Sustainable Drainage Policies for Water Security
Summary
London developed the Sustainable Drainage Policy as a cost-effective solution to the urban flooding problems caused by the city's antiquated drainage system from the 1800s.
London's drainage and sewerage infrastructure was developed in the 1800s and built to serve 2 million people. Today, London's population is around 9 million. The city's increased population and further development put significant stress on the antiquated system. The number of roadways and impervious surfaces throughout the city increases the overall runoff and clogs the drainage system. Even mild events such as light rainfall can cause flooding and, relatedly, water quality issues for the entire city. Due to the interconnected nature of London's stormwater and wastewater systems, toilets and showers can become backed up with sewage, which poses various public health risks. With such a large population, London struggles to function on a combined sewer system.
The 2007 London Flood Risk Appraisal identified a high potential risk for severe flooding in the city. In fact, in 2007 and 2008, other areas in England suffered from severe flooding events that caused severe infrastructural damages in the surrounding cities. These flooding events outside of London prompted the city to develop new plans focusing on stormwater and flood management. In addition to flooding, drought is of significant concern for the city. Thus, measures to foster resilience to both flooding and drought are needed. The London city government created policy "5.13 the Sustainable Drainage Policy" under the Flood and Water Management Act to address the increased risk of floods, in addition to developing a means of water storage.
Intervention
The Sustainable Drainage Policy within the greater London Plan incentivizes large-scale developers to implement sustainable urban drainage systems (SuDS) during development. This policy promotes SuDS by prioritizing management strategies such as rainwater storage or infiltration techniques, thus reducing the water discharged into the combined sewer (Sustainable Drainage in London, 2016). The interventions (in order of priority) are as follows:
1. Store rainwater for later use;
2. Use infiltration techniques, such as porous surfaces in non-clay areas;
3. Attenuate rainwater in ponds or open water features for a gradual release;
4. Attenuate rainwater by storing in tanks or sealed water features for a gradual release;
5. Discharge rainwater direct to a watercourse;
6. Discharge rainwater to a surface water sewer/drain; and
7. Discharge rainwater to the combined sewer.
It is important to note that the Sustainable Drainage Policy mentions that these drainage measures should yield co-benefits when combined with policies within the greater London Plan, such as water use efficiency, biodiversity, and recreation (Ossa-Moreno et al., 2017). The Sustainable Drainage Policy intervention list has been updated slightly for the new London Plan (set to be released in summer 2020). The Sustainable Drainage Action Plan complements this policy by highlighting the necessity of retrofitting the current infrastructure (Chapter 9 Sustainable Infrastructure, 2017; Greater London Authority, 2016). This emphasis on retrofitting is particularly important when large-scale financing for new projects (e.g., new pipelines, roadways, treatment facilities) is not available. Thus, the city utilizes planned upgrades of infrastructure and systems to transition the city towards sustainable drainage, one upgrade at a time. Not only does this benefit the overall sustainable drainage mission, but it creates an economic incentive for businesses or individuals who use large amounts of non-potable water. The additional cost in implementing these systems during upgrades or maintenance is marginal and has potential cost savings.
Challenges
The cost and time needed to integrate SuDS at the beginning of a design process can deter businesses and developers. Additionally, in areas where SuDS are needed (e.g., urban centers, high-density areas, etc.), the cost of implementation is higher due to the impermeable surfaces and infrastructure present, reiterating the necessity of strategically implementing SuDS during planned infrastructure upgrades.
Outcomes
Through the Sustainable Drainage Policy and the complementary Sustainable Drainage Action Plan, London has developed the Strategic SuDS Pilot Program, which addresses the difficulties that face flood management authorities when requesting central government funding for flood prevention through the current schemes. Additionally, funding for SuDS is included in local implementation plans funded through Transport for London in addition to other sustainable city schemes (Transport for London, 2016). Projects that have implemented SuDS have seen diminished stormwater runoff. Renfrew Close in East London underwent sustainable drainage revamp and now experiences drainage delays between 12-14 hours. Crown Woods Way implemented two rain garden basins that allow for 30% more water to reach the subsurface compared to a regular lawn. Overall, the number of areas across London that will be able to withstand a 100-year flooding event has increased (Davis & Naumann, 2017; Susdrain, n.d.). In Lamb Drove, Cambridge, the implementation of SuDS within a residential area (including permeable pavement, green roofs, and detention basins) has a cost savings of around £11,000 per year. There is an additional cost-saving per household of £30 per year due to the reduction in stormwater disposal (Susdrain, n.d.).
References
Sustainable Drainage Policies for Water Security
Summary
London developed the Sustainable Drainage Policy as a cost-effective solution to the urban flooding problems caused by the city's antiquated drainage system from the 1800s.
London's drainage and sewerage infrastructure was developed in the 1800s and built to serve 2 million people. Today, London's population is around 9 million. The city's increased population and further development put significant stress on the antiquated system. The number of roadways and impervious surfaces throughout the city increases the overall runoff and clogs the drainage system. Even mild events such as light rainfall can cause flooding and, relatedly, water quality issues for the entire city. Due to the interconnected nature of London's stormwater and wastewater systems, toilets and showers can become backed up with sewage, which poses various public health risks. With such a large population, London struggles to function on a combined sewer system.
