Bowen Island shorelines may be classified as moderately to semi-protected from wave action based on fetch. The waves produced on Gulf Island shorelines from conventional ferries produce beach wash ups of several meters and are comparable in force to moderate waves along the exposed open coast (personal observation). The wash produced by the new catamaran fast ferries is up to nine times more powerful than those on conventional ferries according to a technical report by the BC Ferries Vice President of corporate safety and standards and the director of B.C. Ferries Deas Dock Maintenance facility (per the Times Colonist, Feb. 3, 1999 p.1).
Natural wave exposure is a major factor in determining the types of animals, plants and seaweeds along rocky shores. A change from relatively low to high wave exposure due to fast ferry wakes could have significant affects on the shore biota.
The present study was designed to assess the composition and abundance of intertidal animals and seaweeds at key points along the Bowen Island shoreline; and to provide the data as a baseline for comparison with any future assessments at the same precise locations. The results were evaluated in terms of potential impacts from waves generated by Pacificat catamarans.
For this study I established three permanent transects at key points along the Bowen Island shoreline. Two of these (KML Stations 113/99 & 114/99 are in areas of potential impact from fast ferry wakes while the third control site (KML 111/99) is outside the influence of such wakes. The attached map [50KB] shows the location of these stations.
Quadrats or squares were placed at 0.5m intertidal height intervals from high tide to low tide. The percent cover or abundance of animals and seaweeds was determined in each quadrat. On soft sediment the sand was passed through a strainer and the remaining animals were enumerated. On hard substrate the under rock biota was also assessed where possible. Each quadrat was also photographed. The detailed methods are given
in the following section. These details are included in order to allow other interested persons to set up similar transects. These same methods have been used in surveys in Burrard Inlet, the Gulf Islands, the east coast of Vancouver Island and Barkley Sound.
The study took place on August 9, 10 and 11, 1999. This was approximately 6 weeks after the start of regular sailings of the Pacificat catamaran.