Research: Billions Spent on Flood Damages


In a new study conducted by Stanford University, researchers found that the United States has spent nearly $199 billion in flood damages over the last three decades.

However, researchers went a step further than just comprising a spending report and further indicated that the flooding experienced from 1988 to 2017 as a result of intensifying precipitation—consistent with predictions of global warming—was responsible for one-third ($75 billion) of the total financial costs.

The research was published last week in the journal Proceedings of the National Academy of Sciences and is reported to have helped resolve a long-standing debate about the role of climate change in the rising costs of flooding and provides new insight into the financial costs of global warming overall.

“The fact that extreme precipitation has been increasing and will likely increase in the future is well known, but what effect that has had on financial damages has been uncertain,” said lead author Frances Davenport, a Ph.D. student in Earth system science at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “Our analysis allows us to isolate how much of those changes in precipitation translate to changes in the cost of flooding, both now and in the future.”

Climate Change vs. Socioeconomic Factors

To settle the debate of how much climate change has actually contributed to the rising financial costs of flooding—the most common, widespread, and costly natural hazards—researchers looked at socioeconomic factors like population growth, housing development and increasing property values, in addition to correlations between precipitation and flood damages.

Previously, the university noted that other studies focused either on very detailed case studies or just participation correlations.

“Previous studies have analyzed pieces of this puzzle, but this is the first study to combine rigorous economic analysis of the historical relationships between climate and flooding costs with really careful extreme event analyses in both historical observations and global climate models, across the whole United States,” said senior author and climate scientist Noah Diffenbaugh, the Kara J Foundation Professor at Stanford Earth.

To start, researchers looked at higher resolution climate and socioeconomic data where they applied advanced methods from economics to quantify the relationship between historical precipitation variations and historical flooding costs. The research team also looked at methods from statistics and climate science to evaluate the impact of changes in precipitation on total flooding costs.

As a result, the analyses showed that not only did climate change contribute substantially to the growing cost of flooding in the U.S., but that if the nation were to exceed the levels of global warming agreed upon in the United Nations Paris Agreement, the effects would only grow and continue to worsen.

Diffenbaugh continued, “By bringing all those pieces together, this framework provides a novel quantification not only of how much historical changes in precipitation have contributed to the costs of flooding, but also how greenhouse gases influence the kinds of precipitation events that cause the most damaging flooding events.”

To further isolate changing precipitation as the primary root of increased national flooding, researchers developed an economic model based on observed precipitation and monthly reports of flood damage. In their model, researchers controlled other factors that might affect flooding costs like increases in home values, and then calculated the change in extreme precipitation in each state over the study period. As a result, the team was then able to use the model to determine what the economic damages would have been if those changes in extreme precipitation had not occurred.

“This counterfactual analysis is similar to computing how many games the Los Angeles Lakers would have won, with and without the addition of LeBron James, holding all other players constant,” said study co-author and economist Marshall Burke, an associate professor of Earth system science.

Through this framework, the team found that changes in precipitation accounted for 36% of the actual flooding costs that occurred in the U.S. from 1988 to 2017 and was primarily driven by increases in extreme precipitation.

“What we find is that, even in states where the long-term mean precipitation hasn’t changed, in most cases the wettest events have intensified, increasing the financial damages relative to what would have occurred without the changes in precipitation,” said Davenport.

Moving forward, the research team hopes that their approach can be used in observing other types of natural hazards and climate impacts against different sectors of the economy and to other regions of the globe to help understand the costs and benefits of climate adaptation and mitigation actions.

“That these results are as robust and definitive as they are really advances our understanding of the role of historical precipitation changes in the financial costs of flooding,” Diffenbaugh said. “But, more broadly, the framework that we developed provides an objective basis for estimating what it will cost to adapt to continued climate change and the economic value of avoiding higher levels of global warming in the future.”

Fighting Floods

In wake of increased storms, flooding and climate change reports, many communities and local governments are preparing to protect their coastlines. Most recently, in October, New York City Mayor Bill de Blasio and Gov. Andrew Cuomo announced the kickoff of a $336 million coastal resiliency project.

The news arrived nearly eight years after Hurricane Sandy battered waterfront communities in the Rockaways and across other parts of the city.

According to reports, the shorefront project involves the construction of six miles of storm surge flood protection along the Queens waterfront. However, the first phase of the project will see the building out and restoration of nearly 20 stone groin structures—similar to rock jetties—into the ocean to prevent additional sand erosion.

The rehabilitation and construction of these flood barriers are expected to provide stabilization for a re-nourished sand beach and dune and maintain the protective beach profile, as well as help to restore local ecosystems and ensure the long-term viability of endangered species.

