Let’s try to summarize what we’ve covered in the textbook and module. Based on the risk factors, stream flooding can be caused by several situations:
- Too much rain falls on a drainage basin. Some rainstorms can stall out over an area, and continue dumping enormous amounts of water onto a local drainage basin.
- A downstream path is blocked. Many neighborhood floods are caused by a blocked drainage ditch or debris blocking up behind a bridge over a stream.
- Reduction in infiltration. Changes to the landscape can increase impervious surfaces which prevent water from being absorbed into the ground.
- Urbanization/Deforestation. Turning forest into farmland, or farmland/forest into suburbs increases runoff by causing water to move faster across a landscape. Slower moving water has more time to seep into the ground, and is especially important if you have low hydraulic conductivity soils like clay.
- Dam failure. Though rare, these failures cause massive floods with little to no warning. Indiana approves dam construction according to set guidelines, but does not inspect dams once installed.
This medical office was recently built next to Little Buck Creek at U.S. 31 and Banta Ave. on the south side of Indianapolis. It was later damaged by flash flooding: the creek sits behind the trees. Again, development pressures caused a building to be built on a poor location. (Photo: C. Thomas.)Please watch the video on the page, linked below. The video will cover watersheds, the hydrologic cycle, and how to understand flooding in terms of a system approach and flood risk in the context of the stream continuum.