The Skeena River Estuary

Chatham Sound

Chatham Sound is situated in the northern part of British Columbia, located between Dundas and Stephens Islands and the Tsimpsean Peninsula near Prince Rupert and bordering on Alaska. It is a semi-enclosed basin with an area of approximately 1500 km2, and is influenced by fresh water from two large rivers, the Skeena and the Nass (Trites, 1956).

The Nass River discharges into Portland Inlet, and fresh water flows from there into the northern end of Chatham Sound and eventually out through Dixon Entrance (Tera Planning Ltd., 1993). Water from the Skeena River enters Chatham Sound through a series of channels. Approximately 75% of the Skeena River flows equally through Marcus Passage (separating Smith and DeHorsey Islands from Kennedy Island) and Telegraph Passage, while the remaining 25% of the Skeena River flows through Inverness Passage (Trites, 1956). As a result of the fresh water discharges of the Nass and Skeena Rivers, the whole of Chatham Sound is essentially a large estuary (Tera Planning Ltd., 1993). Generally, estuarine circulation occurs when a large volume of fresh water from a river flows out along the surface at the head of an inlet. As it moves seaward, this layer entrains saline water from the layer beneath it, and carries this entrained water seaward. The loss of water from the lower layer is replenished by a deep water flow which has a net landward movement. However, as a result of the fresh water influx from two rivers, a highly irregular coastline, and a large horizontal extent, the circulation patterns in Chatham Sound are considerably more complex than most coastal BC inlets (Tera Planning Ltd., 1993).

The Skeena River

The Skeena River originates high in the coastal mountains of northwestern British Columbia, at the edge of the Spatsizi Plateau, and flows 570 km to reach the Pacific Ocean. Draining a total area of 54,400 km2, the Skeena is the second largest river in the province, and one of the longest un-dammed rivers in the world.

Skeena River.

The Skeena River Estuary

Aerial view of Chatham Sound. Photo: Brian Huntington

The Skeena River estuary is a unique system in that it does not have a single distinct intertidal delta typical of most estuary systems (Hoos, 1975). Suspended sediments from the Skeena River are deposited in shoals along the lower river and the channels which connect the estuary to the open ocean.This creates a region of extensive mudflats and shallow, intertidal passages around DeHorsey Island, through Inverness Passage, and between Kitson Island and Lelu Island (Flora Bank).

Skeena River estuary.

These mudflats and intertidal areas have been identified by the North Coast Wetlands Program as important migratory/wintering waterfowl habitat. Several rare species, including the red-listed western grebe and the blue-listed trumpeter swan, brant, oldsquaw and great blue heron have all been recorded in the wetlands. A Department of Fisheries and Oceans fisheries habitat study identified Inverness Passage, Flora Bank, and DeHorsey Passage, in that order, as critical habitats for Skeena River juvenile salmon, as well as important eulachon habitat (Higgins and Schouwenburg, 1973).

Concerns

Although estuaries provide essential nursery and juvenile rearing habitats, with up to 80% of coastal wildlife species relying on estuaries during at least one stage of their life history (BCMOE, 2006), they frequently occur in areas which are highly valued for development. The Port of Prince Rupert has recently entered an expansion phase in its industrial development, starting in 2004 when the Northland Cruise Terminal was constructed, and followed in 2007 by the construction of the Prince Rupert Container Terminal (Maher Terminals) at Fairview. Many more projects are on the horizon, such as the Pinnacle Renewable Energy pellet export terminal (construction underway), the Ridley Terminal Inc. coal port expansion (construction underway), the Pacific Northwest LNG terminal on Lelu Island (construction planned for 2015 to 2018), the Prince Rupert LNG terminal on Ridley Island (construction planned for 2015 to 2020), the Canpotex Potash export terminal (construction planned for 2014 to 2017), and the Maher Terminal’s Fairview terminal phase 2 expansion project (construction start unknown). Increased vessel traffic associated with these planned terminals, as well as potential oil tanker activity from proposed projects such as the Enbridge Northern Gateway, will increase the possibility of spills and other marine accidents. Clearly, estuaries represent an area where there is conflict between human resource need and environmental sustainability. This is further exacerbated by a site-by-site approach to habitat protection, which often saves sensitive habitat from destruction by one project only to have the same piece of habitat threatened by a neighboring project. A more holistic approach to habitat protection is required, one which is based on a comprehensive and scientifically rigorous understanding of the roles and vulnerabilities of the different species and habitats in the estuarine environment. In order to implement this approach, there is a need to better understand the cumulative, and often complex, anthropogenic impacts on estuarine environments.

To view a series of panorama images showing the locations of the various development sites relative to the major features of the Skeena River estuary, click on the image below.

Facilities on Ridley Island. Photo: Brian Huntington. Click image to view panorama photos of the Skeena River estuary.

Next Steps

A number of local environmental organizations and community groups are working together to try to protect the Skeena River estuary from poorly planned over-development, and to establish the framework nessary to create a Skeena River estuary management plan. In order to do this, these various organizations are attempting to address issues, through research, data analysis, and modeling, such as:

  • Insufficient knowledge of the locations of many ecologically important, sensitive, and/or vulnerable habitats.
  • Lack of necessary baseline data on concerns such as ecologically important (e.g., keystone species), sensitive, and/or vulnerable species, sediment transport, sediment chemistry, and cumulative impacts, required for sound marine planning.
  • Lack of understanding of the processes, such as ocean circulation and primary and secondary production, which control the distribution of species and habitats within Chatham sound.
  • Lack of understanding of how global climate change will impact Chatham Sound and the Skeena River estuary.

References

BCMOE (Ministry of Environment) 2006. Alive and Inseparable. British Columbia’s Coastal Environment: 2006.

Higgins, R.J. & Schouwenburg, W.J. 1973. A biological assessment of fish utilization of the Skeena River estuary, with special reference to port development in Prince Rupert. Dept. of Envir., Fish. & Mar. Ser. Tech. Rep. 1973-1.

Hoos, L.M. 1975. The Skeena River estuary status of environmental knowledge to 1975. Special Estuary Series No. 3. Environment Canada, Vancouver, BC, 418 pp.

Tera Planning Ltd. 1993. Bulk Liquids Terminal South Kaien Island Prince Rupert, BC: Volume II – Environmental Report. Consultant report for Prince Rupert Port Corporation.

Trites, R.W. 1956. The Oceanography of Chatham Sound, British Columbia. J. Fish Res. Bd. Canada 13(3):385-434.

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