When an area floods repeatedly over the course of several growing seasons - even if it’s only to a depth of a couple of inches, affected trees may decline as their root systems gradually drown.
This situation occurs most frequently when construction projects alter the flow of runoff into previously well-drained areas.
The impact of this type of flooding is greatest when it occurs when trees are in full leaf, especially when temperatures are very warm in mid-summer. While still serious, trees are less severely impacted when flooding occurs when temperatures are cool/cold and trees are fully dormant, above right.