Helston Flood Alleviation Scheme

A new flood defence covering 600 metres of the River Cober at Helston.
Climate Change Adaptation Resource Use Case Studies

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Project Overview

The £3.4 million Helston Flood Alleviation Scheme involved the construction of a new flood defence covering 600 metres of the River Cober at Helston, which has a long history of flooding. The scheme was split into two phases, to jointly manage the flood risk of waters backing up from Loe Pool downstream, and high river flows from the River Cober upstream.

  • Phase one was completed in 2019 and provided additional capacity for river water to be discharged downstream and out to sea through the installation of a new 185m long and 1.8m diameter flood relief pipe.
  • Phase two, which was aimed at reducing flood risk on the east side of the River Cober, was completed in 2020 and involved construction of a reinforced earth flood embankment, road ramp, floodwalls, two stop log access ways and a flood gate on an access bridge. The latter will be closed when a flood alert is issued. This second phase involved working within Covid-19 restrictions to be ready before the first of the winter storms, and combined with the work from phase one, is helping to protect more than 120 local homes from flooding.

Location

West Cornwall

UK availability

Yes

Date added

Feb, 2022

Project partners

Client: Environment Agency; Designer: Arcadis (as JacksonHyder); Contractor: Kier; NEC Project Manager: Arcadis; Principal Designer: Binnies; Supervisor: Jacobs

Project status

In use. Completed December 2020

Links

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Case Studies submitted by

Environment Agency
Arcadis

Key Sustainability Objectives/ Outcomes

The project’s focus on sustainable solutions was key to its success, with design and construction considerations including:

  • The use of lightweight and locally sourced concrete shuttering blocks and 5,000 tonnes of locally sourced soil waste materials being used to lower the project’s carbon footprint significantly through significantly reduced haulage requirements. It also resulted in a saving of 5,000 tonnes of primary materials, whilst supporting the local area’s economy, as 99% of the project’s materials (by weight) were sourced locally.
  • Ensuring any existing trees remained in place wherever possible to protect the natural environment and local surroundings.

Notable Approaches And Solutions

This was a challenging project, with work starting on site only a month before the first national lockdown in February 2020. However, with additional safety protocols in place, work continued throughout 2020 – except for a four-week period in April when materials could not be sourced.

In addition, along with having to manage environmental restrictions for river working timescales, most of the floodwalls’ construction work had to take place within small private garden areas during lockdown, which meant that, to ensure residents’ safety and to maintain positive relations, great care had to be taken to minimise any disturbance to the lives of local residents.

Lessons Learnt

Amongst the challenges faced were the key issues of public acceptability and environmental sensitivity. The work was to be constructed in people’s back gardens and a lot of effort was placed in consultation with the local residents both before and during the works. Senior management visits from the Environment Agency and Kier, at Area and Director level, led to the following comments:

  • “Your approach and clear commitment to applying robust Covid-19 protections keeping both the team and local community safe were exceptional.”
  • “Engagement with the local community, and the clear warmth the local community and impacted residents have for Kier and the workforce was quite outstanding.”
  • “By building great relationships, being polite and courteous, amending the programme to reducing disruption and nuisance, and by dealing with individual concerns so quickly, you have not had one single complaint! This is fantastic and you should all be very proud!”

The upstream end of the site was along a heavily wooded riverbank. The downstream end was within a Conservation Area and abutted a Grade II listed Building. The design was handled sensitively and it was agreed that the flood embankment footprint would be minimised and built on top of the tree roots to minimise tree loss. The walls were designed with a specially formed half-round coping to match walls in the local area and a half-round security fan was placed at the downstream end to prevent children walking along the top of the wall but designed in such a way as to replicate Historic railing in the area.

Related members

Environment Agency

Arcadis

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