SRA Annual Report 2025-26: dredging and silt monitoring
In January 2026, 4 kilometres (2.5 miles) of the River Parrett between Burrowbridge and Northmoor Pumping Station was dredged with a Water Injection Dredging (WID) vessel working in combination with an excavator mounted on a floating platform in the river.
Since 2014, SRA partners have concentrated on this section of the Parrett because this is where most sediments are deposited, as incoming tides jostle with outgoing flows. This is where regular dredging is most needed. Works done here have the biggest impact on how much water can be conveyed by the Parrett, as part of the same key system as the River Sowy and King’s Sedgemoor Drain.
Combined dredging was organised for the SRA by the Parrett Internal Drainage Board (IDB), working with SRA partners and contractors Van Oord and WM Longreach. It followed on from similar works with the same participants in January 2024 and January 2025. Around 30,000 cubic metres of sediments were moved in three weeks, quite a large amount because last year’s dry summer meant a prolonged period of low flows. So there was less flushing out of silt through natural processes, and more silt building up and sticking around.
Two methods of dredging were used in combination. The first involved the WID vessel Borr working solo, jetting out powerful sprays of water just above the river bed so that various sediments (sands, silts and clays) were separated and mobilised. They were then washed away in what Van Oord call a ‘density current’ in the lower third of the river’s water column. This ‘density current’ travelled downriver on the outgoing flow and dispersed through natural processes, chiefly disruptive wave action. That force broke the bonds in the ‘density current’ so that sediments once again became part of the gigantic natural load that has been carried by the Parrett in and out of Bridgwater Bay for thousands of years. All forms of dredging the Parrett have only ever had temporary results. The key point with this method of maintenance is that sediments get unstuck from the channel so the channel’s capacity is increased for the best part of a year, until sediments solidify again, as naturally they always have and always will, to a point where more dredging is called for.
The second method used in January was an extension of the first. An excavator on a floating platform scooped accumulated sediments and plants from the so-called ‘shoulder’ of the river, then it dropped them down into the central part of the channel. Along that channel, the WID vessel used the same powerful jets of water just described to agitate and disperse the materials placed in its path, so they got washed out on the outgoing flow. The importance of ‘shoulder’ works is that once sediments get stuck in bankside vegetation they further clot and strengthen, and get harder to erode. This clagging reduces the Parrett’s cross-sectional area and its effectiveness as a flood channel evacuating water.
Twice a year since 2015 the SRA has funded silt-monitoring, which involves surveying the shape and size of the Parrett’s channel. Resulting information has been used to help target dredging. The SRA’s aim has been to maintain benefits achieved in the major £6million dredge of 2014, through methods much cheaper, much quicker and much better for local residents (for example, no road closures). In combination with other elements of the SRA’s overall programme of works, SRA-funded dredging has helped to protect around 1,300 homes and businesses, around 7,500 hectares of land, 5.3 miles of A-roads, 30 miles of minor roads and 5 miles of main line rail network. It has particularly benefitted the area around Moorland which was so badly hit in 2014 – but much less affected in 2026, following on from all the numerous works done since 2014.
Resident’s feedback
“They say don’t work harder, work smarter, and this is exactly what has been achieved through using water injection dredging in the River Parrett between Burrowbridge and Moorland. This innovative approach makes maintaining the Parrett’s optimal profile feasible in both logistic and financial terms. I have no doubt that without this work, houses and farms would have flooded since 2014, particularly in the villages of Moorland and Fordgate.”
Rhona Light, local resident