Maps will detail impact of sea level rise on Valley coastline

It could be argued that climate change hasn’t yet impacted the daily lives of people in the Comox Valley. Yes, it has been drier for longer periods and a year ago the smoke from forest fires dimmed our skies and filled our lungs. The Comox Glacier is disappearing before our eyes.

These are minor events, however, compared to the torrential rains, flooding, droughts and intense super-hurricanes inflicting damage to other parts of the world.

But the serious consequences of climate change will soon reach our idyllic part of the world in the form of sea level rise.

Sea levels have risen by almost eight inches since the 1890s, an annual rate of about 0.06 inches per year, an amount barely noticeable except to those paying close attention.

But the rate of sea level rise has accelerated to 0.14 inches per year since 2006, and scientists predict it will continue to speed up as global temperatures climb.

The latest dire warnings suggest sea level could rise by as much as 1.3 feet by 2050 and up to 8.2 feet (2.5 metres) by 2100, depending on the success of global efforts to reduce greenhouse gas emissions.

FOCUS ON COMOX VALLEY IMPACTS

To determine how rising sea levels will affect the Comox Valley coastline, the Comox Valley Regional District is undertaking detailed mapping of the regions 200 kilometres of coastline, from the Oyster River to Fanny Bay, including Denman and Hornby islands.

With a $500,000 grant from the National Disaster Mitigation Program, the CVRD hired Kerr Wood Leidal consulting engineers to assess the coastline from a geological perspective. They will produce maps and supporting technical data for five scenarios of sea level rise in the years 2030, 2050, 2100, 2150 and 2200.

The report will be a helpful planning guide for emergency management as well as for new development. And, the information will inform the CVRD how to make corresponding policy and regulatory changes, such as floodplain construction levels and setbacks.

The data will also help the CVRD predict how much flooding will occur and how long each flooding event will last.

“Sea level rise is coming whether we think it is or not and governments are being asked to act,” Alana Mullaly, the CVRD’s senior manager of the Regional Growth Strategy and sustainability, told Decafnation. “This will create a lot of hard conversations.”

With rising sea levels pouring over portions of our coastline, how close to the foreshore should building be allowed? Where should local governments put new infrastructure? How should local government manage its assets, such as parkland and archaeological sites? Who will pay for the restoration or relocation of assets?

Sea levels most certainly will have an effect on future land use planning.

“The CVRD may get a request to put a park here or a development there, but that property may be underwater in 20 years,” Mullaly said. “I’m thinking about the weighing of values that we, as a community, will need to do in dealing with climate change.”

RICHER DATA FOR ENGINEERS

To do this coastal flood mapping, the consultants will use LIDAR (Light Detecting and Ranging) to survey land remotely and produce high resolution topographic contours. The province has already flown LIDAR equipment over our area to collect the raw survey data and the consultants will process the data for use in the development of hundreds of maps.

Right now, communities that do not have coastal flood mapping generally rely on the requirements set by the province, which are based on mapping from the 1970s and 1980s.

Those maps did not account for any sea level rise, and neither does the current CVRD floodplain bylaw.

But by professional code, once engineers know something they have to consider it, and they have been taking sea level rise into account based on limited information. This report will give engineers richer local data.

Coastal flood mapping will put the CVRD in compliance with the Coastal Food Hazard Guideline, which is the main resource for engineers designing construction projects.

WHAT IT MEANS FOR THE PUBLIC

After the report is delivered by March 31 next year, the CVRD will hold public engagement events to inform citizens of its findings, which will ultimately lead to
recommendations for bylaws and other relevant regulations and guidelines.

“Sometimes it has been difficult for citizens to pinpoint the source or motivation when government rules change,” Mullaly said. “This won’t be one of them. This is not an arbitrary change. Sea level rise is coming.”

HOW HIGH WILL SEAS RISE?

The provincial government’s official prediction for sea level rise is a half-metre by 2050, one metre (just over three feet) by 2100 and two metres (about 6.5 feet) by 2200.

But that’s too low by at least half, according to recent scientific studies and the consulting engineers who did a similar mapping project for the City of Campbell River.

Northwest Hydraulic Consultants told Campbell River that the province’s projection “might be conservative.” One of the firm’s engineers, Grant Lamont, said it depends on future greenhouse gas emissions and how quickly ocean warming expands.

The loss of polar ice will accelerate in the second half of the century, Lamont said, and force people to cope with larger changes in shorter periods of time.

He recommended planning for two metres of sea level rise by 2100, as the states of California and New York have done.

Campbell River’s report suggests flooding will threaten downtown streets and buildings, and that local governments purchase coastal properties and turn them into pre-flooded parkland.