WX BRIEF

Droughts and floods

Too much-or too little-rain can have a huge impact on aviation.

By Karsten Shein
Comm-Inst, Climate Scientist


Aircraft take refuge on the only bit of dry ground at CLS (Chehalis WA) during the Dec 2007 flood of the Chehalis River. Flooding can have a direct and immediate impact on aviation, although normally the effects are more indirect.

Every now and then it's worthwhile for professional pilots to think about weather-related topics that may not have much in the way of a readily apparent connection to day-to-day flight operations.

We must remember that, while some atmospheric phenomena might not immediately impact your flying, they may affect your operational costs down the line, and even propagate into costs to a company that might ultimately require cutting back on their flight department expenses.

In short, a pilot should know as much about the effects of weather on their job as possible. Being able to discuss these topics with your boss may be what keeps you in your employer's cockpit.

Floods and droughts are just 2 examples of atmospheric events which, on the surface, don't really apply to a run-of-the-mill weather briefing-unless there's a Notam that your proposed destination runway is under water-but these events do have a significant impact on aviation.

Lately there has been an abundance of news coverage of widespread floods and droughts across the US. The flooding in the Midwest in June will likely be among the most expensive floods the region has ever seen.

Meanwhile, persistent drought across the southeast and southwestern US has many communities taking drastic water conservation measures. Similarly damaging floods and droughts are familiar to most parts of the flying world.

Australia has been under a persistent drought for a number of years, while parts of Europe have recently endured heavy floods. Much of Asia's southern and eastern coast is prone to massive flooding from typhoons that strike Indochina with alarming frequency.

Planning for averages

Droughts and floods are an unfortunate side effect of a region getting too little rain or more than it can handle, respectively. But what does that have to do with aviation? Quite a lot, actually. Like nature, the society of which we are part is largely the result of adaptation to average conditions.

Mays Island in Cedar Rapids IA during the flood of 2008, as seen from I-380 on Jun 12. The water covers all road bridges in the downtown area except for I-380, and completely covers Mays Island and most of downtown.

People thrive where conditions are relatively comfortable most of the time. Many of the world's major cities are built along coasts or in flood plains where a river has created fertile soil, and sufficient rainfall allowed crops to grow with abundance.

While the farmland has long been supplanted by skyscrapers and urban sprawl, these city's airports are there too. Most are located along the water's edge, in places that are very prone to flooding. Unfortunately, also like nature, we are shaped significantly by the impacts of extreme events, primarily because those impacts are devastating to the average conditions we have built around.

Even if we live in places where extreme events occur with some frequency, most of our infrastructure is not designed around extremes. Although some factors, such as crop damage, are difficult to proof against extreme weather (although drought-resistant crops are available), it is not an oversight that we don't adapt to withstand extreme forms of many conditions that we could.

In some cases, it is a matter of aesthetics or convenience. We don't want to live in cinderblock bunkers in Miami, nor in stilted communities in Iowa. In other cases, it's the tradeoff between the real costs of taking those extremes into account and the probability of costs that would arise if an extreme were to occur.

Imagine, if you will, the cost of adding another 10 ft of elevation to Runway 4L (elevation 12 ft msl) at JFK (John F Kennedy, New York NY) to reduce the risk of a hurricane storm surge that might inundate the runway once in the next few hundred years.

Networking

However, for aviation we need to consider something arguably more important to operations. We also rely extensively on highly interconnected and complex transportation, energy and communications networks.

Rainfall totals across the Midwest in early Jun 2008. Heavy and persistent rain generated widespread flooding that cut major transportation routes and destroyed most crops in the region.

All these networks have been built piece by piece as need arose, and all rely on each other to work effectively. While we like to think of things such as a concrete runway as being fairly robust, it is not the runway that will bring us to a standstill, unless it happens to be under water or has buckled in the summer heat of a drought-stricken region.

More likely, it will be that the roads bringing the fuel trucks to the airport are under water, or more likely, that you, your passengers or your cargo cannot make it through the floodwaters to the airport to get anywhere.

And while most larger airports will have redundant systems to provide emergency electricity to critical systems, a widespread power outage due to flooded substations may put a damper on getting flightplans into the FAA networks or paying for your fuel with a credit card that would have to be swiped through an electronic reader at the FBO.

In addition to paying an arm and a leg for fuel, we tend to figure that things like catered meals will go up as well, as the cost of food is rising in tandem with the costs of trucking that food from field to fork.

But if a drought or flood happens to hit a major agricultural region during the growing season-even if it's half a world away from your home base-you can bet that that croissant platter you've ordered for the VIPs is going to do some eating of its own-out of your flight department budget.

Definitive definitions

So, now that you've initiated the conversation with your boss, the inevitable questions will start to flow. What caused the flood or the drought? In an absolute world, you could simply say "too much or too little rain." But extremes of precipitation are only part of the equation.

For example, many times it is rainfall that has occurred miles away that winds up causing the floodwaters that sweep through a town. In places where monsoon rainfall is an annual event, heavy and nearly continuous thunderstorms can dump dozens of inches of rain on relatively flat terrain.

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