Sorry, but I must disagree with some of the opinions here.
First, for those who blame building standards or stupidity.
This is a component, specifically on a short time scale. But what if a volcanoe dormant for thousands of years suddenly erupts. Or there is an earthquake where there has not been one in human history. What about meteorites, or a river changing its course?
On what time scale do we try to ensure safety from natural disasters? How much is it reasonable to spend, and on what time scale? This is a cost/benefit analysis that is done by insurance agencies all the time.
Second, for those who think we cannot change the course of natural disasters.
We have been holding the course of the mississippi river for quite a long time now. It is the natural state for rivers to change their course periodically and the mississippi has wanted to do so for quite a while. This is one of the largest civil engeneering projects ever undertaken by mankind, and incidentally is a big reason why flood insurance is handled by the federal government.
We mittigate the effects of drought and flood with the use of dams, levees, floodways, and wells.
As far as the weather, we certainly can project enough energy into localized areas of the atmosphere to affect it. That we do not currently do so is the result of a cost/benefit analysis, though certainly more research would be needed to make the technology reliable. We do seed clouds and thus change the distribution of rainfall.
Much of global weather is controlled by a few parameters like (here in the US) the 'gulf stream' and the 'jet stream', there are also the various cycles like ENSO (El Niño/La Niña). These seem to be controlled by relatively small perturbations in oceanic temperature and/or atmospheric pressure systems.
Not that I think it is a good idea to screw with global weather patterns, but there is no a priori reason why we couldn't.