Project Focus: Canals provide capacity for 21st Century flood protection
A 19km stretch of canal near Glasgow is to be given a stormwater drainage role, in an innovative project which incorporates intelligent control in its water management plan
by Marc Barone, Managing Director, Water, AECOM
Two hundred years ago, canals were the arteries of commerce in the UK. They carried trade to and from busy ports and ferried the coal that powered the industrial revolution. But their dominance as transport infrastructure gradually dwindled away.
Trains and trucks supplanted barges as the primary movers of goods in the 20th Century. Once thriving commercial waterways declined into stagnation and neglect until, more recently, they were rejuvenated and found a second life as havens for wildlife and leisure. Boating, jogging, cycling or fishing along a quiet canal has become a wonderful way to escape the pressures of modern life.
Today, canals are poised to shoulder a third, complementary purpose, and one just as important as the two roles that have gone before.
As the UK strives to prevent the damaging effects of extreme weather and flooding, and mitigate the impact of climate change on water resources, canals are a vast untapped infrastructure for capturing, storing and transporting unwanted surface water, as well as supplying water into urban areas. Today’s quiet waterways have a dramatic new role to play as components of dynamic, effective floodwater management systems.
At first glance it may seem that a narrow, slow-moving canal offers little potential for alleviating floodwater risk. However, because they stretch over many miles, canals can add up to surprisingly large bodies of water. Moreover, they are manageable in a way that the natural watercourses of rivers tend not to be.
Take the 19km branch of the Forth & Clyde Canal closest to North Glasgow. This section alone, just under a third of the canal’s total length, has an overall surface area of about 42 hectares. That means you would need to feed in an extra 4.2 million litres of water to raise its surface level by just one centimetre along its length.
This particular stretch of the Scottish canal network is the focus of a pioneering new project called the North Glasgow Integrated Water Management System (NGIWMS).
Fresh ideas for stormwater management
With sewer networks reaching full capacity across North Glasgow, fresh ideas for surface water management were needed to improve the potential for future development in the area. Nobody would want to invest in new commercial or residential property if it stood at risk of inundation or increased risk to the city centre downstream, so effective flood prevention can be a key enabler when it comes to both development and redevelopment.
The NGIWMS concept was created in 2013 by AECOM in response to this challenge, supporting the development and regeneration of 260 hectares of land in the north of the city that would otherwise suffer from an acute lack of drainage capacity.
We established that a conventional solution would require a new 2km tunnel to carry water safely away from the site. The construction savings that arise from using the canal to transport water instead amount to around £10M, contributing to the economic feasibility of the regeneration project.
Work on the new water management system is expected to begin in 2017, with the first connections likely to be made in 2018. Completion will be coordinated with the regeneration of North Glasgow, with the first phase expected to be in the Sighthill area where 1960s tower blocks have been demolished over the past few years.
The approach is not, of course, to simply send runoff water straight into the canal. The Forth & Clyde Canal is a protected Scheduled Monument, an important part of Scotland’s heritage and a thriving, diverse habitat. It must be handled with the utmost care and consideration.
The NGIWMS concept employs a range of techniques to realise the canal’s water management potential while carefully safeguarding its ecosystem.
Foremost among them is intelligent control. A range of remote sensors will collect relevant data needed for real-time operational management of the canal. For example, storm forecast data will be linked to water level controls, so that the canal’s surface level can be pre-emptively lowered by up to 10cm in advance of extreme weather. This provides as much as 42,000 cubic metres of additional capacity.
It is also vital to monitor the quality of water within the canal itself, in surrounding watercourses and in any stormwater runoff diverted into it. Runoff will be actively treated to maintain the quality of the canal environment.
Currently, levels throughout the Forth & Clyde Canal system are kept topped up with a constant flow of water from two reservoirs. Once the NGIWMS is fully operational, a significant proportion of replenishment will be achieved through surface water runoff, reducing demand on the reservoirs and so helping to prevent summer shortages.
The NGIWMS concept is also not limited to the canal system, but comprises an integrated plan that views water in the area as a community resource. There are proposals to capture and treat runoff water for uses such as community car washing facilities, for example.
The overall project is being developed with the involvement of Scottish Canals, Glasgow City Council and Scottish Water as key stakeholders in the Metropolitan Glasgow Strategic Drainage Partnership (MGSDP).
If realised, the NGIWMS approach would allow Glasgow to claim a place at the forefront of best practice in urban water management, becoming an international destination for water engineers, infrastructure designers and city planners, whilst also creating opportunities for development and application of existing and new technologies to support the Scottish Government’s Hydro Nation aspirations.
Scotland’s Centre of Expertise for Waters (CREW) recently carried out an in-depth review of the NGIWMS project and concluded that it will provide a significant number of direct and indirect benefits, including socio-economic improvements such as health, wellbeing and resilience, and that the canal should continue to underpin future development and regeneration activities.
The development of the NGIWMS concept will create an adaptive and responsive system that will be resilient to climate change and will provide a drainage system for the area that is fit for the 21st Century and beyond.
Victorian engineers were almost certainly not looking two centuries ahead when they built the UK’s sprawling network of canals. They would no doubt have been surprised to see their work transformed from bustling transport infrastructure into welcome ribbons of tranquillity running through the hearts of modern cities.
But it seems likely that canal builders like Thomas Telford would have admired the ingenuity of today’s engineers, as they cleverly put old watercourses to an important new use.
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