Yet amidst these brutalized landscapes are changes for the better. The thick, shady trees send down deep roots to anchor soil from eroding during normal spring floods. Young northern pike are abundant, the result of adult pike spawning in huge new flooded shallows. So are underwater insects, which have thrived on decayed leaves and other organic matter the receding rivers pulled in from the landscape. These are a few examples of how a flood can be good for a river ecosystem, says Richard Sparks, an aquatic biologist at the Illinois Natural History Survey.
Floods systematically replenish and reshape land, vegetation, fish, and wildlife.
At first, that would seem like it could only be destructive. But many ecosystems are actually maintained by disturbances. And if you don't have a disturbance, then your ecosystem changes into something else. That's true of prairies and prairie oak savannahs, and it's also true of the flood plain. Sparks extensively researched the outcomes from the famous Mississippi River flood of 1993, particularly around its epicenter in Alton, Illinois.