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Managing & Maintaining our water channels

Dredging and de-silt

Silt removal on the Ouse

left high and dry

“Currently, when the tides are low, boats risk getting grounded on the island and we can only lock craft through on a very high tide. It is important that we carry out this work to ensure the river remains navigable.” Nathan Arnold, Waterways Team Leader

Every two years a silt island forms, just downstream of the Denver lock, near Downham Market. The island forms due to the tidal nature of the River Great Ouse at Denver Lock.

The silt causes a potential flooding threat as well as causing problems for the boating community, with boats getting stranded until high tides come to their assistance.

The Environment Agency turned to

contractor ADC (East Anglia) Ltd who have a specialist piece of equipment to carry out the task. A Conver silt-pusher was used push the silt across to the bank where it could be removed and left to dry. Once dried, it is then used to maintain flood banks in the area.

The Conver Silt-Pusher, used by ADC is unique, being the only one in the UK. They are widely used in Europe and in it’s native country, Holland, 75% of waterways are cleared using silt-pushers. It is capable of working at widths of between 1 and 4.5 metres. collecting up to 10m3

1500 tonnes of silt were cleared using the silt pusher, taking just over a week, with the work only taking place at low tide to minimise disruption to boaters.

of material in

a single push. With a draught of just 450mm, it can navigate some of the shallowest and most inaccessible inland waterways and operates to a maximum depth of 1.2 metres

It cost the Environment Agency £38,000, to complete the removal and they are looking into solutions that prevent future build up by catching the silt as it comes in on the tide.


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