Wetlands & nature reserve

Blue-Green Cities

Prof Colin Thorne

School of Geography, University of Nottingham

February 2013 to April 2016

Aim: The aim of the project is to develop new strategies for managing urban flood risk as part of wider, integrated urban planning intended to achieve environmental enhancement and urban renewal in which multiple benefits of Blue-Green Cities are rigorously evaluated and understood.


  • Put competent authorities, businesses and communities at the centre of the research by establishing feedback pathways between them and the urban flood risk management modellers, planners and decision makers to ensure co-production of knowledge.
  • Model existing flood risks using coupled surface / sub-surface hydrodynamic models linked to semi-quantitative assessments of sediment/debris dynamics and habitats, using fieldwork where necessary to fill knowledge gaps in urban drainage network forms and functions.
  • Identify and assess options for adaptive strategies combining hard (grey) and soft (green) responses to flood risk that are capable of functioning as spatially-integrated, urban flood risk management systems.
  • Use fieldwork to identify and understand the behavioural responses of individual and institutional stakeholders to urban flood risk management options. Determine the preferences of residents, communities and institutional stakeholders towards Blue-Green assets and the perceived benefits that they can provide.
  • Develop a ‘Flood Footprint’ tool to measure the total socio-economic impact that is directly and indirectly caused by a flood event, and use this to assess the reduction in damages associated with the use of Blue-Green infrastructure for flood risk management.
  • Develop a framework to characterise the uncertainties and barriers to widespread implementation of Blue-Green infrastructure to aid decision making under uncertainty.
  • Develop a GIS tool to evaluate a range of benefits of Blue-Green infrastructure under flood/non-flood conditions and determine the spatial distribution of benefits, benefit trade-offs and dependencies, and the associated beneficiaries

Main project outcomes:

The development of a GIS Multiple Benefits Toolbox (free to download from the Blue-Green Cities website) that can help practitioners understand the relevant dominant benefits, and spatial distribution of benefits, that accrue from Blue-Green infrastructure schemes.

A hydrodynamic model (CityCAT) that represents pluvial and fluvial flood inundation in urban areas, offering full coupling between surface and subsurface (in sewer network) flow, for the first time linking gullies/drains and sewer pipes, and modelling the movement of water through Blue-Green features (e.g. blue-green roofs, retention ponds, permeable paving, swales, water butts), demonstrating that Blue-Green infrastructure can reduce local and downstream flood risk.

A new framework to characterise the uncertainties and barriers to widespread implementation of Blue-Green infrastructure and identification of strategies to overcome the physical science and socio-political barriers.

The establishment of the Newcastle Learning and Action Alliance that brings together professional stakeholders to create a joint understanding of flood and water management problems and negotiate possible solutions, opening communication channels and creating opportunities for collaborative working to achieve common goals and potential for joint funding.

A 2D hydro-morphodynamic model to predict flow and suspended sediment dynamics in urban rivers and investigate how restored floodplains and SuDS ponds can attenuate the upstream flood peak and impact downstream flood risk.

Detailed understanding of how Blue-Green infrastructure treats fine sediment and key urban pollutants during multiple rainfall-runoff events, focussing on detention efficiency and resuspension of sediment (which has implications for maintenance of Blue-Green assets).

Increased understanding of people’s perceptions of Blue-Green infrastructure and the multiple benefits that they prioritise.

The development of a flood footprint damage accounting framework to measure the total socio-economic impact that is directly and indirectly caused by a flood event.


Multiple Benefits GIS Toolbox and Toolbox Guidance