dam will increase the amount of water in contact with the ground, it is possible for more water to seep into the geology below the dam, instead of running downstream.

The example of the Spains Hall Estate, who are working alongside the Environment Agency, the Essex and Suffolk Rivers Trust, and Essex Wildlife Trust, is not the first time beavers have been reintroduced in the UK. However, this is a first for the county and will undoubtedly help us to understand how effective our furry friends are as flood engineers. Who knows, perhaps we will be starting an Argyll beaver-handling course in the coming years.

 

Charles Krolik-Root BSc (Hons) MSc MIEnvSc PIEMA AEA
Senior Consultant

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