Years ago, people in the Fens lay awake and worried about flooding. Nowadays, Dan Pollard stays up all night to stop it happening.

Eastern Daily Press: Denver Sluice, seen from the Ely Ouse side. Picture: Chris BishopDenver Sluice, seen from the Ely Ouse side. Picture: Chris Bishop (Image: Archant)

Mr Pollard, 38, is in charge of the Environment Agency's Denver complex of sluices, near Downham Market, which regulate water levels across much of the Fens.

Recent heavy rains have filed the Great Ouse and its tributaries the Cam, Lark, Little Ouse and Wissey to the brim. The water has to go somewhere, to stop it spilling over the floodbanks. That's where Mr Pollard comes in.

From his control room a stone's throw from the sluices, he can open the gates to allow water to flow out of the Ouse into the Relief Channel.

Eastern Daily Press: One of the sluices at Denver. Picture: Chris BishopOne of the sluices at Denver. Picture: Chris Bishop (Image: Archant)

With levels at their highest since the winter of 2012 - 13, the complex of man-made rivers needs to be constantly monitored, along with the amount of water surging through the gates. That means Mr Pollard has to stay up all night.

'In normal conditions I can get a gate setting I'm happy with before I go to bed,' he said. 'But when we've got flood waters, the gates need checking every two or three hours.'

Built after the catastrophic floods of 1947, the channel is an 11-mile long reservoir which allows excess water to be stored between tides, before being released into the tidal Ouse at King's Lynn.

Eastern Daily Press: The main sluice at Denver. Picture: Chris BishopThe main sluice at Denver. Picture: Chris Bishop (Image: Archant)

The quantities involved are mind-boggling. Water levels in the 80m-wide channel can rise a metre or more in the space of a single tide.

'I could store another 1.5m in it,' said Mr Pollard, surveying the levels as the water lapped onto the footpath. Asked how much that might be, he added: 'It's 11 miles long, 200ft wide - you could probably work it out, but not on the amount of sleep I've had.'

With levels high on the nearby Ouse Washes and the tidal Hundred Foot river, more than 55 cubic metres of water a second flow through the gates - enough to fill more than a couple of olympic-sized swimming pools.

Eastern Daily Press: The Relief Channel, seen from the sluices. Picture: Chris BishopThe Relief Channel, seen from the sluices. Picture: Chris Bishop (Image: Archant)

By taking that water safely out to sea, the Relief Channel defends thousands of homes and businesses.

One or two of the old farm labourers' cottages along the Ten Mile Bank still have tide marks left behind from the last major floods in 1947, before it was built, when the waters lapped at their first floor windows.

Eastern Daily Press: The equivalent of two olympic swimming pools a minute flows through when the gates are lifted. Picture: Chris BishopThe equivalent of two olympic swimming pools a minute flows through when the gates are lifted. Picture: Chris Bishop (Image: Archant)

Eastern Daily Press: The sluice near where the Cut-Off Channel meets the Relief Channel. Picture: Chris BishopThe sluice near where the Cut-Off Channel meets the Relief Channel. Picture: Chris Bishop (Image: Archant)

Eastern Daily Press: Denver Sluice, where water levels are at their highest since the winter of 2012 - 13. Picture: Chris BishopDenver Sluice, where water levels are at their highest since the winter of 2012 - 13. Picture: Chris Bishop (Image: Archant)

Eastern Daily Press: Denver Sluice, seen from the Ely Ouse. Picture: Chris BishopDenver Sluice, seen from the Ely Ouse. Picture: Chris Bishop (Image: Archant)