Spatial evaluation of the multiple benefits of sustainable drainage systems

Malcolm Morgan,Richard Fenner

doi:10.1680/jwama.16.00048

Malcolm Morgan, Richard Fenner

Open Access

https://doi.org/10.1680/jwama.16.00048

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Abstract

Traditional approaches to understanding the multiple benefits of sustainable drainage systems often rely on value transfer. This converts each benefit into a monetary value, which can then be compared with the cost of the project. The approach, while well-developed, is limited because it does not systematically incorporate the spatial nature of the benefits. This paper discusses the development of an alternative way of evaluating and comparing benefits, allowing spatial distribution and local context and circumstances to be taken into consideration. The suggested approach is to create a score for each benefit category, which is normalised against a defined initial condition state on a scale of 0 to 10. This approach allows a direct comparison of the relative magnitude of benefits for a given location and provides a clear understanding of how and to whom multiple benefits accrue. The approach allows a singular significant benefit to be compared against many minor benefits. It can also easily be modified to reflect local preferences by weighting each benefit category appropriately. The method is demonstrated by three case studies in Newcastle, UK.

Highlights

Modern urban environments are impacted by stormwater runoff, exacerbated by increasing frequencies of more severe weather events
The uptake of Sustainable drainage systems (Suds) in many cities remains slow and robust justification for their adoption is often required. This can be achieved by modelling hydraulic performance to demonstrate their effectiveness at mitigating urban flooding (Ahilan et al, 2014) while acknowledging that such blue–green infrastructure (BGI) can deliver an extensive range of other benefits and add to the greening and regeneration of cities
The spatial distributions of the benefits and the benefit profile are shown in Figures 5 and 6, respectively, with Figure 5(b) representing the overall multiple-benefit intensity

Summary

Introduction

Modern urban environments are impacted by stormwater runoff, exacerbated by increasing frequencies of more severe weather events. Traditional solutions carry the water rapidly ‘away’ in pipes and channels, so it accumulates further down an urban catchment, potentially causing more serious flooding problems elsewhere. Managing this runoff locally at its source has been the preferred policy of drainage engineers since the 1990s. The uptake of Suds in many cities remains slow and robust justification for their adoption is often required This can be achieved by modelling hydraulic performance to demonstrate their effectiveness at mitigating urban flooding (Ahilan et al, 2014) while acknowledging that such blue–green infrastructure (BGI) can deliver an extensive range of other benefits and add to the greening and regeneration of cities

Results

Discussion

Conclusion