Constant floods are one of the effects of global warming. Overpopulation leads to further destructions of our natural environment. Floods can destroy cities, agriculture and many industries that are important in the economy. Once the basic necessities such as food and water are affected, it will turn into a total disaster. And investors will become hesitant to invest in such cities and places that are dangerous to their businesses.
I think global warming is different. It's already on its name "warming" which means the earth is heating up. This can in fact lessen the floods around while it was the climate change is the one that can cause a flood.
There is no problem with the population as long as people are well disciplined and won't do things which can cause a harm to our environment. Floods can be fatal and not only those items that you have you listed can be destroyed by a flood but it can also end the lives of the many. I think that is more devastating because lives can not be returned anymore once it lost while those cities and agriculture can always be rebuilt again.