Glasgow City Council - Surface Water Management Programme

Sweco were commissioned by Glasgow City Council to undertake a Surface Water Management Programme for masterplan areas in South Dalmarnock and Cumbernauld. The scope of the programme was to manage surface water flood risk and allow the council to satisfy their duties under the Flood Risk Management (Scotland) Act (2009).

Key Facts

Client – Glasgow City Council
Location – Scotland
Fee Value – £650k

Project

Sweco undertook a programme of works with multiple Surface Water Management Plans (SWMP) and Sustainable Drainage Systems (SuDS) designs for masterplan areas in South Dalmarnock and Cumbernauld.

The scope of feasibility and outline designs included site appraisal, catchment and hydrological assessment, schematic/feasibility option design, public consultation and engagement, option assessment (including economic, hydraulic and multi-criteria), and implementation planning.

Detailed design entailed further hydraulic and technical/buildability assessment, design refinement, and production of final designs and specifications, including implementation schedules and maintenance regimes. 

Sweco were responsible for the delivery of all elements of the projects through to the implementation of solutions.

Approach

Our approach to the SWMP delivery commenced with the identification of surface water flood hotspots and pathways. This was obtained as an outcome of integrated catchment modelling (using Infoworks ICM-2D) to consider pluvial, network, fluvial and tidal flood risk.

The optioneering was undertaken to account for the differences in targeted level of service (LoS) provision between the sewer provider (Scottish Water) who typically sought a 30 year LoS and the local authorities who sought a minimum a 50 year LoS with climate change. Our approach also considered wider catchment management objectives to facilitate future development objectives. Using GIS analysis we produced flood risk, flow velocity and hazard maps including assessments of asset vulnerability, employing the DEFRA Multi-Coloured Handbook approach to estimate flood damages both with and without the impact of climate change.

Development for the Cockenzie Street SWMP was constrained by the need to avoid inducing or worsening flood risk elsewhere either by over-throttling at the upstream end of the study area or increasing the conduction capacity of the combined sewer and surface water/watercourse networks through the study area. Option development focussed on local attenuation, storage and flowpath alteration, including surface water separation from the combined sewer through provision of SuDS treatment trains for local road and roof runoff.

The SWMP developed for Cockenzie Street established the requirements for achieving a 30 year LoS for the combined sewer system that included for the benefit of regular jetting of the sewer networks. By throttling the Camlachie Burn and raising an embankment we designed a sacrificial flood storage area within publicly owned parkland that provided a cost-effective management option capable of achieving a 50 year LoS against surface water flood risk. Additional surface water separation / SuDS provision options were assessed and we undertook landscape architecture design to integrate the sustainable drainage features into the streetscape and parkland.

At South Dalmarnock, Sweco produced an integrated strategic drainage infrastructure plan to allow for the development of the masterplan area, which covered 1 km2 of derelict heavy industrial land, including the site of the former Dalmarnock Power Station. The solution design addressed site drainage requirements utilising green networks as well as the regeneration of the site, adjacent to the River Clyde, for a 200 year LoS with climate change.

An innovative terraced ‘flood finger’ river interface was designed, capable of mitigating the loss of floodplain storage caused by the redevelopment, whilst also providing an aesthetically appealing and creative flood defence to the site itself. Several consultation and stakeholder meetings were held, including customer engagement to provide feedback on our designs.

Solution

The solutions that we implemented included culvert daylighting, enhancement of public greenspace and the creation of additional capacity in existing watercourses, stormwater and combined sewers to facilitate future development and public amenity benefits without the requirement for disruptive sewer upgrades.

At Cumbernauld, Sweco developed a SuDS solution that encompassed detailed site assessment, utility constraint assessment, design and modelling of SUDS, excavation works, and landscaping. The design utilised an innovative and aesthetically appealing “cascading pond” which is the largest SUDS detention pond solution in Europe at 22,000 m3 total capacity. The scheme realised savings of approximately £2m and achieved an excellent 88% technical governance score.

Subsequent to this commission Sweco have been engaged to undertake feasibility SWMPs and detailed designs for a further 7 sites in the Glasgow area. The work has a capital budget of £15m.

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