Weeding out the invaders

The cutting of the southern section of the Gloucester & Sharpness Canal between Sellars Swing Bridge and Sharpness High Level bridge is an annual event.

Floating pennywork covering most of canal with boat moored at side Floating pennywort, copyright GBNNS

It’s aimed at reducing the impact of the non-native invasive submerged aquatic Elodea nutallii, which grows from the bed of the canal up to a depth of 3m.

Importantly, as well as being one of our scenic waterways popular with boaters, the Gloucester & Sharpness Canal is still a commercial waterway too. This weed can grow extremely quickly causing a problem for craft through fouling propellers, blocking up mooring sites and generally being too competitive for the rest of the aquatic life in the canal.

How we make sure the waterways stay flowing

What many people don’t know is that it’s down to us at the Canal & River Trust, as the charity that looks after 2,000 miles of canals and rivers, to make sure this canal stays accessible and open for everyone. So, our own waterways maintenance team jump in their wellies and fire up a very special bit of kit. The video shows the launch of one of the two boats used as part of the weed clearing operation.

This boat carries a cutting blade, cutting with a scissor motion up to a depth of 2.5m and looks a little like a miniature paddle steamer that you might see on the Mississippi River!

The other boat rakes and removes the cut weed, which is deposited on the bank of the canal on the offside.

Our experience of this weed on the Gloucester and Sharpness Canal over the last 10 years has been that a late June or early July cut has been seen to have maximum impact in reducing the biomass. We try to remove as much of the weed as possible during the works but inevitably a small quantity will float down to Sharpness.

The cutting work duration is usually around five days and we notify the Environment Agency, Natural England, Bristol Water and our Fisheries Team in advance.

If you spot excessive weed blocking one of our canals, please let our waterways maintenance team know by calling: 0303 040 4040

Last date edited: 5 June 2018