Every community needs a weather-ready stress test.

The story is heartbreakingly familiar. Once again[1], weather and water have hammered Louisianans. Figures put the recent death toll at 11, and the number of families displaced from their homes at 40,000. The cause? Two feet of rain falling over the area in something like two days, with another 6 inches or so in the days since. The scale of the disaster, still unfolding, defies comprehension. For those who lost loved ones, grief has come in an instant. Their lives will never be the same, and they know it – all too well. Those who’ve lost home, possessions, and treasured keepsakes sense that any climb back to normalcy will be steep and long; their pain is only beginning. State and local officials struggle to formulate an area-wide recovery. The rest of us – living outside the region, merely reading the news accounts – experience what the social scientist Paul Slovic calls “numbing”. The statistics overwhelm singular but myriad stories, and this tragedy merges with and dissolves into others unfolding nationwide and across the globe: rampant terrorism, large displaced populations confined to tent encampments or on the move, deaths due to the Zika virus, and more.

Speaking of personal narratives, media coverage in Louisiana has brought to light many examples of individual courage and neighbor-helping-neighbor. It’s clear that emergency response has gone far beyond that accomplished by state and local agencies. On the ground, professional responders were aided significantly by often-anonymous volunteers who either worked alone or self-organized to save lives and property. We’ll undoubtedly learn of many more examples of such love, compassion and fortitude in the recovery that lies ahead. To the residents of Louisiana, good-on-you!

Coverage of and commentary on this Louisiana flood of 2016 continue to light up the Internet. One example: a few words from Mark Schleifstein, a Times-Picayune reporter who provided insightful coverage of Katrina in 2005, and in fact wrote extensively for his newspaper about the build-up of vulnerability across the region back in 2002, years prior to that event:

The Louisiana Flood of 2016 was triggered by a complicated, slow-moving low-pressure weather system that dumped as much as two feet of rain on parts of East Baton Rouge, Livingston and St. Helena parishes in 48 hours. The record two-day rainfall in those areas had a 0.1 percent chance of occurring in any year, the equivalent of a “1,000-year rain”, according to the Lower Mississippi River Forecast Center, based at the Slidell office of the National Weather Service.

In the two-day period ending Saturday at 7 a.m., several parishes saw rainfall amounts equaling a 1 percent chance of occurring in any year, a so-called 100-year event. They included parts of Tangipahoa, East Feliciana, Washington, Ascension, Lafayette, Iberville and St. Martin.

Surveying Louisiana’s experience of the past decade, it’s natural enough to think:

• Whew! Glad I don’t live in Louisiana; I’m safe.
• Climate change is really messing with our weather.

The first reaction is wrongheaded. A look at rainfall data suggests that rainfall totaled two feet over two days over perhaps 10,000 square miles of surface area. (Even accepting a problematic terminology/framing), this may indeed be a “thousand-year” event, but with United States land surface area approaching some 4 million square miles, such an extreme might be expected to hit somewhere over a comparably-sized area within the United States every couple of years or so.

(NOAA 24-hour rainfall records suggest something like that is indeed the case. A sampling: Alaska, 15 inches, 1986; Arizona, 11 inches, 1970; California, 26 inches, 1943; Florida, 23 inches, 1980; Georgia, 23 inches, 1994; Hawaii, 38 inches, 1956; Illinois 17 inches, 1996; Minnesota 15 inches, 2007; New York 13 inches, 2014; Texas, 42 inches, 1979; etc.

These are records, not exhaustive inventories of the precipitation extremes in each state. The time series go back only 100-200 years, versus 1000 years. They strictly adhere to 24-hour time periods. Thus for example, there’s no note of the 17 inches of rain over a period of a few days responsible for the Colorado floods of 2013. There’s no mention of the impact of lesser rains over smaller areas, such as the eight inches of rain dumped over portions of West Virginia in a few hours in June of this year, killing 26. But you get the idea: even in relatively arid parts of the country, wherever we live, we can reasonably to expect to endure as much as a foot of rainfall in a 24-hour period every so often, most likely in the span of a single lifetime.)

The second reaction merits reflection. Scientists detect early signs of this feature of climate change; those of us in the general population can all see it coming. Nevertheless, posed this way, the problem risks appearing simply too big. It is pervasive but vague. What’s more, any solutions lie in the hands of “others” – elected officials, and business leaders of the energy sector. This invites us to be passive and/or to content ourselves with feelings of anger and reflexive finger-pointing at those we hold accountable.

A third thought, along different lines, might prompt us to act – and act more effectively:

I wonder if my community could pass a weather-ready stress test.

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An extended sidebar: On an individual level, we are familiar with such notions. For example the Mayo Clinic defines an exercise stress test this way:

A stress test, also called an exercise stress test, gathers information about how your heart works during physical activity. Because exercise makes your heart pump harder and faster than usual, an exercise stress test can reveal problems within your heart that might not be noticeable otherwise. An exercise stress test usually involves walking on a treadmill or riding a stationary bike while your heart rhythm, blood pressure and breathing are monitored. Your doctor may recommend an exercise stress test if he or she suspects you have coronary artery disease or an irregular heart rhythm (arrhythmia). The test may also be used to guide your treatment if you’ve already been diagnosed with a heart condition.

