Conservation Priorities in the Squamish River Estuary To: Squamish Estuary Conservation Society

3.0 Management Guidelines

Based on the important conservation considerations outlined in Section 5. 0, the local data, and existing literature on wetland ecology, the Squamish Estuary is mostly likely to remain a healthy ecosystem if: (1) fresh and marine water quality is maintained for the ultimate sustainability of plant communities and their consumers - everything from benthic invertebrates to fish; (2) bird staging areas are protected from direct disturbances; (3) human recreational activities in key wildlife breeding areas (sites with high levels of structural diversity) are properly managed; and (4) linkage to the contributing watershed is retained and increased.

The Squamish Estuary would best be managed by adopting a land use gradient model that takes into consideration both wildlife requirements and the economic needs of the town.

The gradient would range from wildlife use only in the pristine western portion of the estuary (West Delta), to industrial use on the Mamquam Delta, site of the sawmill, log handling facilities and former chemical plant. Central Channel and its bordering deltas are of international importance as a staging area for water birds; they are also regionally important as a salmonid nursery and spawning site. Therefore, people’s use of Central Delta (including eastern riparian zone of Squamish River south of Fisherman’s entrance, Training Dyke, Marsh restoration site, East of Fill and western half of Crescent Slough) should be kept to a minimum, and their activities should be governed by spatial and temporal wildlife distribution patterns. Conversely, East Delta would encompass a blend of land uses. Moderate non-motorized recreation is recommended towards Central Channel and in the mature forest connected to the estuary; as Squamish is becoming an increasingly popular site for recreationists, the town would benefit from providing well-regulated, non-motorized access to East Delta because estuaries are outstanding features and favoured hiking destinations. Urban development has not reached full capacity in the vicinity of the town centre, thus there is still room to make choices. A prime choice would be to establish some housing along East Channel, where fish and wildlife values are lower. This type of development would help blend wildlife values with commercial and light industrial use on the western shore of the lower Mamquam Blind Channel, which in turn would tie in nicely with the industrial site and activities across the Blind Channel. Smart-growth planning in the eastern portion of East Delta would help blend human activities with fish and wildlife values, and minimize the displacement of more tolerant wildlife (passerines, reptiles, small and mid-sized mammals).

3.1 Retain Riparian Buffers

As previously mentioned, riparian zones must receive critical concern in all land-planning and management efforts because of their high productivity and multiple roles as wildlife habitat, pollution filters, noise buffers, flood controllers and bank stabilizers. Riparian zones are vulnerable to channel events (e.g., floods) and upslope activities (e.g., human developments) because of their narrow linear nature, their distinctive microclimates and plant communities. As riparian zones interface with aquatic and terrestrial ecosystems, both should be managed as one unit. With the exception of a roughly 400-m reach along Crescent Slough, the entire eastern periphery of the undeveloped portion of Squamish estuary is currently properly buffered from the municipality. With the increasing pressure that accompanies population growth, it is imperative that the buffer remains intact in its entirety, to protect the estuary’s values (including the newly designated Wildlife Management Area). This implies that any urban, commercial and industrial development along Bridge Pond, Cattermole and Crescent Sloughs should be prevented.

