That's a very good question, but it could be a long answer. I'll try to be as short as possible.
I think the flood mapping that we have done with the Quebec government is really along rivers. It's much easier to do, and it's not around urban areas because, in urban areas, it's obvious that infrastructure like pavement, etc. is going to completely change the risk of flood. When doing it in rivers, the hydrological models try to handle the watershed and the way that the water streams around the watershed. We have done some studies to see the influence of modifying the watershed. Now, this usually has an impact on a much longer term. I think the 10-year rule is a good rule because, in that sense, you can also introduce modification to the watershed and to the surface to see if there's any influence.