In another arena: For the past quarter-century, but more pointedly since the financial-sector meltdown of 2008, governments have been subjecting their banking institutions to financial stress tests:

A stress test, in financial terminology, is an analysis or simulation designed to determine the ability of a given financial instrument or financial institution to deal with an economic crisis. Instead of doing financial projection on a “best estimate” basis, a company or its regulators may do stress testing where they look at how robust a financial instrument is in certain crashes, a form of scenario analysis. They may test the instrument under, for example, the following stresses:

• What happens if unemployment rate rises to xx% in a specific year?
• What happens if equity markets crash by more than x% this year?
• What happens if GDP falls by z% in a given year?
• What happens if interest rates go up by at least y%?
• What if half the instruments in the portfolio terminate their contracts in the fifth year?
• What happens if oil prices rise by 200%?

[A little history]:

A bank stress test is a simulation based on an examination of the balance sheet of that institution. Large international banks began using internal stress tests in the early 1990s. In 1996, the Basel Capital Accord was amended to require banks and investment firms to conduct stress tests to determine their ability to respond to market events. However, up until 2007, stress tests were typically performed only by the banks themselves, for internal self-assessment. Beginning in 2007, governmental regulatory bodies became interested in conducting their own stress tests to insure the effective operation of financial institutions. Since then, stress tests have been routinely performed by financial regulators in different countries or regions, to insure that the banks under their authority are engaging in practices likely to avoid negative outcomes. In India, legislation was enacted in 2007 requiring banks to undergo regular stress tests. In October 2012, U.S. regulators unveiled new rules expanding this practice by requiring the largest American banks to undergo stress tests twice per year, once internally and once conducted by the regulators. Starting in 2014 midsized firms (i.e., those with $10–50 billion in assets) are also being required to conduct Dodd-Frank Act Stress Testing. In 2012, federal regulators also began recommending portfolio stress testing as a sound risk management practice for community banks or institutions that were too small to fall under Dodd-Frank’s requirements. The Office of the Comptroller of the Currency (OCC) in an October 18, 2012, Bulletin recommends stress testing as means to identify and quantify loan portfolio risk. The FDIC made similar recommendations for community banks.

Since the initial Dodd-Frank Act Stress Testing began the Federal Reserve has found that post-stress capital has increased. Furthermore, the Federal Reserve has continued to advance their expectations and adopt more complex scenarios in bank stress testing.

Statistician and risk analyst Nassim Taleb has advocated a different approach to stress testing saying that stress tests based on arbitrary numbers can be gamed. A more effective test is to assess the fragility of a bank by applying one stress test and scaling it up, which provides an indicator of how sensitive a bank is to changes in economic conditions.

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How might that apply here? Let’s start by making that question specific.

What happens to my community if/when we experience a foot of rain over 24 hours?

Whose lives are most in danger? What homes and property will be lost? Who will need to evacuate? Where can they go? What critical infrastructure will fail? Are hospitals and schools safe? What are the risks of cascading failure (e.g., electrical grid failure triggering disruptions of communications, water supply, road transportation, etc.)? What major employers will be compromised? How many small businesses will shutter their doors? What will be the hit to the local economy? How long will recovery take?

To ask these questions is to discover that our communities have much in common with the banks early in their quarter-century of experience with such tests. We learn quickly that we know far too little about the risks we face, with regard to their nature, their severity, and their particulars.

We also discover what little we do know is unsettling.

Such humility makes for a healthy starting point. It combines with the sure knowledge that the futures of people we know and love – not faceless strangers – are at stake to spur action.

A few observations.

First, note from the history of financial stress tests that the sector gradually discovered volunteer testing tended to be to generous. (We ought to recognize this universal human tendency from exercise stress testing; as individuals we kid ourselves into thinking we’re in better physical shape than evidence will support.)

Second, notice that the central question from stress tests isn’t “how likely is it that my community (or my bank, or my body) will be subjected to a certain level of stress?” But rather, “how will my community perform under a given stress level?”

Third, note that the wide range (and rapidly growing number) aimed at building resilient communities tend to be a bit vague on the importance of estimating community performance in this way. Take for example, these elements required to obtain a storm-ready designation from the National Weather Service:

• Establish a 24-hour warning point and emergency operations center
• Have more than one way to receive severe weather warnings and forecasts and to alert the public
• Create a system that monitors weather conditions locally
• Promote the importance of public readiness through community seminars
• Develop a formal hazardous weather plan, which includes training severe weather spotters and holding emergency exercises.

Meeting each of the required elements is certainly meritorious, and in the event, will save lives. The NWS and their participating storm-ready communities should be congratulated for their progress to date. But there’s no reason for complacency here. A plan, however formal, focusing on emergency response and not extending to building codes, land use, ensuring continuity of critical infrastructure, and appropriately stress-tested, leaves much to be desired. We can work together to take such next steps.

Fourth and finally, take note of Nassim Taleb’s comment with respect to the financial sector: he points out that rather than focus on a single arbitrary threshold, we need to focus on (community) fragility as characterized by performance under stress over a range of levels, and in several respects. For example, the invitation is to ask: what happens to my community if/when we experience several inches of rain over a few hours? A foot of rain over 24 hours? Heavy rains of several-days duration? And then expanding to ask similar questions under the stress of drought, or extremes of heat and cold, feet of snow, high straight-line and tornadic winds, for example. It’s essential to consider a wide range of diverse scenarios.

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A closing comment. Taleb uses the word fragility. Some might prefer the term resilience, arguing that it’s more positive. True enough. But to accept, maybe even embrace fragility fosters the appropriate attitude of humility. As the lessons of Louisiana remind us, we all have a big job ahead.

[1] Other recent instances include but are not limited to Hurricane Katrina in 2005 and floods of 2011.