- 8th December 2016
- Posted by: Joanne Woodhouse
- Category: Blog
Around 50 people from government agencies, local authorities, consultants and NGOs from across the UK attended the ‘River Weirs: design, maintenance, modification and removal’ guide launch event in London on Wednesday 6 December.
Fola Ogunyoye, a member of the Steering Group who has been involved with the project for its two-year duration, chaired the day with guest speakers from Dr Amanda Kitchen and Andrew Kirby.
The River Weirs – Good Practice Guide was first published in 2003. Since then there has been over 30 fatalities (an average of two a year) at weirs in the UK. Environmental legislation and good practice has also changed – a key milestone being the implementation of the EU Water Framework Directive.
The new guide therefore strives to update good practice approaches and has been funded by The Environment Agency, SEPA, Scottish Government, Rivers Agency, Waterways Ireland, Scottish Canals, Canal and River Trust, JBA Consulting and Mott MacDonald.
How did they do it?
A literature review and assessment using a ‘maturity matrix’, rating the information between ‘emerging’, ‘disparate’ and ‘mature’ evidence/guidance, helped inform the gaps in the existing guidance and the need for a new guide.
A wide consultation exercise was undertaken with regulatory and management authorities covering a wide range of weir types and uses. Key issues identified were on: weir removal, fishery considerations, debris/sediment management and balancing heritage, functional needs and the environment.
It’s all about the contents
The guide has 295 colourful action packed pages split into 3 parts which can be read together or independently:
- An overview – aimed at everyone with an interest in weirs
- The essentials of weir management – aimed at those responsible for policy and decision making
- Detailed technical guidance – aimed at those responsible for designing and constructed weirs or weir removals and managing weir assets.
Each chapter has a common structure: dealing with the issues, outlining methods of addressing them, and providing references and examples. In the Appendices, there is a ‘top trumps’ style summary of the 16 typical types of fixed or moveable weir and 18 case studies.
‘Is there a need to intervene?’ is a key theme of the guide which reflects that the function and environment of a weir can change with time. It also explores the range of options available – avoiding the need for a weir, removing or refurbishing a weir, or replacing or allowing existing weir to fail.
The guide covers the design, implementation and monitoring of weirs and is dealt with under several interlinked headings:
- Asset management
- Law & policy – looking at duties of owners
- Operational safety
- Natural and historic environment, landscape impact
- Geomorphology of the river channel and the impact of the weir
- Hydrology and hydraulics – including modelling, scour protection and air entrainment
- Foundations & geotechnics – seeking to plug the gap of lack of codes of practice or Eurocodes that can be readily applied to weirs
Six case studies were presented at the launch with four included in the new Guide.
Case study presentations
Our very own Jeremy Benn presented two case studies to delegates. The first was on the removal of weirs on the River Irwell in Lancashire as part of work to improve fish passage and restore natural river processes. An example was given of the Prestolee Weir and how the removal of part of the weir was largely based on geomorphological audit and the findings from previous weir removals on the same river.
The second presentation was on the Derbyshire Healthy Weirs Project, a community led initiative to help preserve and enhance the historic weirs within the Derwent Valley Mills World Heritage Site. The project has involved the recruitment and training of 50 unpaid volunteer ‘Weir Watchers’ to monitor and inspect 10 of the weirs. The CIRIA Weirs Guide was used to provide training material for this.
Following the presentations there was a Q&A session. One attendee said they were very encouraged from what they had heard asking what the intention was from regulators to adopt the guide. Andy Tan (Environment Agency) responded that he believed the intention is to cascade the guide down within the EA organisation so that designers and promotors of work to weirs and consenting authorities are in step.
Want to know more?
CIRIA are keen to hear suggestions starting with seeking feedback from those who read and use the guide. A free copy of the new Weirs Guide and copies of the presentations from the launch workshop are available for download from the CIRIA website.