The update to Section 26 in the Department of Fisheries and Oceans’ (DFO) Land Development Guidelines makes reference to the Streamside Protection Regulations of the BC Fish Protection Act (SBC 1997, Chapter 21), and should guide decision-making in the estuary. There should be a setback of at least 30 m in the estuary, in areas where the existing streamside vegetation is at least 30 m wide; a minimum buffer of 15 m in width is required where riparian vegetation extends less than 30 m from the top of bank. However, watercourses (their physical and vegetation characteristics, and the presence/absence of fish) should not be the only factor governing buffer width in the Squamish estuary, given the other significant wildlife and habitat features requiring buffer protection, such as the mature forest of Site A, the high meadows and shrubs of East Marsh and North Field, and the areas of exceptionally high structural diversity and species biodiversity (Bridge Pond, Crescent Slough and Upper Mamquam Blind Channel). Although it is rarely possible to protect wide riparian zones in an urban setting, efforts should be made wherever possible to encourage the retention of wider buffers; 45-m buffers can withstand windstorms and protect riparian microclimate conditions from the influence of adjacent, more open habitats (see Brosofske et al. 1997); 75 to 150-m buffers preserve most of the water and riparian wildlife values (e.g., 90% of bird species; Spackman and Hughes1995). The wider the buffer the less probable it will be that adjacent developments will have negative impacts on this regionally significant reserve. A large buffer is particularly critical around Bridge Pond because this area has the highest biodiversity value in the estuary.
Retaining wide riparian buffers also ensures that snags of suitable size and densities are maintained and recruited through time. Snags provide essential habitat for about 85 bird species in North America that use natural cavities, excavate their own, or use holes dug by other species (see Cooperrider et al. 1986). Removal of dead and dying trees within the riparian zone should not be done without consulting an ecologist as well as someone qualified to assess tree hazards. Trees beyond five metres of a road or high public use area can be left alone. If a suppressed tree poses a safety threat, it can be knocked down at a height of three meters, to maintain some of its use to wildlife. Douglas-fir snags remain standing the longest and are least hazardous. Cedar trees are slow to decay but have a tendency to break apart in large blocks. Trees with a diameter at breast height (dbh) of more than 30 cm are less hazardous than small trees, as are broken top, deep-rooted, and vertical trees (Brown 1985). Dolphins and pilings increase local productivity of the water and bottom sediments and should also be left on site, but sawed off at the mudline to prevent erosion from debris accumulations.
Developments that create impervious surfaces, such as roads and parking lots, increase nutrient and contaminant transfer to wetlands. Increased nutrient inputs can cause eutrophication (loss of dissolved oxygen), which creates serious imbalances in the trophic structure of the waters. Nutrients from storm run-off stimulate plant growth (e.g., algal blooms) to the point of anoxia (severe oxygen deficiency). It destabilizes plankton populations, reduces productivity, displaces benthic animals, creates unbalanced food webs, and alters the assemblage of fish and wildlife consumers (Kennish 2002). Cattermole Slough is particularly vulnerable to eutrophication because of its limited flows and small size. Bridge Pond, Cattermole and Crescent Slough are all vulnerable to pollutants. Treating toxic water (e.g., Nexen Site) is far more expensive than stopping pollution at its source. Riparian zones eliminate the need and cost of remediation by ensuring that run-off from roads is directed onto vegetated road shoulders, and stored in and purified within a forest reserve before it enters the water. Storm run-off ponds and other sources of nutrients that aren’t natural, should also have a biofilter (e.g. cattail margin) to reduce nutrient and pollutant input into the water.
If a transportation corridor to the eastern portion of East Delta (Nexen Site) is necessary, it should be established along the east side of the railway from Crescent Slough to the Cattermole Slough crossing; it should then circumvent the east side of an adequately buffered Cattermole slough. A high degree of stratification within a riparian zone (i.e., many vertical layers of vegetation) can increase a buffer’s ability to effectively protect a water body at all levels. For example, retaining or planting cattails, shrubs and trees ensures good bio-filtration, protection against bank erosion, visual cover, and wildlife habitat. Responsible wetland stewards not only retain adequate buffers, but prohibit the isolation of salt marshes by road fills (e.g., Isolated Marsh), ensure continued interchange of fresh and salt water, and minimize wetland acreage covered by road fill - circumventing wetlands where possible. When a road must intersect an estuarine wetland beyond the forest buffers of the periphery, it should be as narrow as possible, it should have numerous drainage structures made of materials resistant to saltwater corrosion, and these structures should be placed at the same elevation as the channels being crossed. Tidal gates should be avoided, and cutbank erosion and sediment production should be minimized (e.g., armouring, grass seeding, mulching, using settling basins during construction if necessary)(see B.C. Ministries of Forests and Environment 1995b). At the very least, an impact assessment should be done before the municipality commits to building a transportation corridor through East Delta.