Flood Damage to Forest Stands

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The flooding that has resulted from Hurricane Florence in much of North Carolina may have significant impact on forested land in the state. There are several factors to consider when assessing the impact of flooding on forest stands:

  1. Duration of flooding – the longer the tree roots are exposed to flooding, the higher the potential for injury. Most trees can tolerate 24-36 hours of flooding without longterm effects, except for pines, which will be less time.
  2. Species – Many of our bottomland hardwood stands are adapted to periodic flooding and will likely recover with no longterm effects. Pine stands that remain under water for serval days to weeks, may likely become stressed which will result in reduced growth next year and can lead to other pest problems later on.
  3. Age – Older trees and seedlings could have a higher potential for injury, especially seedlings. If seedlings are totally submerged in water for several days or have been buried in mud or uprooted will likely result in the death of the seedlings.
  4. Vigor – Vigorously growing, healthy trees can withstand flooding better than trees that have experienced stress over the growing season, such as drought or insect and disease issues.
  5. Season – Most of our trees are in the last stages of growth for the year and will likely have less effects from the flooding as opposed to flooding in the early spring. This should help trees to recover easier from the flooding event.
  6. Temperature and Oxygen – Cooler flood water is less injurious to trees than warm water because cooler water can hold more dissolved oxygen. Flowing water can also hold more oxygen than stagnate water.
  7. Brackish Water – In many of our coastal communities, brackish water pushed in from the sounds and ocean, can be the most damaging to forest trees. The concentration of salinity in these brackish waters along with amount and duration of exposure, will likely cause the most injury to forest stands along the coastal region.

The next 6-8 weeks will likely be the most critical time for many of our forests. Landowners should not be too quick to act when it comes to thinking about salvage operations. After the flood waters recede, newly planted stands should be the first to be evaluated to determine if the seedlings will survive. Mid-rotation stands will likely have the least impacts, and mature stands will need to evaluated after new planted stands. Always document damage and conditions of your forest with pictures as soon as it safe to get in and evaluate them.

Contact your local Extension Agent, consulting forester, or County Ranger to help you evaluate your forest stands and with help to determine the next steps in remediating damage caused by Hurricane Florence.

Reference:  Johnson, William M. “Floodwaters Can Affect Health of Landscape Trees, Plants.” Texas Agri-Life Extension. 2008.