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How to manage flood damage to trees

Quick facts

  • Flood damage can affect tree growth and tree survival.
  • Tree flood damage can be caused by soil changes, physical damage, insects and diseases.
  • The potential for damage to trees from flooding depends on when and how flooding happens and tree characteristics.
  • Trees may need special care following a flood to minimize longer-term damage.

Flooding may cause direct damage to trees by changing soil conditions, interrupting normal oxygen and carbon dioxide exchange between trees and their environment, sedimentation and physical damage.

Flooding also can weaken trees, making them more susceptible to damage from insects and diseases. The likelihood of insect and disease damage depends upon the severity of the flood and tree health. A tree in weak condition before a flood can be further stressed by flooding.

Trees that are flood stressed exhibit a range of symptoms that may include:

  • Leaf chlorosis (yellowing), followed by leaf loss.
  • Reduced leaf size.
  • Early fall coloration and leaf drop.
  • Watersprouts or small shoots emerging from the main stem.
  • Crown dieback.
  • Large seed crops or no seed crops in years following a flood.

Symptoms may progress and ultimately kill a tree tree over a period of several years or they may lessen as the tree recovers. It is very difficult to link a flood to the cause of tree death years later.

Timing of flooding

Trees are more likely to be damaged by flooding during the growing season than by flooding during the dormant season. Trees are most susceptible to flood damage in late spring just after the first flush of growth. Tree species begin their spring flush at different times so the timing of a flood influences the species that are likely to be damaged.

If trees are flooded by heavy rain or snow melt in late winter or early spring when the trees and shrubs are not actively growing, and the water recedes before growth begins, flooding usually is not a problem. Most tree species can withstand one to four months of flooding during the dormant season.

When flooding occurs during the growing season, especially during warmer weather, one to two weeks of flooding can cause major, long-term damage to sensitive trees and shrubs, even death with some species. Some species can survive as long as three to five months in flooded situations.

Types of flood damage

A long-duration flood, especially during the growing season, may decrease height and diameter growth of tree species that are intolerant of flooding. But height and diameter growth may increase for flood tolerant species.

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Tree care after a flood

Trees that are healthy before a flood are more likely to survive flooding in good condition. Tree care after a flood depends on whether you are managing many acres of woodland or a few yard trees.

For professional assessment  and care of tree damage after flooding, hire a forester or arborist.

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Mel Baughman, retired professor of forest resources, College of Food, Agricultural and Natural Resource Sciences

Reviewed in 2019

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