Alot of people don't think of those thing when they're buying a home. Not once have I ever heard anyone say gee, I wonder why a house this close to that nice calm river is so cheap?
People and realtors don't do due diligence.
Most people look at a house like it, buy it and then like you say complain when a disaster befalls them. Anyone living in the 9th ward in New Orleans can attest to the fact that you probably shouldn't buy a home below sea level no matter how safe the gov't tells you it is.

Unfortunately it's up to the Gov't to stop the practice of allowing developers to build homes in unsafe locations, like on the downward slope of the North Shore mountains, the mouth of the Fraser River or on an earthquake fault like Victoria. But, given municipal gov't love of tax dollars I seriously doubt that things will ever change and people will continue to lose their homes and lives to unscrupulous bureaucrats, councils, politicians and developers.