Bank Erosion Protection | River Taff, UK

1,040m² Riverbank Protection with CC13^® in South Wales

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Project Overview

In November 2016, Concrete Canvas^® GCCM (CC) was used as a remedial slope protection solution to line sections of embankments of the River Taff in South Wales. Sections of the riverbank are formed from grouted rip-rap embankments believed to have been installed in the early 1950s. A section was showing signs of degradation; the condition of the concrete riprap was heavily cracked, with severe spalling and established vegetation growth. Remediation was required to provide erosion protection to prevent scour that could undermine a walkway and adjacent industrial areas.

Rip-rap Embankment Prior to Remedial Work

1040m²

of CC13^® was installed along the embankment

220 linear

metres of riverbank protected

10m/s

flow rate in flood conditions

Solution

Re-pointing the rip-rap was a costly stop gap and wouldn’t address drainage issues. Replacing the rip-rap would involve costly excavation and fill import in a difficult access area.

Other solutions were considered, including sprayed concrete, in-situ poured concrete, gabion mattresses, vegetation mats, and hydro seeding. These posed issues such as need for specialist contractors, contamination, time-consuming formwork, heavy plant, and insufficient flow resistance.

The client specified CC13^® for the project based on the success of CC applications on previous schemes.

Geotextile Placement with CC13^® Deployment, Jointing at 150mm Centres and Hydration using River Water

Design & Installation

CC13^® Bulk Rolls specified
Riprap removed and slope graded and smooth prior to deployment
Geotextile placed on the slope first to prevent washout of fines through permeable joints
Vertical layup
Perimeter crest and side edges secured in anchor trenches
Clamping bar and anchor connection to concrete kerb at the toe
Screwed overlap joints (to relieve water pressures)
Once cured, slope was painted to blend into the environment

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Crest anchor trenching

Summary

Following the installation, the client discussed the possibility of painting the CC material to help it blend in with the surroundings faster than waiting for moss growth to occur over time.

Masonry paints a typically used to colour cured CC, but as this installation was along a river, a specialist paint was required to prevent harm to aquatic life. After a successful trial, the entire 220 metre length of the slope was painted green. The paint will continue to weather over time, and gradually blend into the surroundings.

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Completed CC13^® lined section of the River Taff

Painted CC slope

Concrete Canvas is an excellent innovative product for two important reasons: firstly it offers the required erosion protection to protect a critical asset and prevent future erosion. Secondly, it minimises the environmental effects that you would normally associate with other concrete products. It also has the added bonus that the product is maintenance free and quick to install, therefore offering huge cost benefits.

Phil Poole, Operations Delivery Technical Support Team Member Cyfoeth Naturiol Cymru / Natural Resources Wales