Citation | BC Conservation Foundation. 2012. Cowichan Lake Shoreline Habitat Assessment: Foreshore Inventory and Mapping Project, Volume 1 - report. Prepared for Fisheries and Oceans Canada. |
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Organization | DFO |
URL | http://www.cowichan-lake-stewards.ca/CSSP_Bkgnd/Cow_Lake_Report_Vol_1.pdf |
Abstract/Description or Keywords | Over the past decade Cowichan Lake has undergone significant growth of new "part time" summer residents, who are attracted by the area’s natural aesthetics and recreational potential. There is a growing demand for new recreational real estate (and amenities) that has prompted a dramatic increase in lakeshore residential development. Planning for future land development at Cowichan Lake is a complex challenge and balance between public demand for housing, economic realities of the region, and established social and cultural traditions of the affected communities. To ensure the planning process is well informed, a solid understanding of the lake’s aquatic riparian resources and values is essential. The Cowichan watershed supports anadromous (sea-run) and resident fish species/stocks, which in aggregate contribute to significant First Nations, commercial and sport fisheries (Westland, 2005). Cowichan Lake serves as a licenced water supply for the Catalyst pulp mill (in Crofton), and as a source of drinking water for residents of the Town of Lake Cowichan, Crofton and smaller lakeside communities. The watershed also provides critical habitats for many important wildlife species. For all of these reasons, local residents have expressed a strong desire to preserve and protect the watershed’s natural capital for future generations. The main objective of this report is to provide a baseline overview of the shoreline habitat attributes of Cowichan Lake. Methods employed are discussed in detail, and are now a standard being used to map other large lake shorelines throughout the Province. The mapping protocol should allow stakeholders to understand current shoreline conditions, and measure and monitor changes in the future. Some success is being reported in the Okanagan and the Kootenay regions, where a three step process has been adopted to help integrate environmental data with land use planning. The process involves the following steps: 1. Foreshore Inventory and Mapping (FIM) is a protocol being used to collect baseline biophysical data about current habitat conditions of a shoreline. The FIM uses a map-based approach to describe the shoreline. Data is compiled on shore types, substrates, land use and habitat modifications that are geo referenced and uploaded into a Geographic Information System (GIS). This information is then combined with fish population and other environmental inventories to enhance its interpretive value for land use planning decisions. 2. An Aquatic Habitat Index (AHI) is generated using FIM data to determine the relative/comparative habitat value of shoreline segments. This index follows similar methods that were developed for lakes in the BC Interior. The AHI integrates features such as substrate composition, shore spawning use, presence of aquatic vegetation and alike to estimate the habitat value of a particular shoreline segment. 3. Shoreline Management Guidelines are prepared to identify “Shoreline Vulnerability.” Shoreline vulnerability is based on the AHI (step 2 above) and is a risk-based approach to better protect ecologically sensitive shoreline features This report represents Step 1 in this three-tiered process. Data has been compiled from field surveys including assessment of biophysical conditions of Cowichan Lake’s shoreline (October 2010); fish abundance sampling at representative shoreline index sites in July 2011 and September 2011; assessment of unmapped inlet streams to determine potential fish use; assessment of important shoreline segments for reproduction of the SARA-listed Vancouver Lamprey (Lampetra macrostoma; Fundy Aqua Services 2011); and, Cowichan Lake Erosion Assessment by Kerr Wood Leidal Assoc. Ltd. (2011). These data have been linked to native fish species and their seasonal dependence on the lake’s shoreline ecosystems. Results provide valuable guidance to land and water use planners concerning critical features, habitats and related resources for the shorelines of Cowichan Lake. A brief summary of results include the following: Impacts to the shoreline were determined from categorical descriptions of the level/types of disturbance observed around the lake. It is estimated that 25% of the shoreline has a high level of impact (> 40% disturbance), which accounts for 25.3km of shoreline. Areas of low impact (less than 10% disturbance), or no impact, account for 55% (55km) of the shoreline. Impacts include lakebed substrate modification, riparian vegetation removal, retaining walls, docks, beach grooming and similar riparian incursions. In total, it is estimated that 29.4% or 29.5km of the shore length is disturbed while 70.5% or 70.6km remains in a natural state. The most dominant land use around the lake is forestry (48%), followed by single family developments (30.5%), and industrial/park lands (6%-7%). Disturbance was highest along shorelines where single family housing is the dominate use (64%). Wetlands and stream mouths are the most rare shore types, accounting for 0.5% and 4.6% of the total shore length, respectively. The most common shore type is gravel beach, dominating 72% of the lake's shoreline perimeter. Gravel shorelines also account for 92% of shoreline disturbances on the lake. Aquatic vegetation occurs along 21% of the shoreline and is important habitat for juvenile salmonids. Most (20%) of this vegetation was classed as emergent (hydrophilic shrubs such as Myrica Gale and willow spp.), while submergent vegetation was rare, and only abundant in the lake's outlet and some inlet stream mouths. The recent discovery of the aquatic invasive plant, Eurasian Water Milfoil, may change this scenario in future (should it become well-established). In an effort to relate the condition of shoreline riparian vegetation to adjacent land use, the FIM rated shoreline vegetation as either "patchy" or "continuous". Single family land use once again had the highest occurrence of impacted vegetation. The following summarizes Cowichan foreshore modifications observed: Docks were the most common structural modification observed, with a total of 596 counted. Both pile-supported and floating docks were observed. Often accompanying docks are floating log boom-stick structures designed to “dampen” the height of waves. These are becoming a common feature in association with docks, and are now found on 12.5% of the lake’s shoreline. Retaining walls were the second most common structural modification, with 360 observed. Many walls are constructed of cement, and are often associated with a modified beach. Walls occupy 9% of the shoreline, or 9km. |
Information Type | report |
Regional Watershed | Vancouver Island South |
Sub-watershed if known | Cowichan |
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Comments | |
Project status | complete |
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