Every year floods make their way through populated areas, costing lives and millions of dollars in damages, devastating communities, and grinding local economies to a halt. If you’ve ever experienced one yourself, you know how powerless it feels to be up against mother nature. And if you haven’t, be careful in thinking it can’t happen to you.
Nearly every major city across the world is susceptible to extreme rainfall and has areas that are vulnerable to flood risk. Luckily, we’ve developed strategies and structures over the years to reduce our vulnerability and mitigate our risk. We still can’t change how much it rains (at least in the short term), but we’ve found lots of ways to manage that water once it reaches the earth to limit the danger it poses to lives and property. Today, we’re talking about how large scale flood control structures work on rivers.
We all know generally what a flood is: too much water in one place at one time. But, I think there’s still uncertainty in how floods actually occur. Part of the reason for that confusion, I think, is the huge variety of scales we have when talking about flooding. Most river systems are dendritic. The topography of the land and the long-term geologic processes mean that streams join and concentrate the further you move downstream just like the branches of a tree. A watershed is the entire area of land where precipitation collects and drains into a common outlet; it’s a funnel. And as you move downstream, those funnels start to combine. The further you go, the larger the watershed becomes as more and more streams contribute to the drainage. So watersheds can be tiny or gigantic. More details
