Tag Archives: coastal flooding

Friday 13th and the Long-Term Cost of False Alarms

If the prospect of flooding along the East Coast of England earlier this month was hard to forecast, the newspaper headlines the next day were predictable enough:

Floods? What floods? Families’ fury at evacuation order over storm surge … that never happened (Daily Mail)

East coast residents have derided the severe storm warnings as a ‘load of rubbish’ (The Guardian)

Villagers shrug off storm danger (The Times)

The police had attempted an evacuation of some communities and the army was on standby. This was because of warnings of a ‘catastrophic’ North Sea storm surge on January 13 for which the UK Environment Agency applied the highest level flood warnings along parts of the East Coast: ‘severe’ which represents a danger to life. And yet the flooding did not materialize.

Environment Agency flood warnings: January 13 2017

Water levels were 1.2m lower along the Lincolnshire coast than those experienced in the last big storm surge flood in December 2013, and 0.9m lower around the Norfolk towns of Great Yarmouth and Lowestoft. Predicting the future in such complex situations, even very near-term, always has the potential to make fools of the experts. But there’s a pressure on public agencies, knowing the political fallout of missing a catastrophe, to adopt the precautionary principle and take action. Imagine the set of headlines, and ministerial responses, if there had been no warnings followed by loss of life.

Interestingly, most of those who had been told to evacuate as this storm approached chose to stay in their homes. One police force in Essex, knocked on 2,000 doors yet only 140 of those people registered at an evacuation centre. Why did the others ignore the warnings and stay put? Media reports suggest that many felt this was another false alarm.

The precautionary principal might seem prudent, but a false alarm forecast can encourage people to ignore future warnings. Recent years offer numerous examples of the consequences.

The Lessons of History

Following a 2006 Mw8.3 earthquake offshore from the Kurile Islands, tsunami evacuation warnings were issued all along the Pacific coast of northern Japan, where the tsunami that did arrive was harmless. For many people that experience weakened the imperative to evacuate after feeling the three-minute shaking of the March 2011 Mw9 earthquake, following which 20,000 people were drowned by the tsunami. Based on the fear of what happened in 2004 and 2011, today tsunami warnings are being ‘over-issued’ in many countries around the Pacific and Indian Oceans.

For the inhabitants of New Orleans, the evacuation order issued in advance of Hurricane Ivan in December 2004 (when one third of the city’s population moved out, while the storm veered away), left many sceptical about the mandatory evacuation issued in advance of Hurricane Katrina in August 2005 (after which around 1500 drowned).

Agencies whose job it is to forecast disaster know only too well what happens if they don’t issue a warning as any risk looms. However, the long-term consequences from false alarms are perhaps not made explicit enough. While risk models to calculate the consequence are not yet available, a simple hypothetical calculation illustrates the basic principles of how such a model might work:

  • the chance of a dangerous storm surge in the next 20 years is 10 percent, for a given community;
  • if this happens, then let’s say 5,000 people would be at grave risk;
  • because of a recent ‘false’ alarm, one percent of those residents will ignore evacuation orders;
  • thus the potential loss of life attributed to the false alarm is five people.

Now repeat with real data.

Forecasting agencies need a false alarm forecast risk model to be able to help balance their decisions about when to issue severe warnings. There is an understandable instinct to be over cautious in the short-term, but when measured in terms of future lives lost, disaster warnings need to be carefully rationed. And that rationing requires political support, as well as public education.

[Note: RMS models storm surge in the U.K. where the risk is highest along England’s East Coast – the area affected by flood warnings on January 13. Surge risk is complex, and the RMS Europe Windstorm Model™ calculates surge losses caused by extra-tropical cyclones considering factors such as tidal state, coastal defenses, and saltwater contamination.]

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.

Mangroves and Marshes: A Shield Against Catastrophe?

“We believe that natural ecosystems protect against catastrophic coastal flood losses, but how can we prove it?”

This question was the start of a conversation in 2014 which has led to some interesting results. And it set us thinking: can RMS’ models, like the one which estimates the risk of surge caused by hurricanes, capture the protective effect of those natural ecosystems?

The conversation took place at a meeting on Coastal Defenses organized by the Science for Nature and People Partnership. RMS had been invited by one of our leading clients, Guy Carpenter, to join them. The partnership is organized by The Nature Conservancy, the Wildlife Conservation Society, and the National Center for Ecological Analysis and Synthesis.

We were confident we could help. Not only did we think our models would show how biological systems can limit flood impacts, we reckoned we could measure this and then quantify those benefits for people who calculate risk costs, and set insurance prices.

RMS’ modeling methodology uses a time-stepping simulation, which relies on a specialist ocean atmosphere model, allowing us to evaluate at fine resolution how the coastal landscape can actually reduce the storm surge—and in particular lower the height of waves. In many buildings the real weakness proves to be the vulnerability to wave action rather than just the damage done by the water inundation alone.

