Glasgow flood defences effort makes difference

A complex partnership is reaping the rewards of integrated surface water management in Glasgow. MWH programme manager, Jeremy Osborne explains

The world's largest Hydro-Brake is installed at Blackhouse

The world's largest Hydro-Brake is installed at Blackhouse

Greater Glasgow, in the guise of the Metropolitan Glasgow Strategic Drainage Partnership (MGSDP), has adopted an integrated surface water management approach to enable it to understand and predict urban drainage flood risk across the Metropolitan Glasgow area. It's vision is that "The MGSDP will work collaboratively and innovatively to provide effective and sustainable drainage and sewerage systems for Metropolitan Glasgow that will reduce future flooding risk, support economic development, while improving water quality and enhancing the environment, within a changing climate."

One of its most significant projects to date has been the Glasgow Surface Water Management Study (GSWMS), which is already providing direction and guidance to support future design and planning to reduce flooding and overflow spills. Formed by organisations involved with the operation of the sewerage and drainage network within the area, this unique partnership within the UK is a good model for how all stakeholders can work together to create the best solutions for their region.

The really interesting thing about this multi-partner approach to managing flooding is that it includes not just commercial firms like the UK's leading water and environmental specialists, MWH and Halcrow but for probably the first time, it brings together many public partners. For example Glasgow City Council (GCC), which is responsible for roads drainage, watercourses, and flood risk; Scottish Water, which is responsible for the sewerage network; Scottish Environment Protection Agency (SEPA), which is responsible for water quality and flood advice; other key partners - Clyde Gateway Urban Regeneration Company (CGURC), British Waterways (Scotland), responsible for the canal network across Scotland and South Lanarkshire Council, Scottish Enterprise, Scottish Government - and the Clyde Valley Strategic Development Planning Authority all have an involvement at the highest levels.

Technical support
The combined team of MWH and Halcrow, were chosen by the MGSDP to form a Programme Management Office and to provide technical and programme management support to the partners in developing an implementation plan responding to the complex challenges facing Metropolitan Glasgow.

The overarching aim for all of the MGSDP Partnership is to provide a holistic approach to managing surface water which will reduce flood risk and unlock development potential as well as improving water quality and allowing residential areas to co-exist with the natural landscape.

Integrated approach
The GSWMS, is proving key to driving an integrated surface water management approach by providing a strategic understanding of the urban drainage and flood risks across the Metropolitan Glasgow area. The study used Innovyze's InfoWorks integrated catchment modelling (ICM) software to develop integrated below and above ground drainage models to predict flooding across Glasgow. By analysing flood consequence, available data and potential opportunities in each drainage community, it allowed the identification of high priority drainage communities (HPDCs).

The modelling produced results for each return period showing where flooding would occur from - its source, the routes it travelled overland (known as pathways) and the locations impacted (known as receptors). Following the completion of risk assessments to determine the consequence of flooding, average annualised damage (AAD) was used to estimate the economic costs for each property type and then potential retrofit strategies to support the development of the modelling guidance were prepared. The CIRIA project, Retrofitting Surface Water Management Measures, formed the basis for the development of high level improvements in each HPDC.

MWH director and programme champion Craig McMaster says: "Outputs focused not only on managing surface water to reduce flood risk, but also followed the ethos of surface water management in optimising available drainage system capacity, utilising natural reduction and improving water quality by mitigating the impacts of urban creep and climate change."

The GSWMS is intended to provide direction and guidance to support future design studies and master plans using Surface Water Management Measures (SWMM) to reduce flooding and overflow spills. It will be integral to the delivery of sustainable urban design development and regeneration processes across Glasgow.

Social benefits
By relieving pressure on existing drainage systems through reducing the need to handle as much surface water, MGSDP is providing economic and social benefits, including support for modern urban development, new water based features for local communities to enjoy and improved natural habitats for wildlife. Sustainable urban drainage schemes (SuDS) are a key component in achieving this in MGSDP projects. For example, inspirational plans for South Dalmarnock integrate SuDS into the design of a new community in Glasgow's East End have received industry acclaim for its innovative approach to place making. The proposals seek to provide a flexible development framework for the area over a 20-year horizon, which is founded on strategic surface water management and infrastructure.

As part of the Clyde Gateway urban regeneration programme, a new mixed neighbourhood will be created which will provide modern office and industrial premises, new housing, community facilities and open space and recreational areas. Initial remediation, SuDS and flood retention works commenced in summer 2011. The South Dalmarnock scheme is part of a larger regional approach to the management of surface water within the Clyde Gateway area. MWH's Craig McMaster explains that MWH supported the Scottish Government in the development of what is now the Flood Risk Management Act, and now, through the MGSDP have been commissioned by the Scottish Government to provide guidance to help with the implementation of the Act. To date the MGSDP has provided:

  • Guidance on collaborative working to help chart the way multiple public and private agencies can successfully work together to deliver flood risk mitigation measures
  • Risk-based design - a new approach to assessing the risk from flooding and targeting minimal funds where they can generate most benefit

The MGSDP has also developed guidance documents that will help people working in surface water management in Scotland. These include:

  • Carbon accounting - to help policy makers and practitioners to take full account of carbon impacts in options appraisals and designs
  • Cost estimating - how to ensure that the cost of a scheme can be agreed by multiple funding agencies
  • Climate change - what are the likely effects of climate change and how they can be mitigated in the design of flood risk mitigation measures

The future of the MGSDP is being chartered by the partners to respond to changes resulting from the Flood Risk Management Act and the Local Flood Risk Management Districts that SEPA has established across Scotland. MGSDP can be seen as wholly encompassing the Glasgow area and one of the 13 areas that form the Clyde and Loch Lomond Flood Risk Management District. This district has nominated Glasgow City as the lead agency and so it is expected that MGSDP will operate in partnership with more agencies and from a position of leadership, not just of the Clyde and Loch Lomond Group, but of Scotland.
www.mgsdp.org

First test passed
Just four weeks after the White Cart Flood Prevention Scheme had its official inauguration, the new flood defences successfully held back rising water during a storm at the end of November 2011. Officials at Glasgow City Council said that all the defences were monitored throughout the flood threat and they worked extremely well.

It is estimated that nearly £11m of flood damage would have been inflicted on homes and businesses in the south side of the city without the defences. The world's largest ever Hydro-Brake Flow Controls are central to the £53M scheme, which is supported by the MGSDP and is designed to protect 1,750 properties from the risk of flooding. The Hydro-Brake Flow Controls constructed in three dams are designed to hold back water in three flood storage areas, which together have the capability to hold back millions of gallons of floodwater generated by extreme rainfall.

Manufacturer Hydro International says it had to pioneer new manufacturing and installation techniques to construct the 8m-long, 6m-high, cone-shaped devices, which were positioned in dams at Blackhouse and Kittoch. A further three Hydro-Brake Flow Controls were installed in the dam at Kirkland Bridge. With a combined stainless steel weight of more than 60 tonnes, all five are the biggest ever produced.

Normally, a shallow, fast-flowing river, White Cart Water is prone to flash-flooding and water levels can rise by 6m after only 12 hours of rain. During peak storms, the flow controls hold back the White Cart Water and its tributaries, Earn Water and Kittoch Water, causing the storage areas to flood. Water is released downstream at a controlled rate so that it does not overspill new flood defences being constructed in the city.


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