Tag Archives: Hurricane Sandy

After Matthew: Putting a Value on Natural Coastal Defenses

As coastal communities in the U.S. continue to clear up and count the costs following Hurricane Matthew, we already know things could have been much worse. So, had the storm not weakened and veered off into the Atlantic but made direct landfall as a major hurricane would the infrastructure and coastal defenses along the south-east coast of the U.S. have held up? Or could we have been better prepared? One element often overlooked is that of natural coastal defenses, such as salt marshes and wetlands.

While it’s still early days, it’s clear these natural ecosystems played a role in shielding Georgia and the Carolinas from some of the damage that Matthew inflicted. We can see these effects in the details of our reconstructions of Matthew’s storm surge footprint, but also because of some related research we’re publishing just today that for the first time puts an actual economic value on the protective effect of natural coastal defenses.

Matthew’s surge was greater than 6 feet (1.8m), according to the National Weather Service, when it made landfall about 55km northeast of Charleston on October 8 as a Category 1 storm. Wetlands – such as those around Savannah and Charleston – would have taken the brunt, slowing down the force of the water and offering urban areas some protection against inundation from the sea. Because of the new study we’re now able to express the value of this protection in dollars.

Hurricane Sandy flooding

The study, Coastal Wetlands and Flood Damage Reduction was led by the University of California, Santa Cruz, The Nature Conservancy, and the Wildlife Conservation Society in partnership Guy Carpenter, Lloyd’s, and RMS. We contributed cutting-edge modeling expertise. The research looks back to Hurricane Sandy, which hit New York and New Jersey particularly hard in 2012, although its effect was felt across large swathes of the Eastern Seaboard. The study concluded that:

  • Over $625m in property damage was avoided, with coastal wetlands providing a 10% reduction in property damages across states on average;
  • In New Jersey, wetlands prevented an estimated $425m in losses;
  • The protective value of wetlands during Sandy was nearly 30% in Maryland.

Although the protections offered by features such as wetlands, salt marshes and barrier reefs are already captured by RMS catastrophe models, this was the first time we’d extracted, isolated and measured their unique role. This capacity to better understand and quantify the economic value of natural defenses is a critical tool for policymakers, conservationists and the insurance industry, particularly in regions where wetlands are being degraded.

At RMS we anticipate that macro trends, such as sea level rise, will inevitably elevate the role of natural wetlands in the future. While the jury is still out on how climate change will impact the frequency and severity of hurricanes in the North Atlantic, the Intergovernmental Panel on Climate Change (IPCC) anticipates we will see more weather extremes by the end of the century.

In its 2013 report the IPCC predicted that it was “more likely than not” that the number of the most intense storms will increase in certain parts of the world. And even without any significant change in windstorm severity, sea level rise can be expected to drive up coastal storm losses.

According to Risky Business: The Economic Risks of Climate Change in the United States, a 2014 initiative led by former New York Mayor Michael Bloomberg and former U.S. Treasury Secretary Henry Paulson (and supported by RMS modeling), higher sea levels combined with storm surge will increase the average annual cost of coastal storms along the Eastern Seaboard and the Gulf of Mexico by $2 billion to $3.5 billion in just 15 years.

Better understanding the financial benefits of natural coastline features will ultimately help communities build greater resilience to future storms and floods and to attract more funding for sea defense conservation and restoration. The necessary response may be driven by science and gradual sea level rise. Or it may come only after major catastrophes have done their damage in the future.

Rising Storm Surge Losses in the U.S. Northeast

Co-authored by Anaïs Katz and Oliver Withers, analysts, Capital Market Solutions, RMS

A recent article in Nature Communications, picked up by the BBC, identified a record mean sea-level rise of 5” (127mm) along the coastline north of New York City during 2009-10. Sea levels fluctuate between years; a swing of this size, however, was unprecedented.

This extreme rise in 2009-2010 has been attributed to the downturn of a major current called the Atlantic meridional overturning circulation (AMOC). As changes to sea levels are sensitive to multiple factors, there is volatility around this increase. The AMOC is one of the ocean’s dynamics that is known to have greatly changed over time. It has been shown that weakening and variation of the AMOC is linked to increases of greenhouse gas emissions.

Sea level rise is one of the most tangible and certain consequences of a warmer climate. Climate models suggest that even if greenhouse gas emissions were reduced sea levels will continue to increase. Such a dramatic fluctuation, as seen in 2009-10, highlights the potential for significantly elevated storm surge risk in the region and raises the question what will the impact of future long-term sea-level rise have on storm risk.

A study by Kopp et al. has attempted to predict probability bands for sea rise. The figure below shows the distribution of expected sea-level rise at New York City’s Battery Park throughout the 21st century. The 50th percentile projection of sea level rise is represented as the red line in the figure. Also shown are the maximum rises in sea levels associated with previous hurricane storm surges.

