| Abstract/Description or Keywords |
The Cariboo River, Cottonwood River and Horsefly River watersheds were identified in the Cariboo Chilcotin Land-use Plan (CCLUP) as priority watersheds where hydrologic stability should be a land and forest management consideration. To assist in the implementation of the CCLUP, an integration process was initiated and a Fisheries Target Risk Assessment (FTRA) was completed. The FTRA determined that the potential risks to fish habitat in the Cottonwood and Horsefly River watersheds were high, and in the Cariboo River watershed the risks were moderate. In response to the FTRA report and CCLUP requirements, the Cariboo Region Interagency Management Committee (IAMC) identified the need for an independent assessment of the three watersheds to inventory current physical conditions, define potential risks to fish resources, assess and interpret land use impacts that may affect fish resources, and interpret watershed conditions with regard to current forest development plans. In May 1997, a contract funded by Forest Renewal BC (FRBC) was issued to Dobson Engineering Ltd. and Chapman Geoscience Ltd. to complete an inventory of watershed conditions affecting risks to fish habitat in the Cariboo, Cottonwood and Horsefly watersheds. Background information on watershed characteristics and land-use concerns was assembled from Watershed Restoration Program reports, Department of Fisheries and Oceans reports, and other agency reports, and from interviews with stakeholders. Aerial overview, air photo and ground-based assessments were completed in the watersheds. A sample of roads and channels was assessed in each of the watersheds based on the results of the aerial overview. The following observations were common to all of the watersheds: 1. Where placer mining had occurred, stream channels have been disturbed resulting in increased sediment supply that overwhelmed the potential effects from other land use activities. Channel re-stabilization was observed and the Supply of coarse sediment was reduced at locations where mining had been abandoned. 2. Access roads to placer mining operations have been constructed to a low standard with inadequate drainage works. As a result, sediment is transported off the roads into adjacent streams. 3. Where private land has been developed for agricultural uses and the land has been cleared to the edge of streams, subsequent bank erosion and channel migration was common. The primary cause of the channel instability was the loss of stream bank integrity due to the removal of the stream side vegetation. A secondary factor was the effect of cattle disturbance along stream banks. 4. Erosion of road running surfaces and ditch lines was observed on all active forest roads inspected, as a result of the use of fine-textured native materials in the subgrade, and minimal use of sediment control structures both during and after construction. Where drainage and sediment control works were absent at stream crossings, sediment impacted the streams. |
