Sediment Control using Various Types of Sediment Traps

BUSK CREEK LANDSLIDE PROJECT

Location: West Arm Demonstration Forest, Nelson, British Columbia

Client: Kootenay Lake Forest District

Objective: To re-establish drainage patterns on the roads affected by the slide and to stop sediment delivery to Busk Creek. To distribute run-off drainage to avoid further surface erosion and degradation of the site and to re-establish native vegetation.

During ‘breakup’ of 1997, a debris avalanche swept across the Busk Creek forestry road, divided it into two channels, crossed the main Kokanee Park access road and ran into Busk Creek, a tributary to the Kokanee Creek spanning channel. The distance from top to bottom was about 640 meters. The estimated area affected by the event was 0.8 ha.

A significant quantity of unconsolidated material entered Busk Creek, including soil materials, rocks and gravel, and organic debris, creating a major sediment source in the Kokanee Creek watershed. In early summer of 1998, mudflow deposits again obstructed the park road. In November 1998, an assessment of the site and preliminary remediation plan was developed by William H. Wells, P. Ag. Consulting and Alan Davidson, P. Ag. Earth Science Specialist of Kootenay Lake Forest District in collaboration with Terra Erosion Control Ltd.

Terra Erosion Control Ltd. carried out this erosion control work in November 1999. The prescription included three types of treatments in order to compare their effectiveness:

1) conventional soil bioengineering structures, 2) sediment traps using dead materials (logs, rocks, re-bar, geotextiles, and straw bales), and 3) a combination of both, where live willow cuttings were incorporated with soil and straw flakes within the sediment traps.

Drainage improvement and structural reconstruction work was completed upslope of the slide’s initiation point, therefore significantly reducing further failures.

Follow- up assessments began early in 1999 to monitor the effectiveness of the treatment and to identify the necessary repairs and maintenance. Fill-in erosion control seeding was later undertaken.

Optimally, reviews and monitoring of the entire project are undertaken annually. This road and its effect on the hydrology of this landscape unit have a close relationship to the stability of the slopes and the successful rehabilitation of the landslide.