Climate change is predicted to cause an increase in the flood risk of a London borough urban sub-catchment investigated in the study.
Flooding is projected to come from a 1-in-5-year storm. Large areas of the urban drainage network that are not at risk of flooding today will soon be at risk in the next 50 years and a possible mix of the blue-green and grey solution is possible to manage the risk, according to the study.
Grey infrastructure refers to the traditional waterway systems like pipe networks, storage tank, and floodwall.
While blue-green infrastructure refers to the infrastructure that aims at restoring the natural water cycle by putting together water management and green infrastructure. An example is a vegetated surface to store and retain excess stormwater.
Researchers Leon Kapetas and Richard Fenner aim to answer the following questions through the study:
- What is the right mix of blue-green and grey infrastructure at any given time and location?
- How do multiple benefits affect the choice of a preferred pathway?
The first question is addressed by applying an adaptation pathways approach at a smaller scale or urban sub-catchment. Solutions or options considered include grey pipe expansion, bio-retention cells, permeable pavements, and storage ponds which are assessed separately and in combination with each other.
The paper applies an adaptation pathways approach to compare a range of alternative options in dealing with current and future flood risks.
Using the standard cost-benefit assessments, comparison of infrastructure costs against monetized multiple-benefits accrued through each option is measured and analyzed through existing tools and models.
The study also offers flexibility to move from one option or pathway to the next as information becomes available with time and as threshold performance are met.
The researchers showed that there is a trade-off between deferring intervention until flood mitigation are needed and delivery of multiple benefits associated with the interventions.
This means that to determine the outcome of the adaptation planning, the multiple pathway assessment process is crucial.
To read the entire study, CLICK on the link below:
Kapetas, L., & Fenner, R. (2020) Integrating blue-green and grey infrastructure through an adaptation pathways approach to surface water flooding. Phil.Trans.R.Soc.A378: 20190204. http://dx.doi.org/10.1098/rsta.2019.0204