Based on RMS’ estimate of the impacts from hurricanes on residential and commercial property in the Northeast US (from New Jersey north), the 2010 estimate of storm surge contribution to hurricane losses is about 10%. Even where the activity of hurricanes does not change, sea level rise will increase the damage associated with hurricane storm surges. Based on Kopp’s estimates of sea level rise, by 2100 surge losses would contribute about 25% of total hurricane losses.

The largest recent hurricane loss occurred on October 29th 2012, when Superstorm Sandy made landfall near Atlantic City, NJ. Based on the RMS best loss estimate, Sandy caused insured losses between $20 and $25 billion, with much of the damage due to storm surge, not wind.

In terms of a simple extreme value analysis, the storm surge caused by Superstorm Sandy combined with the tide at New York City’s Battery Park was approximately a 1-in-450 year return period for that location. Based on sea level rise alone, this surge and tide combination at this location would move closer to a 1-in-100 year event by the end of the century. The figure below shows the return periods for a storm surge as high as Sandy’s occurring at New York City’s Battery Park, under different sea-level assumptions.

A direct result of increasing amounts of greenhouse gases in the atmosphere will be an increase in sea surface temperatures. While increased sea surface temperatures are likely to cause changes to the activities and intensities of hurricanes, there is no consensus among climate modelers as to the magnitude and direction of these changes. For this reason, the figure below does not consider potential changes in hurricane activity, but focuses solely on sea-level rise, for which there is much more of a general agreement.

While the impacts of climate change remain much debated, changes in loss potential will have material effects on the risk to insurers. With the appreciation of the significance of climate change coming to the fore, the next decades will pose a research challenge for the insurance industry, as to how to incorporate evidence for changes in the level of risk.

This post was co-authored by Anaïs Katz and Oliver Withers. 

Anaïs Katz

Analyst, Capital Market Solutions, RMS
As a member of the advisory team within capital market solutions, Anaïs works on producing capital markets’ deal commentary and expert risk analysis. Based in Hoboken, she provides transaction characterizations to clients for bonds across the market and supports the deal team in modeling transactions. She has woked on notable deals for clients such as Tradewynd Re and Golden State Re. Anaïs has also helped to model and develop her group’s internal collateralized insurance pricing model that provides mark to market prices for private transactions. Anaïs holds a BA in physics from New York University and an MSc in Theoretical Systems Biology and Bioinformatics from Imperial College London.

New Storms, New Insights: Two Years After Hurricane Sandy

When people think about the power of hurricanes, they imagine strong winds and flying debris. Wind damage will always result from hurricanes, but Hurricane Sandy highlighted the growing threat of storm surge as sea levels rise.

While Sandy’s hurricane-force winds were not unusual, the storm delivered an unprecedented storm surge to parts of the Mid-Atlantic and Northeast U.S. In total, Sandy caused insured losses of nearly $20 billion in the U.S., 65 percent of which resulted from surge-driven coastal flooding.

Considering the hazard and severity of the event, we used Sandy as the first real opportunity to validate our hydrodynamic storm surge model, which we released in 2011 and embedded in the RMS U.S. Hurricane Model. We verified the model against more than 300 independent wind and flood observations, the Federal Emergency Management Agency’s (FEMA) 100-year flood zones, and the FEMA best surge inundation footprint for New York City. The model captured the extent and severity of Sandy’s coastal flooding exceptionally well.

We also conducted extensive analysis of claims data from Sandy, which involved reviewing nearly $3 billion in location-level claims and exposure data across seven lines of business, provided by several companies. The purpose of the study was to deepen our understanding of the impacts of flooding on coastal exposures, particularly for commercial and industrial structures.

What struck us was how vulnerable buildings are to below-ground flooding. In many cases, damage to ground- and basement-level property and contents contributed a much higher proportion of the overall losses than expected, particularly for commercial structures in New York’s central business districts.

This insight has prompted us to improve the flexibility of how losses are modeled for contents and business interruption, specifically for basements. Early next year, we will release an update to our flagship North Atlantic Hurricane Models to provide the most-up-to-date view of hurricane risk with new vulnerability modeling capabilities based on insights gained from Sandy.

The model update includes new location-specific content triggers to enable users to make business interruption loss projections dependent on either contents or building damage, rather than on building damage alone. The model also allows users to assess the impact of multiple basement levels in a building, as well as the total value of contents stored within.

The claims data analysis also highlighted the importance of using high-resolution data to model high-gradient perils, such as coastal flooding. Flood losses are extremely sensitive to the locations of coastal exposures, as well as the surrounding topographical and bathymetrical features. Using high quality data with location-level specificity across a variety of building characteristics, as well as a high-resolution storm surge model that can accurately capture the flow of water around complex coastlines and local terrain, minimizes uncertainty.

At this time, RMS remains the only catastrophe modeling firm to integrate a hydrodynamic, time-stepping storm surge model into its hurricane models to represent the complex interactions of wind and water throughout a hurricane’s life-cycle, and we continue to implement lessons learned from new storms.