An additional point on flooding to try to be cognizant of is that of man-made factors that can cause flooding where there hadn’t been any previously. This is much harder to get your arms around. Part of what causes the flooding problem where I grew up is that in the pre-EPA/environmental law days, the river floodplain was being filled in for suburban development. Now the same amount of water didn’t have its traditional holding area and had to find new places to go. Where my Dad worked, part of the problem was that the mountain ridge had high priced subdivisions go up one side and down the other and the ability of the ground to absorb water and slow runoff was greatly diminished to the detriment of those down below. Where my last home was it was easy to see how the building of the interstate highway created new barriers to flood waters, making it better in some places by blocking water, and conversely worse in others that retained the water. Also in the pre-EPA/environmental law days, large development didn’t include retention ponds to ensure runoff equilibrium pre and post development. If you live in areas where large scale development doesn’t have retention ponds, folks downstream will experience worse flooding than occurred historically under the same conditions. This is due to more runoff in shorter periods of time. You are not going to see this stuff on topographic maps but comparing topo maps with Google Earth shots might help you understand what has been done upstream that might impact you.