Over the long-run, tree vigor and structural stability will remain a concern. Pest problems, because of the massive number of stressed trees in the area will reach peak populations quickly and present a management problem for as many as five years into the future. Flooded soil conditions can quickly turn healthy trees into declining, pest-attacked trees. If the tree was healthy and structurally sound before the flood and resulting oxygen shortage, it has a good chance at recovery over the next few years. One aspect of flood damage, especially after flash or scouring flood conditions, is the toppling of trees.
Trees stand erect against most wind and flood conditions.
In air, trees tend to sway back and forth as they are loaded and unloaded. The period of the sway is set by mechanical properties of the tree and soil. Swaying can loosen tree roots from wet soil and lead to toppling under light winds. When a tree is partially under water in a moving flow, there is more constant pressure on the tree and less swaying. See Figure 1 .