Physical barriers on rivers

Weirs on rivers can create physical barriers for wildlife, preventing access to the river above whilst also creating deeper water in places where fish spawn, which can result in fish drowning.  

We were delighted to support the West Wales Rivers Trust in a project involving the removal of a weir in the Loughor River. The work was inevitably going to kick up silt in the short term but it would provide far better environmental outcomes for wildlife in the long term.  

The West Wales Rivers Trust were therefore very keen to ensure that the silt was not transported downstream, which would have had detrimental effects on fish and invertebrates. 

Supporting local communities

We gifted the Trust a Bubble Curtain to help them achieve their environmental aims when carrying out river works and improvements. The donation was made from our Community Fund.  

“We are grateful to you, and the Frog Community Fund, for making the bubble curtain available to us. I think it will be a very useful tool for us to have access to and be able to deploy in future at project sites where controlling silt is an important element of the mitigation works.

“It will be excellent to be able to offer using the curtain within method statements and applications for permits / consents going forward, in particular with barrier removal projects.” 

Helen Jobson, Senior Executive Officer at the West Wales Rivers Trust

The curtain on the Loughor was trialled in Storm Agnes, which meant the river was full, making the conditions challenging, however, the curtains performed the task they were implemented for to limit the movement downstream of disturbed silt and sediment arising from the removal of the weir, and to reduce silt pollution and smothering of in-stream gravels/habitats as well as increasing the oxygen levels in the water. 

The West Wales Rivers Trust tried to achieve 2 lines of Bubble Tubing across the width of the river – but due to the high flows during the storm, it was difficult to get the tubing to spread out in a line and it ended up being a series of upstream facing curves. However, the bubbles still created a barrier to the silt, preventing much of it from being transported downstream. 

Even in the challenging conditions, it was obvious to the Trust that the spread of the micro-bubbles within the water column would have increased the oxygen levels within the water which would have been beneficial to any fish or other organisms present at the time. 

“Silt control in any river restoration project is very important to ensure success. 

“Bubbles create a flow pattern that hold silt and sediment back, the centre of the bubble curtain baffles and augments the water to prevent the movement of silts downstream. It also introduces oxygen into the water column improving the immediate environment for wildlife.

“We were delighted to be able to provide the Rivers Trust the Bubble Curtain as part of our community funding.”

Leela O’Dea, Technical Director at Frog Environmental

As you can see water flows were very high meaning that these weren’t ideal conditions for the bubble curtains, however, they were still effective. Thank you to the West Wales Rivers Trust for the footage.

Frog Environmental are water quality & silt control specialists working with contractors, regulators and consultants within construction, utilities, marine and coastal and public sector industries across the UK and Europe. We also support local projects through our Community Fund.

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