The 2007 London Flood Risk Appraisal identified a high potential risk for severe flooding in the city. In fact, in 2007 and 2008, other areas in England suffered from severe flooding events that caused severe infrastructural damages in the surrounding cities. These flooding events outside of London prompted the city to develop new plans focusing on stormwater and flood management. In addition to flooding, drought is of significant concern for the city. Thus, measures to foster resilience to both flooding and drought are needed. The London city government created policy "5.13 the Sustainable Drainage Policy" under the Flood and Water Management Act to address the increased risk of floods, in addition to developing a means of water storage.
Issue
Intervention
The Sustainable Drainage Policy within the greater London Plan incentivizes large-scale developers to implement sustainable urban drainage systems (SuDS) during development. This policy promotes SuDS by prioritizing management strategies such as rainwater storage or infiltration techniques, thus reducing the water discharged into the combined sewer (Sustainable Drainage in London, 2016). The interventions (in order of priority) are as follows:
1. Store rainwater for later use;
2. Use infiltration techniques, such as porous surfaces in non-clay areas;
3. Attenuate rainwater in ponds or open water features for a gradual release;
4. Attenuate rainwater by storing in tanks or sealed water features for a gradual release;
5. Discharge rainwater direct to a watercourse;
6. Discharge rainwater to a surface water sewer/drain; and
7. Discharge rainwater to the combined sewer.
It is important to note that the Sustainable Drainage Policy mentions that these drainage measures should yield co-benefits when combined with policies within the greater London Plan, such as water use efficiency, biodiversity, and recreation (Ossa-Moreno et al., 2017). The Sustainable Drainage Policy intervention list has been updated slightly for the new London Plan (set to be released in summer 2020). The Sustainable Drainage Action Plan complements this policy by highlighting the necessity of retrofitting the current infrastructure (Chapter 9 Sustainable Infrastructure, 2017; Greater London Authority, 2016). This emphasis on retrofitting is particularly important when large-scale financing for new projects (e.g., new pipelines, roadways, treatment facilities) is not available. Thus, the city utilizes planned upgrades of infrastructure and systems to transition the city towards sustainable drainage, one upgrade at a time. Not only does this benefit the overall sustainable drainage mission, but it creates an economic incentive for businesses or individuals who use large amounts of non-potable water. The additional cost in implementing these systems during upgrades or maintenance is marginal and has potential cost savings.
Challenges
The cost and time needed to integrate SuDS at the beginning of a design process can deter businesses and developers. Additionally, in areas where SuDS are needed (e.g., urban centers, high-density areas, etc.), the cost of implementation is higher due to the impermeable surfaces and infrastructure present, reiterating the necessity of strategically implementing SuDS during planned infrastructure upgrades.
Outcomes
Through the Sustainable Drainage Policy and the complementary Sustainable Drainage Action Plan, London has developed the Strategic SuDS Pilot Program, which addresses the difficulties that face flood management authorities when requesting central government funding for flood prevention through the current schemes. Additionally, funding for SuDS is included in local implementation plans funded through Transport for London in addition to other sustainable city schemes (Transport for London, 2016). Projects that have implemented SuDS have seen diminished stormwater runoff. Renfrew Close in East London underwent sustainable drainage revamp and now experiences drainage delays between 12-14 hours. Crown Woods Way implemented two rain garden basins that allow for 30% more water to reach the subsurface compared to a regular lawn. Overall, the number of areas across London that will be able to withstand a 100-year flooding event has increased (Davis & Naumann, 2017; Susdrain, n.d.). In Lamb Drove, Cambridge, the implementation of SuDS within a residential area (including permeable pavement, green roofs, and detention basins) has a cost savings of around £11,000 per year. There is an additional cost-saving per household of £30 per year due to the reduction in stormwater disposal (Susdrain, n.d.).
Issues |
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Water Infrastructure and Technology |
Solutions |
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Infrastructure & System Improvements |
References
Chapter 9 Sustainable Infrastructure (The Draft London Plan). (2017). https://www.london.gov.uk/sites/default/files/draft_london_plan_chapter_9.pdf
Davis, M., & Naumann, S. (2017). Making the Case for Sustainable Urban Drainage Systems as a Nature-Based Solution to Urban Flooding. In N. Kabisch, H. Korn, J. Stadler, & A. Bonn (Eds.), Nature-Based Solutions to Climate Change Adaptation in Urban Areas: Linkages between Science, Policy and Practice (pp. 123–137). Springer International Publishing. https://doi.org/10.1007/978-3-319-56091-5_8
Greater London Authority. (2016). London Sustainable Drainage Action Plan. https://www.london.gov.uk/sites/default/files/lsdap_december_2016.pdf
Susdrain (n.d.). Retrieved August 12, 2020, from https://www.susdrain.org/case-studies/case_studies/index.html
Ossa-Moreno, J., Smith, K. M., & Mijic, A. (2017). Economic analysis of wider benefits to facilitate SuDS uptake in London, UK. Sustainable Cities and Society, 28, 411–419. https://doi.org/10.1016/j.scs.2016.10.002
Sustainable drainage in London. (2016, November 1). London City Hall. https://www.london.gov.uk//what-we-do/environment/climate-change/surface-water/sustainable-drainage-london
Transport for London. (2016). SuDS in London – a guide.