Almost everyone has seen the aftereffects of floodwaters, but not all of us have had the experience of watching the first flush of water flowing into a dry wash or riverbed. This video shows some dramatic examples. (Scroll ahead to about the 1:35 mark to see footage of the water itself.)
What shows up particularly well in the video is the debris the flow pushes in front of it—including, even in this desert environment, plentiful tree branches. It’s easy to imagine the greater debris the water might carry along with it after a wildfire in the mountains upstream: branches, ash, and even more sediment. These can easily block waterways (and, in built areas, storm drains), causing the water to flow in unexpected directions. The upcoming September/October issue of Erosion Control will include an article on dealing with the flooding and sedimentation problems in areas affected by fires.