Following these efforts, crews intend to reinforce a network of dunes with stone and steel sheet pile walls, achieving a height two feet higher than the original structure, and further protecting the coast from wave breaking pressure. The new structures are also slated to limit surge inundation and cross-peninsula flooding.

Suffolk County's H&L Contracting LLC will lead construction on the first portion, under a $114 million contract, while an additional $237 million plan to build berms and floodwalls in Jamaica Bay is still in the design process.

The project is slated to reach completion by 2024.

Around the same time, the United States Army Corps of Engineers and the Texas General Land Office released a second draft of its envisioned multi-billion-dollar coastal storm barrier, Ike Dike. Plans for the barrier have reportedly been in the works since Hurricane Ike rocked Galveston, Texas, in 2008, and are expected to cost anywhere between $23 billion to $32 billion.

According to the Corps, the project has the potential to save the state $2.28 billion annually in storm-associated recovery costs, noting that Hurricane Ike caused $38 billion dollars in damages alone.

Noting on the project’s revisions, one of the biggest changes involves the replacement of a series of levees and floodways previously slated to run parallel to State Highway 87 on Bolivar Peninsula and FM 3005 on Galveston Island with 43 miles of a natural dune and beach system.

The system is reportedly comprised of 14-foot dunes on the landward side and 12-foot dunes on the Gulf, followed by 250 of beach. While the Corps notes that the change will reduce environmental and social impacts, it would also require about 39 million cubic yards of sand for beach and dune construction on both Bolivar Peninsula and West Galveston Island.

Other changes to the project proposal involve updating the storm surge gate between Galveston and Bolivar Peninsula to two 650-foot wide surge gates at the mouth of Galveston Bay, instead of the initially proposed 1,200-foot wide gate. Although the change would reduce the water flow by 10%, the Corps estimates that design change has less of an impact on restricting the flow of water between the bay and the Gulf than previously proposed, adding that the gates would only be closed during the event of a storm.

Another major revision to the coastal protection system is what the Corps call a “ring barrier system.” The system is comprised of 14-foot-high floodwalls and gates surrounding a 15-mile stretch of Galveston Island’s backside. The updated version also recommends increasing the height of an 8-mile stretch of the existing Galveston Seawall to 21 feet.

If approved, the Ike Dike barrier project is estimated to take between 12-20 years for design completion and construction.

At the end of September, Representatives David E. Price (D-North Carolina) and Lee Zeldin (R-New York) introduced legislation aimed at reducing the impacts of severe weather, such as tropical storms, hurricanes, flooding and other risks associated with rising sea levels.

The bipartisan bill is entitled the Flood Resiliency and Taxpayer Savings Act of 2020.

According to the bill’s summary, the legislation represents a pragmatic approach to enhancing the safety of federal investments and communities, while building and rehabilitating in flood-prone areas. Similar to other construction legislation, the bill directs federal agencies to plan for potential future risks (excluding the military with the exception of the U.S. Army Corps of Engineers) in order to augment longstanding flood review processes.

The legislation arrives as the National Oceanic and Atmospheric Administration reported that flooding has been named as the most common and expensive natural disaster in America, costing the nation more than $845 billion in estimated losses from flood- and hurricane-related disasters since 2000.

The Administration adds that in wake of these disasters, the federal government often pays most of the repair costs, while losses from recent disasters underscore the need for a cost-effective disaster risk management strategy to safeguard the nation’s infrastructure, protect businesses and communities, and conserve taxpayer resources.

The bill recognizes the uncertainty of flood mapping and calls for using additional available information on how flood risks may change over the lifetime of potential projects.

Specifically, the legislation:

  • Directs federal agencies to consider and plan for future flood risk as they evaluate spending federal dollars, including the entire lifespan of a project;
  • Requires agency leaders, for projects that are currently or in the future will be in floodprone areas, to use the best available data about current and future flood risk including FEMA maps, state and local data, hydrologic studies, and other information; and
  • In the absence of concrete data about future flood risk, it ensures that agencies incorporate appropriate safeguards to shield communities (and federal investment) from future damage and loss—such as structure elevation, hardening, nature-based systems, or other mitigation and resiliency strategies.

If implemented, the Flood Resiliency and Taxpayer Savings Act places the responsibility with the Federal Interagency Floodplain Management (FIFM) Task Force—which is chaired by the Federal Emergency Management Agency—and requires FIFM to consult with states, localities, tribes and other stakeholders.

Additionally, FIFM will also issue guidelines to federal agencies for implementation of new protections and periodic reports to Congress on the implementation of the guidelines, including recommendations for improvements to enhance resilience and the protection of federal investments.



Tagged categories: Climate monitoring; Colleges and Universities; Environmental Controls; Flood Barrier; Infrastructure; NA; North America; Research; Research and development; Water/Wastewater

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