Search

Handling boulders in the restoration work

  • The beginning of the B-section usually constitutes the defining sections that maintain the upstream water level. Make sure to raise the defining section as close to the original level as possible, which can be calculated when the watercourse is inventoried. This allows the upstream section can flood the floodplain to a greater extent, thereby also reducing the flow energy in the water. Sometimes, external materials such as gravel and rocks may need to be added to build up the defining section.
  • Anchoring boulders is an important step and is best done by the operator digging a hole in the bottom substrate before placing the boulders, or by usning grab bucket to lift the boulder and moving it back and forth to position it correctly. Finish by using the machine’s power and the lower part of the bucket to drive the rocks into the bottom.
  • Build structures using the most common boulder sizes from the material available. Save larger boulders to “decorate” the structures with.
  • Create variation in the height and width of the structures. This adds variation in both appearance and function.
  • Incorporate the surrounding terrain into the restoration. If the enclosure is low, it generally also means that there are low boulder structures in the watercourse.
  • Keep the boulders together. Try to build the structures with multiple boulders and in clusters rather than placing them one by one.
  • Try to create smooth transitions by tapering in and out the structures. For a boulder accumulation, this can be done by placing boulders further apart from the densest bloulder area in the structure you are building.
  • If there are erosion banks in the watercourse, it might be a good idea to direct part of the current toward them to facilitate the erosion process, which washes out gravel and stones into the water that, in turn, create important habitats for many species.
  • Uncover erosion banks to speed up the erosion process.
Illustration showing an excavator digging and anchoring smaller boulders into the bottom material.
The illustrations show how we gradually work with anchoring boulders. This image series demonstrates how we work with smaller boulders.
Illustration showing several images of an excavator digging in the bottom material to make space for a larger block to fit and be anchored. The blocks are larger than 1 meter in diameter and do not fully fit in the bucket.
This illustration shows how we need to work with blocks larger than 1 meter in diameter that do not fully fit in the bucket.
Excavator in the watercourse with large boulders.
The large boulder has been placed too shallowly, which both looks odd and reduces, among other things, the boulder’s damping function.
Watercourse with a lot of boulders and stones.
Well placed boulders, both in clusters and individually at different heights from the water surface. This creates natural variation and functionality in different water flows. The boulders are placed in a way that creates a smooth transition between a calm section and a more flowing section.
About cookies
Accessibility statement

Follow us

Facebook Instagram Youtube Icon-enter

GRIP on LIFE’s channels

Facebook Icon-enter

Rivers of LIFE’s channels