Following Hurricane Katrina and other severe hurricanes, the U.S. Army Corps of Engineers revised its regulations for manmade flood control levees on both public and private lands to require no vegetation larger than two inches in diameter be allowed to grow on these levees. The Corps’ theory is trees weaken the levees and will cause flooding to be worse.
While this project is being undertaken, the grass is trampled away by machinery, and other vegetation is being removed according to the Corps’ plan. This is turning areas of the levees in Elmira into mere mounds of dirt with deep channels eroded into the soil from rainwater and runoff. It seems this could represent a more significant threat to levees than would leaving the vegetation in place in the event of a substantial rainfall, as there has been in the Northeast recently.
A city of Elmira employee stated that if the trees are not removed, the Corps will decertify the levee system. No one local, including the New York State Department of Environmental Conservation, is happy about this expensive, landscape-altering mandate. If the trees are not removed, the state could lose federal funds to repair levees damaged during floods.
This makes it sound like the Corps decided what it wanted to do and ensured that no one would be able to oppose it by tying compliance to funding. This is an untenable situation for state and local governments – forced to comply even if they disagree.
Even in the midst of the tree removal project, the animals that inhabit this area are clinging to their habitat. On June 27, while half of the trees have been removed already, my father and I were able to watch and photograph a juvenile bald eagle, which was almost directly across from us as we stood on the levee. Animals, which typically avoid human contact or habitats that are significantly disturbed by human activity, are still actively using this area, demonstrating its importance.
This change in regulation threatens not only local landscapes and environments but is also a national concern. Trees and shrubs are scheduled to be removed from 1,600 miles of levees in California. Taking that figure and applying it nationally amounts to a substantial change in the environment of our entire country.
Does this practice seem in keeping with the character of an agency whose website states, “Floodplains are complex natural systems that provide habitat for plants, fish and wildlife, and contribute to the overall health of the environment. Significant changes to floodplains can upset this delicate balance”?
In an effort to have this process at least delayed until further studies could be conducted, I contacted as many different agencies as I could think of — conservation agencies, state and local government agencies and officials and nonprofit agencies – seeking support or resources; however, I was unable to gain support from any of these sources. Each had reasons why it could not get involved or could not resist the requirements
This policy is a huge overreaction to one situation that was generally caused by the Corps’ own ineptitude as documented in a report that studied the flood caused by Hurricane Katrina. Trees were not the underlying cause of the problem. The levees were built with improper materials that were already allowing for water seepage to occur.
England has also had to deal with flood control problems in which trees were washed into cities, causing damage. Specialists in trees, floods and the environment worked together in looking at different options for managing trees. The plan includes coppicing riverside trees to stabilize growth and felling, collecting views on tree management from landowners and the local community, and choosing the appropriate method to balance flood risk with the environment.
Reasons given by the NYSDEC for the cutting of trees include the following: 1. To allow proper inspection, surveillance, and monitoring; 2. To allow access for normal and emergency operations and maintenance activities; 3. To prevent root-related damage to structures; 4. To limit those habitat characteristics that encourage the creation of animal burrows; 5. To allow full design-discharge capability of waterways; and 6. The presence of large trees near levee systems often precludes the growth of a healthy sod cover (due to light deprivation, etc).
A representative of the U.S. Fish and Wildlife Service stated his agency has always taken the position that vegetation on levees is neutral or beneficial to levee integrity based on the most recent science. This must, however, be determined on a case-by-case basis. In Washington State there have been exemptions to the tree removal policy. However, the Fish and Wildlife Service does not have any regulatory authority when it comes to levees – only the Department of Defense does.
Different agencies within our own government disagree on how best to manage this situation. If there is such disagreement over what should be happening, it would make sense to conduct further testing and studies to ensure that the correct path is being taken, considering the irreversible environmental changes this project will cause.
In 2007 the Corps was confronted with substantial evidence that trees do not threaten levees. In fact, the Corps had worked for decades to plant more trees on levees. One paper had been written by a Michigan University professor based on a report substantiated by the Corps. An engineer at the U.S. Department of Agriculture studied levees and concluded tree roots increase the sheer strength of levees. Computer models were presented to show tree roots provide more protection than a uniform grass covering. It was also stated that removing trees could create better conditions for burrowing rodents, which prefer open landscapes, and cause an increase in their population. An engineering chief at the Corps said studies were not integrated into their plans because the science was not relevant.
The Corps conducted its own study of tree roots along levees which concluded that tests are needed to determine the actual risks roots represent to levees. It also stated that plant roots reinforce levee soils and significantly increase sheer strength. Grass is the best on the surface, but shrubs and trees with deeper roots reinforce sheer strength of deeper soil, preventing deeper-seated failures. Another important question that could not be addressed in this study is how far a tree must be from the levee toe to avoid a tree falling in high winds and the root ball destroying the base of the levee.
Studies suggest that re-planting and creating new forests could diminish flood risk. Perhaps the solution to the flood management problem is not cutting down millions of trees but planting millions of trees – not destroying wildlife habitat but restoring it.
It is simply unfathomable that a government agency would continue on a destructive path, obliterating countless miles of viable habitat when there appears to be no substantiated evidence to support its reasoning to make these changes. The current science shows trees to be vital to levee systems. Studies the Corps itself has conducted do not support its plan. Scientific reports, based on its own studies, refute its claims of trees’ negative impact on levees. The Corps seems determined to ignore the evidence mounting against their plan and forge ahead.
If trees present a risk of being washed out or being blown over, causing catastrophic failure of the levees, it would take a substantial force to do this. Studies specific to the species of trees, and their size and age should be conducted to determine how much wind and/or water force it takes to wash out or blow down these trees. Then, it could be determined if these forces occur in the geographical region in question, and high-risk trees could be removed while trees not at risk could be saved.
by Kyle Reynolds
Kyle is a photographer with a passion for nature and wildlife. It is his hope to increase the public’s ability to enjoy and appreciate the natural world through his photography.