Category #zebra mussel   Show all

• A Summer like no other for Bude's Canal

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  2022 has seen the driest summer in 50 years, with a drought covering Cornwall, along with much of the rest of England, officially declared on 12^th August. Prior to this, water levels in the Neet had been particularly low, resulting in no abstraction into the canal being possible from late June to early September. EA data showed rainfall totals for August ranged from 12% of the long-term average in north east England to a shocking 0% for us in the in southeast and south west of England.

  In response to the drought conditions, and possible catastrophic impact on aquatic life in the canal, Cornwall Council worked with the Environment Agency and South West Water to develop a response strategy, including provision for a fish rescue. Fortunately, rain was forthcoming in early September and a fish rescue was not needed. Nonetheless, in recognition that drought conditions are an increasingly likely consequence of climate change the partnership will evaluate its response to the 2022 event and continue to develop a plan to help avoid such low water levels in the canal in future.

  Due to the impact of the drought on the canal banks, particularly in the upper basin used by water-based activity providers, the canal remained closed to users due to safety concerns until a temporary launch area was opened on 23rd September.

  

• Developing the Bude Canal Dredging Scheme

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  The Bude Canal is an integral part of Bude - It is central to the identity of the town and is an amenity resource that contributes to the quality of life and well-being of a broad spectrum of the local population. The canal also plays a role in the strategic flood response for Bude, acting as a pressure value relieving the River Neet of flood water, and the Bude Canal and Marshes was the first site in Cornwall to designated as a Local Nature Reserve, providing habitat for a number of rare species, including successfully reintroduced water voles.

  The canal experiences high levels of silt accumulation as sediment particles are transported downstream from the catchment of the Rivers Neet and Strat. These catchments are largely covered with grass-based agriculture and there are good levels of year-round soil cover, nonetheless, soil is particularly vulnerable at times of intense rainfall and the catchment is flashy, meaning that following high rainfall sediment gets rapidly transported by increased flows with little opportunity to settle out before reaching a dead-end in the canal.

  

  A full dredging scheme was last undertaken in 2008 and since then, some excavation of material in the upper sections of the canal has taken place. Nonetheless, these high rates of siltation have meant that water depths in the canal have reduced and a dredging scheme is required to safeguard the canal for people and the environment.

  The dredging programme has been in development for some time, with the canal being a site a numerous complexities including that the lower reaches contain invasive non-native zebra mussels meaning that the dredged material must be treated in ways that mitigate against any risk to further spead in the environment. .

  Plans began in 2021 when a full bathymetric survey was undertaken to provide a high quality baseline of the volumes of silt involved. A dual frequency single beam bathymetry system was used for accuracy, and an almost silent electric outboard engine helped make sure that the survey didn't disturb wildlife. Find out more about the survey at: Bude Canal Survey — Exo Environmental (exo-env.co.uk)

  Since then, Cornwall Council has worked to develop a method that takes account of the constraints associated with the presence of zebra mussels, but also involves alternatively, lower impact, methods where possible. The scheme is being developed in close association with the EA and SWW, including with advice from a zebra mussel specialist whose research into their ecology in the Bude Canal is funded by SWW. To read more about this partnership see: Help protect Bude Canal for future generations (southwestwater.co.uk)