Global climate models show an increase in extreme climate events which will increase volumes of precipitation – up to 10 per cent by 2050 and up to 20 per cent by 2100.
Associated with growing precipitation magnitude and intensity are increases in runoffs, stormwater discharges, and flooding. Thus, it will affect the performance of urban drainage networks designed for the conditions of the past or present climate.
Municipalities and other stakeholders, therefore, need to have a plan to prepare for these extreme conditions and to adapt infrastructures to withstand these extreme conditions.
The study discusses in detail the literature on adaptation, forms of adaptation strategies and actions, and development of adaptation plans from trial and error approach to sophisticated methods like decision-scaling and robust decision making (RDM). Then there are other adaption strategies like robust optimisation or using real options discussed in the paper.
The study presents a case study of an urban drainage system in Somerville, Massachusetts. The site is highly urbanised, with limited open space, and a high percentage – 75% of its surface is impervious. Researchers chose the site because it is already experiencing the effects of heavy precipitation that causes drainage flooding and combined sewer overflows.
Researchers have conducted vulnerability assessments against possible climate change scenarios, the system’s sensitivities to it, and its adaptive capacity. Adaptation planning involved the development and testing of several sets of alternative and integrating adaptation actions that can manage the impacts over time and space.
In quantifying the economic cost of adaptation, the researchers have used the two decision-making approach: a design storm least-cost approach and a risk-based approach where performance is evaluated on all possible precipitation conditions.
Adaptation strategies chosen for the study includes underground storage, LID (low-impact development) across the watershed, sewer separation, and a combination of sewer separation and LID. LID techniques were available for municipal and homeowners to apply.
The case study of the Somerville drainage system shows that hazardous flood volumes and combined sewer overflow (CSO) discharges exceed the design metrics under present and future climate change scenarios and thus requiring adaptation actions.
Researchers have designed and implemented the case study to reflect the many attributes of an effective climate adaptation, planning process for infrastructure using a drainage system as an example.
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Kirshen, P., Caputo, L., Vogel, R., Mathisen, P., Rosner, A., & Renaud, R. (2014). Adapting Urban Infrastructure to Climate Change: A Drainage Case Study. America Society of Civil Engineers. DOI: 10.1061/ (ASCE)WR.1943-5452.0000443.