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After the Flood

In the wake of flooding along the Red and Minnesota Rivers this spring, we are already receiving calls related to tree health in affected areas. When dealing with flood damaged trees, patience and common sense must prevail. There are obvious situations where flood waters have had immediate impact on trees that may require action in the next several weeks:

  • Scouring = where water movement has removed most of the soil around the root system.
  • Sedimentation = where new material has covered the tree's root system deeper than normal.
  • Mechanical damage = where wounds to the bark or sapwood occurred from current, wave action or floating debris.

Remember the timing and duration of a flood affect species differently. Cottonwood, willow, black ash, pin oak and soft maple have evolved as flood plain trees and are less susceptible to damage than conifers and upland hardwoods. Most trees can withstand a month of water if it is during the dormant season; as this flood was. How fast the soils dry out and how temperatures fluctuate will affect tree vigor in June and July. Trees should be left for at least two full months after the water recedes to see how they respond.

An excellent reference is the USDA-US Forest Service publication, "Flooding and its effects on trees".