The first phase of RMS’ work with The Nature Conservancy is focused on coastal marshes as part of a project supported by a Lloyd’s Tercentenary Research Foundation grant to TNC and UC Santa Cruz. Under the supervision of Paul Wilson, in the RMS model development team, and working with Mike Beck who’s the lead marine scientist for The Nature Conservancy, the project is focused on the coastlines, which were worst impacted by the surge from Superstorm Sandy. The irregular terrain of the marsh and resulting frictional effects reduce the surge height from the storm. Our work is showing that coastal marshes can reduce the flood risk costs of properties, which lie inland of the marshes by something in the range of 10-25%.

Tropical Defenses

So, that’s the effect of coastal marshes. But what about other biological defenses such as mangrove forests and offshore reefs (whether coral or oyster reefs)? Further research is planned in 2016 using RMS models to measure those likely benefits too.

But here’s a rather intriguing (if unscientific) thought: is there a curious Gaia-like principle of self-protection operating here in that the most effective natural coastal protections—mangroves and coral reefs—are themselves restricted to the tropics and subtropics, the very regions where tropical cyclone storm surges pose the greatest threat? Mangroves cannot withstand frosts and therefore in their natural habitat only extend as far north along the Florida peninsula as Cape Canaveral. And yet in our shortsightedness humans have removed those very natural features, which could help protect us.

Paradise Lost?

Between 1943 and 1970 half a million acres of Florida mangroves were cleared to make way for smooth beaches—those beautiful and inviting stretches of pristine sand which have for decades attracted developers to build beachfront properties. Yet, paradoxically, that photogenic “nakedness” of sand and sea may be one of the things, which leaves those properties most exposed to the elements.

With the backing of The Nature Conservancy it seems mangroves are making a comeback. In Miami-Dade County they’re examining a planting program to protect a large water treatment facility. Of course biological systems can only reduce part of the flood risk. They can weaken the destructive storm surge but the water still gets inland. To manage this might require designing buildings with water-resistant walls and floors, or could involve a hybrid of grey (manmade) and green defenses. And if we can reduce the destructive wave action, that might allow us to build earth embankments protected with turf in place of expensive and ugly, but wave-resistant, concrete flood walls.

On March 28, 2015 The Nature Conservancy organized a conference and press briefing in Miami at which they announced their collaboration with RMS to measure the benefits of natural coastal defenses. The coastline of Miami-Dade, already experiencing the effects of rising high tide sea levels, presents real opportunities to test out ways of combatting hurricane hazards and stronger storms through biological systems. Our continued work with The Nature Conservancy is intended to develop metrics that are widely trusted and can eventually be adopted for setting flood insurance prices in the National Flood Insurance Program.

Coastal Flood: Rising Risk in New Orleans and Beyond

As we come up on the tenth anniversary of Hurricane Katrina, a lot of the focus is on New Orleans. But while New Orleans is far from being able to ignore its risk, it’s not the most vulnerable to coastal flood. RMS took a look at six coastal cities in the United States to evaluate how losses from storm surge are expected to change from the present day until 2100 and found that cities such as Miami, New York, and Tampa face greater risk of economic loss from storm surge.

To evaluate risk, we compared the likelihood of each city sustaining at least $15 billion in economic losses from storm surge – the amount of loss that would occur if the same area of Orleans Parish was flooded today as was flooded in 2005. What we found is that while New Orleans still faces significant risk, with a 1-in-440 chance of at least $15 billion in storm surge losses this year, the risk is 1-in-200 in New York, 1-in-125 in Miami, and 1-in-80 in Tampa.

Looking ahead to 2100, those chances increase dramatically. The chance of sustaining at least $15 billion in storm surge losses in 2100 rises to 1-in-315 in New Orleans, 1-in-45 in New York, and 1-in-30 in both Miami and Tampa.

Due to flood defences implemented since 2005, the risk in New Orleans is not as dramatic as you might think compared to other coastal cities evaluated. However, the Big Easy is faced with another problem in addition to rising sea levels – the city itself is sinking. In fact, it’s sinking faster than sea levels are rising, meaning flood heights are rising faster than any other city along the U.S. coast.

Our calculations regarding the risk in New Orleans were made on the assumption that flood defences are raised in step with water levels. If mitigation efforts aren’t made, the risk will be considerably higher.

And, there is considerable debate within the scientific community over changing hurricane frequency. As risk modelers, we take a measured, moderate approach, so we have not factored in potential changes in frequency into our calculations as there is not yet scientific consensus. However, some take the view that frequency is changing, which would also affect the expected future risk.

What’s clear is it’s important to understand changing risk as storm surge continues to contribute a larger part of hurricane losses.

Winter Storm Juno: Three Facts about “Snowmageddon 2015”

By Jeff Waters, meteorologist and senior analyst, business solutions

There were predictions that Winter Storm Juno—which many in the media and on social media dubbed “Snowmageddon 2015”—would be one of the worst blizzards to ever hit the East Coast. By last evening, grocery stores from New Jersey to Maine were stripped bare and residents were hunkered down in their homes.

