Watch Your Dirt Fun Fact of the Week!!!
Boulder Clusters are one of the Best Management Practices used out in the field today!
Boulder clusters are simple, natural-looking features that add visual diversity and habitat to degraded, uniform reaches. Consequences of failure are generally slight.
What are Boulder Clusters?
Boulder Clusters are large rocks placed strategically in a stream either one itself or in groups to protect eroding banks and provide instream cover for the organisms of the river. Natural streams with beds coarser than gravel often feature large roughness elements like boulders that provide hiding cover and velocity shelters for fish and other aquatic organisms. If a constructed or modified channel lacks such features, adding boulder clusters may be an effective and simple way to improve aquatic habitat.
What are the benefits of using Boulder Clusters?
Boulder clusters provide hiding cover and velocity shelters for fish through the turbulence found in their wakes. They also provide stony substrate for attachment-type macroinvertebrates. If bed material is fine enough for scour to occur, boulders also develop stable pool habitat and physical diversity associated with a range of depths, velocities, and bed material sizes. Boulder clusters can make a relocated or reconstructed channel look more natural and add visual interest to an otherwise uniform view. If desirable, boulder clusters may be configured to trap woody debris and provide additional cover benefits. Boulder clusters provide fish rearing habitat, and areas for adult fish.
What type of "boulder" should be used?
The boulders should be found along the surrounding watershed - as raw as you can find them! Or if boulders are not available, imported boulders should resemble native materials. Irregular-shaped angular boulders of durable rock are preferred, although some installations have been done with gabions and other man-made materials. Gabions and similar devices are aesthetically inferior and eventually fail due to abrasion, corrosion or vandalism. Boulders may be placed using a large excavator with a thumb, or other heavy equipment.
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Thank for reading and see you next week
- The Dirt Time Team