Conservationists work to update flood risk map along Ottawa River

Ottawa's flood risk map is getting a long overdue update by the South Nation Conservation group after learning it hasn't been updated in years. The Ottawa River is the main target, and is getting an assessment for flooding and erosion. The city of Ottawa is funding the project, and the draft of the map will be released in the spring.

Mapping natural hazards ensures that new developments can proceed safely and sustainably

Rocks on the banks of the Ottawa River.
By assessing the flood and erosion risk along the Ottawa River, developers will be able to use the data to better plan and build safely. (Denis Babin/CBC)

A conservation authority is working to update flood hazard maps for parts of eastern Ontario, which will help municipal governments assess the risk of flooding when planning for the future.

The South Nation Conservation (SNC), an organization dedicated to the protection and restoration of ecosystems in the region, is leading the efforts to update the maps, which hasn't been done for many years.

The organization is surveying the Ontario side of the Ottawa River between the city of Clarence-Rockland and the Quebec-Ontario border, east of Chute-à-Blondeau, along with areas crossed by Bear Creek, east of downtown Ottawa. 
A flood zone along the Ottawa River, illustrated with blue hatching, near Rockland, Ont. (United Counties of Prescott and Russell)

Since the end of the summer, a SNC team has been scanning the river and creek to measure their depth and width, as well as the dimensions of bridges and culverts built along the two water bodies.

An analysis of the data collected in the field will help determine which areas are the most likely to flood and be affected by soil erosion.

"This will allow us to establish the limits of the flood zones, that is to say the extent of land that can be occupied by water in the event that [the Ottawa River and Bear Creek] overflow," Jason Symington, an environmental technician with the SNC told Radio-Canada.

Incomplete portrait

Funding for the surveys comes from the federal government's Natural Disaster Mitigation Program, along with the City of Ottawa and the United Counties of Prescott and Russell (UCPR).

According to Louis Prévost, director of urban planning and forestry with the UCPR, the overhaul of the flood risk maps is long overdue and will fill in a large piece of the Ottawa River puzzle. 

"We basically have flood plain mapping for all of the other major watercourses within the counties. We've got good coverage, but the Ottawa River was lacking big time," he said.

Prévost said the mapping will be a "tremendous tool" for city planners. Once the flood plains are identified in the official county plan, that information will be used to create local zoning bylaws to eliminate any potential developments in flood-prone areas, he said.

There currently aren't any studies to precisely ensure that when a municipality allows a new construction to go forward, that it won't be within a flood plain. (Denis Babin/CBC)

Valuable tool for municipalities

With access to precise data, municipalities in the region will be better able to plan any prospective development. 

Jeanne Charlebois, the former mayor of Hawkesbury, Ont., said not having flood plain information readily available is holding back commercial and residential development along part of the city's waterfront — what she calls a "prime piece of land."

"We will be able to tell the people who own land on the waterfront and want to develop it, 'Here you go. Here's step one. Step one is you're no longer in a flood plain, or sadly you are in a flood plain and this is what you're going to have to do,'" she said.

Charlebois said Hawkesbury's future growth lies in the city's west end, and the sooner the municipality has the information to safely develop, the better. 

Drafts of the planning maps are expected to be completed by March 2022 and shared during public consultations.

With files from Radio-Canada's Denis Babin