So, did the people of Houston's past not also think like this? Were the stormwater reservoirs sold as half-measures when they were built? Were the pipes they laid and the retention areas they constructed simply a false front or did they really believe them adequate?

Did the people of New Orleans not do this? Were their dikes that failed not constructed in anticipation of the largest storm they felt reasonable?

What happened?

Without a sense of history and a proper sense of humility, we just assume that the people of the past were ignorant fools, that those in the intervening years were greedy and selfish, simply unwilling to do the proper things to ensure their own security. Somehow we are different in our enlightenment. Maybe at last society will heed our expert warnings.

I think a more difficult challenge — the real problem — goes beyond the engineering or planning and gets into human nature. It's very plausible to me that the dikes in New Orleans were built to handle the worst event anyone could remember, plus a little more. Then complacency set in. Not only were there always more urgent things to do than maintenance, but having *solved* the problem we no longer needed to worry about it. Go ahead and build there, we've got you covered. What's one more? And one more?

We've written here about the Oroville Dam and our seemingly-genetic predisposition to de-prioritize maintenance (see "A Dam Mess"). We've also written a number of times about risk compensation, how making things safer and more protected only prompts us to extend the risks we are willing to take (see "Texting in Your Risk Gap" and "More on Risk Compensation").

Much like traffic congestion is a complex problem that cannot be solved by building more lanes, neither can flooding be solved by simply constructing more elaborate, complicated and violent stormwater management and regulatory systems. To think otherwise leaves out the human element. It also puts more people at greater risk.

2. Flooding is not the whole problem that needs solving.

While I have a hard time understanding it, there might be some good reasons why someone chooses to buy a house in a floodplain. Perhaps they got a good deal, don't plan to stay there long, believe it won't happen to them. Lots of these decisions that look terrible in retrospect can be easily rationalized along the way.

What's more difficult to understand is how a bank can make a loan on such a house. How can you get a mortgage in a flood prone area without flood insurance?

Well, answer this one: Why does your pension fund own mortgage backed securities containing homes in flood zones without flood insurance?

Or how about this one: Why does the Federal Reserve swap U.S. Treasuries for mortgages when those treasuries are highly rated and secure but some of the mortgages are in flood prone areas without flood insurance?