Part of the problem now is that there are billions of us humans.　Ascivilization evolved, we moved to where we could live comfortably and wherewe had the resources to meet our needs for food, water, energy, shelter, andtransportation. We settled along coastlines and rivers where water was available,crops would grow, the climate was hospitable, and we could trade goods withother groups of people. We settled near volcanoes where the soil was fertile forcrops. As time went on, we concentrated in groups for defensive reasons; townsgrew larger but essentially in the same locations that were most suitable for ourbasic needs.
　　As our cities grew, our infrastructure became entrenched. Our shelters, ourtransportation systems, and our communication networks became permanent——houses, stores, factories, roads, bridges, dams, water supply systems, and powerlines. When natural events impacted us, we fought back. We built levees to holdback rising rivers,　not realizing that with our towns built on floodplains,　wewere living in the natural high-water paths of many rivers. We should not havebuilt in these places to begin with, but back then we did not know any better.We should have built our towns on higher terraces above the level of floods. Wecould have still used floodplains to grow crops but abandon them temporarilywhenever the water rose. Unfortunately, that is all in hindsight. Our towns grewup where they did, and we have to live with the consequences.