Modelling the benefits of dispersed SUDS for flood risk reduction and the management of urban draina...

<p>Greater Manchester Combined Authority (GMCA) is seeking technical support to design and model the benefits of nature based Sustainable Drainage Systems (hereafter SuDS) retrofit for a pilot area. The technical support team will develop and deliver a costed, green SuDS retrofit design for a discrete pilot area and model the impacts on the (1) predicted surface water flood risk extent and properties at risk and (2) the quantity of surface water entering the combined sewer system and sewer flood risk. Building climate resilience in Greater Manchester is one of the priorities of the Greater Manchester 5-Year Environment Plan and the Greater Manchester Strategy. SuDS offer solutions to urban challenges such as surface water flood risk, increasing quantities of water entering combined sewer systems and water quality in urban areas, in addition to numerous co-benefits for local urban residents and businesses. The GMCA-led IGNITION project has been working to explore and monetise the benefits of green SuDS retrofit, to inform the development of pipelines of investment in SuDS across Greater Manchester city region. A key barrier to investment in urban green SuDS is convincing those parties who will benefit to invest. To increase investor confidence in the performance of dispersed green SuDS in a discrete geographical area, this commission is for technical support to model the benefits of a dispersed streetscape SuDS retrofit design for a pilot urban area of GM. The retrofit will cover an urban neighbourhood of GM, the exact pilot area will be determined through opportunity mapping currently being undertaken by the IGNITION team initial results suggest this will be no larger than 0.5km2 and likely to be less than 0.25km2. The SuDS design will need to be costed and the priority benefits to be modelled include: (1) the impact on predicted surface water flood risk extents and properties at risk, (2) the impact on hydraulic sewer flooding both internal and external, (3) the impact on combined sewer overflow (CSO) spill frequency, (4) the impact on onward combined sewer pumping and wastewater treatment. The predicted benefits will subsequently be used by the IGNITION team, in combination with wider co-benefits, to provide confidence in the likely financial benefits over costs and develop the case for SuDS investment for target beneficiaries in the water sector.</p>