| Abstract/Description or Keywords |
Horsefly Lake (Watershed code: 160-635400-14100) has a surface area of approximately 5868 hectares and flows into the Little Horsefly River, which is tributary to the Horsefly River (BC MOE, 2011). Horsefly Lake provides habitat for a diversity of fish species, including sockeye, rainbow trout and kokanee and is a component of the Horsefly River watershed, which supports a prolific sockeye salmon stock and rainbow trout fishery, as well as providing habitat for Interior Fraser coho, Chinook, kokanee, and bull trout, making these waterbodies a key area of interest for resource managers and public stakeholders (Habitat Wizard; Lawrence, 2004; Holmes, 2009; Sebastian et al, 2003). While residential development is not widespread along the foreshore of Horsefly Lake, landuses such as forestry, mining, agriculture and recreation are present in the watershed and an integrated resource management approach is necessary to ensure sustainable natural resource management. Currently, lake management projects in the province of BC adhere to the following three-step process: 1. Foreshore Inventory and Mapping (FIM) – FIM is a broad scale inventory process that attempts to define and describe the shoreline of our large and small lake systems. 2. Aquatic Habitat Index or Ecological Sensitivity Index (AHI) – The AHI utilizes data collected during the FIM, field reviews, and other data sources (e.g., Land and Data Warehouse, previously published works, etc.) to develop and rank the sensitivity of the shoreline using an index. 3. Development of Shoreline Management Guidance Documents - Guidance documents are the final step in the process. By implementing this work, in conjunction with existing lake and watershed information, into a guidance document, it will facilitate informed decision making and prioritization of management issues and key areas of concern. This report presents Step 1 and Step 2 for Horsefly Lake. Foreshore Inventory and Mapping results (FIM) for this project provides valuable information regarding features, habitats, and other information for the shoreline of Horsefly Lake. A summary of the data collected indicates the following: • The total length of disturbed shoreline was around 7 km, while the remaining 111 km, or 94%, was described as being natural. • Natural area was the primary landuse, representing 83% of the shore length, with anthropogenic impacts over less than 2%. Rural land use was the next most common, accounting for nearly 9% of the shore length. Approximately 89% of the rural land parcels remain in a relatively natural state. However, these large, privately-owned parcels represent areas of potential future build-out, as development pressures increase, including subdivision and subsequent anthropogenic impacts. • The most predominant shore type observed around Horsefly Lake was gravel beach, which accounted for 52% or 61 km. Stream mouths accounted for 4.6 km, or 4%, of the total shore length, with stream mouth areas described as 6% disturbed. • Docks were the most commonly observed type of shoreline modification, occurring within both rural and single family residential areas. There were a total of 172 docks counted during the assessment, which equates to 1.5 docks per km. • The Horsefly Lake shoreline was recorded as having no impact along over 52% of its length. Approximately 42 km, or 35%, of the shoreline was described as having low impact, at less than 10%. Areas of moderate (10-40%) impacts accounted for 10 km of shoreline, or nearly 9%. Approximately 4% (4.4 km) of Horsefly Lake exhibited high levels of impact where greater than 40% of the shoreline was impacted. • Areas of high juvenile rearing value occur along 59 km and these areas have been disturbed along 3% or 1.8 km. Areas of moderate rearing value occur along 56 km of shoreline and are over 9% disturbed. Areas of low rearing value occur along 2.7 km of shoreline and were recorded as being 100% natural. The Aquatic Habitat Index (AHI) for Horsefly Lake provides valuable information regarding the estimated habitat values of different shoreline areas. The AHI is a categorical scale of relative habitat value that ranks shoreline segments from Very High to Very Low (Very High, High, Moderate, Low, and Very Low). The following summarizes the results of the AHI analysis: • Approximately 55% of the shoreline is ranked as Very High and High. Around 39% of the shoreline length is moderate, and the remaining 6% is ranked Low and Very Low. Only 3% of the shoreline length received a ranking of Very Low. • Areas of High and Very High habitat value were typically in association with stream confluences, wetlands and expansive natural areas associated with gravel and rocky shorelines. Most of the lower value sites were located in areas impacted by development, or where cliff/bluff habitat and associated bedrock substrates, rocky shoreline and narrow littoral zone occurred. • Within areas ranked as Very High, the shoreline was 95.8% natural. In High value areas, the shoreline was 94.5% natural and within Moderate Value areas the shoreline was 95.9% natural. Areas of Low Value were around 65.7% natural, while areas with Very Low value were documented to be 84.4% natural. The inventories and analysis completed as part of this study should help effectively manage and protect important aquatic resources along Horsefly Lake. The entire shoreline has been inventoried (FIM) and the relative sensitivity (AHI) has been determined. Horsefly Lake has areas of importance for salmonid habitat which have experienced anthropogenic impacts, particularly near the Little Horsefly River confluence. However, 94% of the shoreline remains in a relatively natural condition and 55% of the shore length surveyed received an AHI ranking of high or very high value. Information collected with the FIM and AHI steps should be integrated with existing initiatives, such as watershed-based fish-sustainability planning. Recommendations have been presented that are intended to aid foreshore protection, guide future data management, and for future biophysical inventory works. |
