The proverb “It takes a village” has been adopted by many to convey that goals are attained using the collective knowledge of many, rather than few. It may originally have referred to child-rearing, but the concept is applicable to the environment around us.
Coastal regions across the globe are greatly concerned with the risk that rising seas bring. The City of Miami Beach is one such region. As a barrier island in the subtropics sitting just feet above sea level, Miami Beach is at high risk of flooding.
The City of Miami Beach developed a stormwater management plan aimed at combatting flooding by installing improved drainage and new pump systems. The improved and new mitigation systems were designed to protect home and business owners from coastal (storm surge and “King Tides”) flooding as well as floods from heavy rainfall.
A request for proposals was sent to design a business use case analysis that would model the effectiveness of the new stormwater management plan.
Two components of the proposed business use case were to address:
- The economic impact from flooding associated with sea level rise to home and business owners (i.e., cost of inaction) and,
- The reduction of risk post-mitigation and the benefits to home and business owners that would be yielded.
AIR was well-equipped to address both components.
A future scenario published by The Southeast Florida Regional Compact’s Unified Sea Level Rise Projection was adopted by The City of Miami Beach (The City) as the target level at which to model future flood loss. The selected scenario estimated that sea levels would be 1 foot higher by 2050, relative to those in 2013 (Sea Level Rise Work Group 2015).
The goal of this project was to provide The City with the information required to make an informed and economic decision, with the greatest return for those who call it home.
A task of this magnitude required a “village” of experts, however, whose collective knowledge and skills could be applied to it.
Team of Experts
ICF, a global consulting services company, chose AIR to be part of a team that was ultimately selected to answer The City’s call. Other team members included Kimley Horn, an engineering firm with high-resolution hydraulic modeling capabilities; Brizaga, a communications expert; and Florida Atlantic University. ICF provided project leadership and detailed economic modeling expertise.
AIR was tasked with quantifying the cost of inaction to The City, providing a representative “moderate” storm surge footprint from its catalog of events to serve as boundary conditions for Kimley Horn’s hydraulic model, and consuming the model output to quantify the reduction in risk after the implementation of flood defenses. The latter was conducted on a small study area, comprising a two-block neighborhood in southern Miami Beach.
A Novel Approach to Future Storm Surge Risk
AIR anticipated that sea level rise impacted the storm surge footprints within its hurricane model in three ways, by increasing the:
- Number of loss-generating events
- Event intensity (i.e., flood depth)
- Flood inundation footprint
AIR created a buffer encompassing South Florida and considered all hurricane tracks that intersected with it to be potential loss-generating storm surge events in Miami Beach. AIR adopted a unique approach similar to that developed by McInnes et al., 2011, to account for the increased depths and larger footprints associated with surge events under a select sea level rise scenario. This method was not only practical, robust, and computationally efficient, but also leveraged the previously developed damage functions in the AIR Hurricane Model for the United States.
In addition, the catalog of sea level rise–augmented storm surge events could be leveraged for future projects and studies.
The Cost and Benefit of Resilience
The results of The City-wide cost of inaction analysis revealed that a 1 foot increase in sea level rise doubled storm surge average annual loss (AAL), highlighting the importance of taking action, as flood insurance premiums could increase by a similar margin, compounding the impacts of higher loss potential.
More frequent losses (e.g., at the 20-year return period) are poised to increase on a higher percentage compared to the most extreme events. For example, the 20-year return period loss (that with a 5% annual probability of occurrence) is expected to increase by more than 250%.
As storm surge flood depths for even moderate events, such as Category 2 hurricanes, increased by as much as 6 feet, investments in stormwater resilience of up to USD 2 billion—publicly and/or privately funded—yielded a positive impact on home and business owners by preserving or improving property values, and protecting The City’s tax base, as indicated by the macroeconomic modeling analysis carried out by the ICF team.
Combatting Climate Change Risk with a “Village” Approach
The use of catastrophe models in an analysis of this nature, one designed to address future losses using a sea level rise projection, was a novel concept and yielded many benefits. At the highest level, AIR and the greater project team provided the means by which city officials could make the most informed decisions, resulting in the greatest benefit for the citizens of the City of Miami Beach.
In addition, the data-driven methodology developed by AIR to address potential storm surge losses with sea level rise can be used for future projects. Lastly, AIR developed a strong network of partnerships by collaborating with the other experts of their respective industries, many of whom may be partners again in the future.
Putting a price tag on resilience is not a task that AIR can accomplish alone, and this study proved that it does in fact take a “village” to combat climate change risk, ensuring that no one needs to weather the storm alone.