Adaptation Planning
Case Study: Delta, BC
About the Case Study
Community Context
Climate-related Changes
Community Impacts
Adaptation Actions
More Information
About the Case Study
Natural Resources Canada (NRCan) formed a team of scientists to work with the community of Delta, the Tsawwassen First Nation and other stakeholders to investigate the potential impacts of rising average sea level and extreme sea levels on Roberts Bank, a tidal flat that forms a boundary for the communities of Delta and Tsawwassen. The findings of the study directly inform these communities of their potential risks and impacts arising from climate change. This summary is based on NRCan’s Delta Municipal Case Study, one of five in NRCan’s Municipal Case Study series: Climate Change and the Planning Process (see More Information About... at the end of this document).
COMMUNITY CONTEXT
The Corporation of Delta is a low-lying coastal community on the Fraser River delta that is protected from river and storm-surge flooding by dykes along the river and shoreline. The nearby tidal flats, rich with extensive beds of eelgrass, are an important habitat for birds and fish. Delta, with a population of approximately 103,000, is one of 22 municipalities in Metro Vancouver — population 2.1 million. The City is located in a highly productive agricultural area and almost half of the City’s land base is used for agriculture.
Two important structures are located in the area: Vancouver Port Authority’s causeway leading to the Delta Port shipping terminal and BC Ferries Corporation’s Tsawwassen Terminal also reached by causeway.
CLIMATE-RELATED CHANGES
Sea Level Rise
Average sea level is projected to rise between 0.35 and 1.20m by 2100 in the Fraser River Delta area1. This projected range takes into account global average sea level rise — from melting of ice caps and glaciers, and warming of the upper ocean — as well as local effects that include vertical movements of the earth, for example, uplift due to moving tectonic plates, and subsidence, typically occurring at river deltas and caused when sediments carried by moving rivers are deposited on the delta.
Increased intensity of storms
Globally, storms are projected to increase in frequency and severity as a consequence of climate change. Extreme storm events can result in sea levels reaching one metre above the predicted high tide level1. The potential impacts of such future events are illustrated by a storm that hit Delta in February 2006. The City experienced an unusually high tide that combined with high winds of more than 80 km per hour to create a storm surge. The water level in Boundary Bay, to the southeast of the City, rose 0.914 to 5.55 metres above the predicted level, breaching the sand berm and damaging more than 200 homes.
Community Impacts
As sea level rises in the area around Delta, salt water will migrate further inland, inundating agricultural land, eroding marshes and mudflats, and putting additional stress on the municipality’s infrastructure. Some of the key concerns among Delta residents and stakeholder groups include the following.
Loss of Fish and Bird Habitat
The rich ecosystems on Roberts Bank tidal flats are bracketed by a dyke system on one side and the ocean on the other. Under natural conditions, sea level rise would cause the tidal flats to migrate inland, but with dykes preventing this inland movement the tidal flats shrink as they are squeezed against the dykes. Intense storms will amplify the erosion of marshes, leading to an important loss of food and habitat for birds and fish.
Potential Undermining of Dyke System
Delta’s dyke infrastructure is at risk of being undermined which could result in subsidence of the dykes and saltwater flooding of low lying areas.
Causeways and Port Facilities at Risk
The Vancouver Port Authority’s Delta Port shipping terminal and BC Ferries Corporation’s Tsawwassen Ferry Terminal are important contributors to the Province’s economy and transportation infrastructure. They both have major infrastructure, including causeways that are exposed to ocean action.
Possibility of Compromised Irrigation System
The effects of rising sea level could also compromise the community’s irrigation system when sea levels are higher than the drainage ditches and storm sewers that are working to direct water away.
Deteriorated Water Supply
Saltwater may find its way into the freshwater supply, degrading quality and quantity not only for agricultural operations, but also potentially affecting the municipality’s water supply.
Adaptation Actions
As a result of the Roberts Bank study, the Mayor of Delta took action to make climate change and its effects on the City a priority over the next three years.
Rise sea level and related effects are being considered in a re-evaluation of the dyke design.
A preliminary set of climate change impact indicators to support future adaptation planning has been developed, including biophysical, ecological, socio-economic, infrastructure and cultural indicators. Some examples of these could include: sea-level rise, changes in populations of migratory birds and costs caused by flood damage to property.
Preliminary options for adaptation include:
- Reinforce dykes using additional engineered structures, eg. berms, rip-rap and seawalls;
- Move the dyke system inland, creating opportunity for low-lying land to flood and re-establish itself as a rich ecosystem and habitat;
- Nourish tidal flats by removing log debris and extending water channels into the area. This will allow better saltwater flushing of the area and improve fish access;
- Enhance sub-tidal rock reefs on Roberts Bank to create new habitat for fish and wildlife.
More Information
Delta Municipal Case Study
This summary draws on NRCan’s Delta Municipal Case Study, one of five in NRCan’s Municipal Case Study series: Climate Change and the Planning Process. The five case studies are available on the Canadian Institute of Planners website
Additional information about the municipal case studies’ research studies is available on NRCan’s website
Delta Case Study and climate change impacts in British Columbia
The British Columbia chapter (Chapter 8) in Canada’s climate change assessment report, From Impacts to Adaptation: Canada in a Changing Climate 2007 provided material for this case study summary: http://adaptation.nrcan.gc.ca/assess/2007/index_e.php
Projected sea level rise in British Columbia
Summary Report — Bornhold, Brian D, (2008). Projected Sea Level Changes for British Columbia in the 21st Century. This report is a summary of a study by the Government of Canada and the first comprehensive analysis of sea level change for B.C.’s coast since 1997. It was released by the Province of BC in December 2008.
Full Technical Report — R.E. Thomson, B.D. Bornhold and S. Mazzotti (2008). An Examination of the Factors Affecting Relative and Absolute Sea Level Rise in British Columbia. Canadian Technical Report of Hydrography and Ocean Sciences 260, Fisheries and Oceans Canada (2008).
Visualizing the impacts of climate change on BC communities
The University of British Columbia’s Local Climate Change Visioning Project creates vivid 3D visualizations of communities in the future, under climate change conditions, bringing home to residents what the impacts of global warming might look like in their own backyards. Delta is the subject of one such visual exploration. For more information contact Ellen Pond (epond@interchange.ubc.ca), Kristi Tatebe (kmtatebe@interchange.ubc.ca), or David Flanders (flanders@interchange.ubc.ca).
Indicators of Climate Change Impacts
Gregory, R., Failing, L. and Arvai, J. (2006). Indicators for Climate Change at Roberts Bank. Unpublished report prepared for Natural Resources Canada, Earth Sciences Sector, 20 p. For more information contact Robin Gregory, Value Scope Research & Decision Research, 1160 Devina Drive, Galiano, B.C. V0N 1P0. Email: rgregory@interchange.ubc.ca.
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