Blizzard of 2015: Bus Snow Prep. Photo: Metropolitan Transportation Authority / Patrick Cashin

It turns out the blizzard—while a wallop—wasn’t nearly as bad as expected. The storm ended up tracking 50 to 75 miles further east, thus sparing many areas anticipating a bludgeoning and potentially reducing damages.

Here are highlights of what we’re seeing do far:

The snowstorm didn’t cripple Manhattan, but brought blizzard conditions to Long Island and more than two feet of snow in certain areas of New York, Connecticut, and Massachusetts.

The biggest wind gust thus far in the New York City forecast area has been 60 mph, which occurred just after 4:00 am ET this morning.

From The New York Times: “For some it was a pleasant break from routine, but for others it was a burden. Children stayed home from school, even in areas with hardly enough snow on the ground to build a snowman. Parents, too, were forced to take a day off.”

Slightly north, The Hartford Courant received reports from readers of as much as 27 inches of snow in several locations and as little as five inches in others. They asked readers to offer tallies of snow and posted the results in an interactive map.

Massachusetts was hit hardest, with heavy snow and a hurricane force wind gust reported in Nantucket.

The biggest wind gust overall has been 78 mph in Nantucket, MA, which is strong enough to be hurricane force.

From The Boston Globe: “By mid-morning, with the snow still coming down hard, the National Weather Service had fielded unofficial reports of 30 inches in Framingham, 28 inches in Littleton, and 27 inches in Tyngsborough. A number of other communities recorded snow depths greater than 2 feet, including Worcester, where the 25 inches recorded appeared likely to place it among the top 5 ever recorded there.”

There’s more snow to come, but the economic impact is likely to be less than anticipated.

Notable snowfall totals have been recorded across the East Coast. Many of these areas, particularly in coastal New England (including Boston), will see another 6-12 inches throughout the day today.

It’s too early to provide loss estimates, and damages are still likely as snow melts and flooding begins, particularly in hard hit areas of New England like Providence and Boston. However, with New York City spared, the impact is likely far less significant than initially anticipated.

RMS and Risky Business: Modeling Climate Change Risk

Earlier this year, RMS partnered with the Risky Business Initiative, a year-long effort co-chaired by former New York City Mayor Michael Bloomberg, former Treasury Secretary Henry Paulson, and Farallon Capital founder Tom Steyer to quantify and publicize the economic risks the United States faces from the impacts of a changing climate.

The report, which launched today, has been widely covered in publications ranging from Fortune and The Wall Street Journal to The Hill. It builds on the best available scientific evidence, including both the Intergovernmental Panel on Climate Change (IPCC) and National Climate Assessments, to highlight the risks and cost a changing climate will bring to the business and financial communities the report addresses.

The report details the impact of climate change at the county, state, and regional level; it is the highly vulnerable coastal regions exposed to rising sea levels and the potential for changes in storm activity where RMS has been privileged to contribute our expertise and modeling.

RMS North Atlantic hurricane and storm surge models are based on a base climatology defined by the historical record of storms and represents the current state of the climate. Sea-level rise will increase the risks associated with storm surges and a changed climate may lead to changes in the frequency and intensity of hurricanes the impact the U.S. East Coast and Gulf States.

To address the potential impacts of such changes, RMS pulled together a cross-functional team from our model development group and consulting teams to implement the changes in storm frequency and sea-level rise in our model and analyze the impacts against our database of U.S. property exposure. The team worked with leading climate and hurricane experts and the Risky Business team to understand the latest scientific thinking and gather the information needed to adjust our model from the peer review literature.

In the space of just a few months, the team developed nearly 20 versions of our storm surge hazard model to reflect the expected increase in sea-level rise through the coming decades up to the year 2100, as well as the range of uncertainty captured by the latest IPCC assessment. In addition, the team developed several hundred alternative scenarios of hurricane frequency to model how hurricane frequency may evolve with different “Representative Concentration Pathways” used by the IPCC to describe possible climate futures, possible depending on how much greenhouse gas is emitted in the years to come.

The results of RMS’ analysis, quantifying the changes in losses to hurricanes and storm surges through the coming century have been fed into the Risky Business econometric modeling to quantify the cost to the U.S. economy.

Our analysis highlights that the sea-level rise alone – one of the most certain aspects of a warmer climate – has the potential to more than double the economic losses to hurricanes and storm surges by the end of the century if left unchecked.

RMS, along with Risky Business, recognizes that the analysis is not definitive; however, the potential costs can be quantified and the risks of in-action assessed. This collaboration has developed an invaluable database of information on the impacts climate change on hurricane risk, and by extension, the U.S. economy as a whole.

Just as the Risky Business Initiative hopes to promote a non-partisan discussion on the risks of climate change within the business and financial communities as a whole, RMS hopes that this work and our continued collaboration with the scientific community will lead to continued dialogue in the (re)insurance and catastrophe loss modeling community on the impact of climate change to our business.

Visit http://riskybusiness.org/ to view the full report.