Best-laid plans

MOTHER NATURE’S DOUBLE-BARRELED blast on the Gulf Coast has provided a discomforting but valuable insight into the limits of human competence and the stubbornness of human nature.

When water from Lake Pontchartrain flooded New Orleans in the wake of Hurricane Katrina, it prompted people to ask angrily why so many people were trapped in the city, and why it took so long for the federal government to respond. Three weeks later, as Hurricane Rita approached the Texas coast, many feared the worst. With images of New Orleans’ desperation and devastation still fresh in their minds, officials called for an evacuation several days ahead of the storm.

So what happened? Millions of people heeded the call, turning the interstates heading west and north from the coast into parking lots. Gas stations for miles around ran dry. Highway medians and shoulders soon were littered with useless cars, their drivers waiting anxiously for emergency workers to come by with a refill. Meanwhile, would-be travelers at Houston’s George Bush International Airport faced delays of up to five hours when more than 100 security screeners went AWOL.

Although most residents were able to evacuate in spite of the logjams -- particularly those savvy enough to navigate alternate routes -- others turned back in frustration. Had there been less advance notice, the snarl would have been even more severe, and the results much worse.

The problem in Texas wasn’t a lack of disaster plans. It was the size and novelty of the challenge.

The U.S. transportation system wasn’t designed to support mass evacuations. In fact, most of our highways can’t handle even daily rush-hour traffic. Evacuation plans are designed with that in mind, but their success depends on many variables, including some that are hard to foresee. People don’t always do what planners expect, causing setbacks and delays that cascade like dominos.

The difficult evacuation of coastal Texas has some planners worried that too many Americans live in vulnerable places, particularly at a time when extraordinarily powerful storms are becoming more frequent. A study this month in Science magazine shows that the number of Category 4 or 5 storms has risen to an average of 18 a year worldwide since 1990, compared to an average of 11 in the 1970s. No matter what the cause, scientists say this trend is likely to be with us for years.

In the long term, Americans have to confront the questions of how to gird against the gathering winds, and whether to give more territory back to nature. More immediately, though, the experiences with Katrina and Rita have provided important lessons about how people respond to a call to evacuate, and officials should heed them. As communities across the country revisit their disaster plans, they should keep in mind the images not only of people stranded on rooftops but also of those stuck on the medians.