Disaster resilience? What a difference ±3% can make.

LOTRW’s September 20 post suggested that if “governments are instituted among men” to secure rights to life, liberty, and the pursuit of happiness on this violent planet of ours, then those governments ought to give some priority to building community disaster resilience.

George Leopold’s guest post cites one claim to just such action: Lyons, Colorado’s decision to invest in a $25,000 flood warning system may have saved a few hundred lives. Independently, another colleague has called attention to a story run by the Los Angeles Times: with previous tragedy in mind, Boulder, Colo., was ready for flood. According to the article, the price tag in this case was a bit higher: $45M in flood control projects since 1997. Here the presumed benefits to the city included saved property and reduction in business disruption as well as lives. (In both these instances, it is hard to estimate the actual savings, and thus the returns realized, on the investments. Chances are good both communities, in hindsight, wish they’d done more.)

These two community experiences provide a partial answer to a more general question: how might disaster resilience be accomplished, community-by-community, in practice? Certainly, it can’t be achieved by any single dramatic action, accomplished overnight. What’s required instead is a series of incremental measures, sustained over many years. Let’s take a closer look. The 1500 Lyons residents spent less than $20 each, total, on their protection. 300,000 Boulder residents invested an average $10 per person per year over a fifteen-year period (the actual figure might be even less; this assumes no outside help in the form of federal or state-level aid).

These weren’t large sums.

Now consider what happens in most towns and counties absent such measures. Let’s say, for the sake of illustration, not bothering to be too precise, that a town’s economy and property values grow by 3% a year, roughly following national trends, and that the town faces one or more natural hazard threats capable of shutting down the entire town every so often, say once in one hundred years. According to the (very approximate) rule of 72, the town’s risk exposure will double over each 24-year period (72 ÷ 3). Then, for example,
if that 100-year event occurs sometime in the interval 25-50 years out, the losses will be more than double those of today. If the event occurs a century from now, the loss will be 16 times as great. Of course this loss is in the distant future. Its present discounted value (PDV) is a greatly reduced figure. If this growth in exposure corresponds (again, simplistically) to prevailing interest rates, then the present discounted liability of an event 100 years out is comparable to today’s risk. (Note, however, that in this instance the present discounted risk summed over all future events extending through time is unbounded, infinite).

Now suppose that instead those same townspeople commit to a 3% reduction in risk each year. Then, applying the same rule of 72, the community risk would be halved every 24 years. The projected loss from an event occurring 100 years in the future would be 1/16th the cost of that event occurring today – and that’s before taking into account the present-discounted value of that distant future event. For such a community, the total future risk of hazards is bounded and small.

The Boulder and Lyons investments fall short of what’s required for a 3%-per-year reduction. And, as analysts have reminded us frequently in recent days, so-called 100-year events don’t simply occur once in a hundred years (in principle, they may average out to that over a 10,000 year period, but this is unlikely for myriad reasons). In addition, a town like Boulder or Lyons may face a 100-year flood problem, but many other risks (smaller floods, wildfires…) may occur more frequently; some very large events (1000-year floods, meteor strikes…) may occur less often but should still be included in any risk management strategy.

The figures above leave open any discussion of what measures are available and/or required, and what costs must be incurred, to reduce risk by 3%. To answer these questions requires community-by-community analysis. Communities could look at land use, building codes, new construction versus retrofits, for example. They could choose to retire structures built in floodplains or on seismically-active zones in favor of safer locations. They could call for incremental tightening of building codes over time. They could harden critical infrastructure and build in margin and backup to reduce single-point failures. Presumably communities would address the less expensive measures early on, and then take advantage of longer lead time to tackle the tougher, more expensive problems.

One of the least expensive measures, yet one promising great benefits over the longer term, is surely building public awareness about the local threats, their natural and social origins, and the engineering and policy measures available to manage those risks. Such education is cheap and at the same time builds the needed community buy-in for the tougher choices that lie ahead. It should be a strong choice for year 1.

Can such 3%-per-annum reductions be achieved in practice? The answer would seem to be a cautious yes. Commercial aviation provides a success story. Over the past fifty years, flights have increased something like tenfold, while accidents, though variable year-to-year, have remained roughly constant. This has been achieved by incremental advances in all aspects of meteorology, airframe design, manufacture and maintenance, airline and FAA procedures, and pilot and crew training that go into flight safety.

The United States could do worse than to make the NOAA/NWS Weather-Ready Nation initiative a point of departure for such a (much broader and comprehensive) community-level thrust.


This post may strike many as being a bit pointy-headed and obtuse, and others as being too simple-minded. Both accusations have merit.

The basic point is a simple one: Every community faces a choice between (1) allowing its vulnerability and risk to natural hazards to ratchet up a bit each year, and intermittently suffering disastrous consequences; or (2) reducing its vulnerability and risk by small amounts each year, and then (providing nature allows a bit of breathing room early on) discovering it’s able to take natural extremes in stride.

The implementation isn’t so simple. It requires far more rigor and exactitude. The starting point for every community ought to be some kind of self-assessment, some process of building community consensus with respect to disaster resilience, and development of a plan. The execution begins with commitment to sustained mitigation efforts, but requires disciplined, coordinated, sustained approaches to the engineering, regulatory, educational, and other dimensions of disaster reduction. That starts at the local level, but must be achieved in a statewide and national context.


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