A bulkhead is a barrier wall, often made of engineered materials such as concrete, metal or composites and designed to stop beach or soil erosion. Unfortunately walls or bulkheads and trees do not always coexist well. Expanding root systems can encroach on bulkheads. Existing tree roots can be damaged when bulkheads are installed. Good solutions to problems between bulkheads and trees require careful consideration of construction and environmental factors, as well as adherence to local regulations.
Problems often crop up when homeowners fail to factor in the mature size of trees when planting them near bulkheads. For the first 10 or even 20 years of the tree's life, the roots do not disturb the wall. As the tree approaches mature size, major roots, which often extend outward from the trunk to at least the width of the canopy, come up against the wall or its footings. As the roots continue to increase in size and length, they may raise bulkhead sections or penetrate small cracks in the construction material. This may eventually threaten the bulkhead's integrity.
When planting young trees in the vicinity of a bulkhead, property owners should make sure to allow sufficient distance between trees and bulkhead. Tree canopy sizes vary widely, but in general, all trees should be at least 10 feet from the bulkhead and medium to large trees should be 20 to 30 feet from it. There are some exceptions to this rule. Palm trees, for example, grow tall, but do not have extensive root systems or wide canopies.
When new bulkhead walls are constructed, existing tree roots may block the intended path of the wall. Young trees can sometimes be transplanted elsewhere. Mature trees present different problems. Cutting through roots to create a trench for the bulkhead can destabilize trees, even if the roots are as small as 1 to 3 inches in diameter. Trees with severed roots are more liable to topple in storms. If mature tree roots are in the path of a new bulkhead, it is sometimes necessary to fell the tree and remove the roots.
If tree roots have damaged an existing bulkhead, consult local authorities before making repair or replacement plans. Changing perspectives on wave action and erosion control have made some traditional solid bulkhead types less desirable, and in some areas, authorities only permit them when other erosion control options are untenable. Bulkheads made of natural materials are sometimes the erosion controllers of choice. Living bulkheads, green belts of mixed vegetation, are also sometimes recommended for erosion control. These may include trees whose roots become an asset, holding soil and preventing erosion.
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