Rebecca Wodder, president of American Rivers, wrote an interesting piece in this weeks PrairieFire on the rising costs of flood control, and what some communities are doing about it. I don't know where she got her numbers from, but even after spending $123 billion in inflation adjusted federal tax dollars over the last 50 years, the annual cost of flood damage continues to rise at 2.9% per year. That's a stunning set of numbers. Forget fish habitat! Here are real costs - and we don't know how fast they will continue to rise - or what the precise effects of future climate change will be. Why do people keep building on floodplains!
Unbounded uncertainty. Levees and other engineering structures work as long as the system doesn't exceed expectations - expectations that are based on the "period of record".