Canadian Extreme Water Level Adaptation Tool (CAN-EWLAT)
Extreme water level along the marine coastline is a result of a combination of storm surge, tides, and ocean waves. Future projections of climate change in the marine environment indicate that rising sea level and declining sea ice will cause changes in extreme water levels, which will impact Canada's coastlines and the infrastructure in these areas. Understanding these changes is essential for developing adaptation strategies that can minimize the harmful effects that may result.
CAN-EWLAT is a science-based planning tool for climate change adaptation of coastal infrastructure related to future water-level extremes and changes in wave climate. The tool includes two main components: 1) vertical allowance and 2) wave climate. CAN-EWLAT was developed primarily for DFO Small Craft Harbours (SCH) locations, but it should prove useful for coastal planners dealing with infrastructure along Canada’s ocean coastlines.
Note: In February 2020, we have updated the web site to incorporate new data on the west coast of Canada from a storm surge hindcast (Zhai et al, 2019). We have also changed the future scenarios presented to be the IPCC AR5 low (RCP2.6) and high (RCP8.5) projections.
Vertical allowances are recommended changes in the elevation of coastal infrastructure required to maintain the current level of flooding risk in a future scenario of sea level rise. These estimates are based on a combination of the following two elements:
- The future projections of regional sea level rise along with the uncertainties in those projections. The uncertainty is captured by the statistical distribution (defined by the 5-percentile to 95-percentile limits) of the IPCC AR5 projections of regional sea-level change for the 21st century for the RCP2.6 (low) and RCP8.5 (high) emission scenarios. CAN-EWLAT improves upon the IPCC AR5 projections by incorporating information on land subsidence measured with high-precision GPS instruments.
- Historical water level records including both tides and storm surge (referred to as storm tides) at tide gauge sites. At SCH sites with no tide gauge records available, we use storm-surge model to simulate storm tides (Bernier and Thompson, 2006; Zhang and Sheng, 2013; Zhai et al, 2019). It is important to note that the vertical allowance provided by CAN-EWLAT is based on historical records and does not incorporate predicted changes in storm tides over the coming century because the current state of knowledge of future projections of storminess is limited.
Vertical allowances are not provided for the SCH sites located upstream of New Westminster in Fraser River and upstream of Quebec City in the Saint Lawrence River since those sites are influenced more by river flooding than storm surge.
Ocean waves are generated and developed in response to winds. Often the largest waves result from marine storms, for example, extra-tropical hurricanes propagating towards the northeast, along the North American coastline, or nor’easters, propagating from Cape Hatteras towards Newfoundland and beyond. The largest waves result from the largest winds, blowing over long fetches.
North Atlantic storms are expected to experience minor changes over the next fifty years, which could result in a small change to the wave climate. However, with warming air temperatures projected over the coming century, possibly the largest change in wave climate would result from changes in sea ice in coastal areas of Canada. For example, if the Gulf of St. Lawrence has significantly less sea ice in the future, the winter wave climate would be significantly different than at present where the waves are small, or non-existent, in the winter. In this case, waves could significantly impact coastal erosion, infrastructure, and winter marine activities.
Bernier, N. B., and K. R. Thompson, 2006. Predicting the frequency of storm surges and extreme sea levels in the northwest Atlantic, J. Geophys. Res., 111, C10009, doi:10.1029/2005JC003168.
Han G., Z. Ma, L. Zhai, B. Greenan and R. Thomson 2016. Twenty-first century mean sea level rise scenarios for Canada. Can. Tech. Rep. Hydrogr. Ocean. Sci. 313: x + 19 pp.
Parris, A., P. Bromirski, V. Burkett, D. Cayan, M. Culver, J. Hall, R. Horton, K. Knuuti, R. Moss, J. Obeysekera, A. Sallenger, and J. Weiss, 2012. Global sea level rise scenarios for the US National Climate Assessment. NOAA Tech Memo OAR CPO-1. 37 pp.
Robin, C., S. Nudds, P. MacAulay, A. Godin, B. De Lange Boom and J. Bartlett (2016) Hydrographic Vertical Separation Surfaces (HyVSEPs) for the Tidal Waters of Canada, Marine Geodesy, 39:2, 195-222, DOI: 10.1080/01490419.2016.1160011
Zhai L., B. Greenan, J. Hunter, T.S. James, G. Han, P. MacAulay and J. Henton, 2015. Estimating sea-level allowances for Atlantic Canada using the Fifth Assessment Report of the IPCC. Atmosphere-Ocean, http://dx.doi.org/10.1080/07055900.2015.1106401.
Zhai L., B. Greenan, J. Hunter, G. Han, R. Thomson, and P. MacAulay 2014. Estimating Sea-level Allowances for the coasts of Canada and the adjacent United States using the Fifth Assessment Report of the IPCC. Can. Tech. Rep. Hydrogr. Ocean. Sci. 300: v + 146 pp.
Zhang, H., and J. Sheng, 2013, Estimation of extreme sea levels over the eastern continental shelf of North America, J. Geophys. Res. Oceans, 118, 6253–6273, doi:10.1002/2013JC009160.
Zhai, L., B. Greenan, R. Thomson, and S. Tinis, 2019. Use of Oceanic Reanalysis to Improve Estimates of Extreme Storm Surge. Journal of Atmospheric and Oceanic Technology, 36, 2205-2219, https://doi.org/10.1175/JTECH-D-19-0015.1
If you are unfamiliar with any of the abbreviations and technical terms above, please see the Glossary of Terms.
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