Welcome to the new era of online flood maps

The organization responsible for flood risk mitigation in and near Kitchener, Ont. is contemplating enabling online access to maps that would let some clients see whether they are in a high-risk flood zone.

For the Grand River Conservation Authority (GRCA), the ultimate aim is for some clients to be able to go to a website and see whether their property is in, for example, a 50- or 100-year flood zone.

“It [would] be along selected reaches where we map that product,” said Dwight Boyd, GRCA’s director of engineering, in an interview. “So we would likely be looking along the main rivers – the Grand River, the Conestoga River and the Speed River.”

Flooding of the Grand River in February 2018 affected numerous properties, including some in Brantford.

The Grand River watershed – the area in which GRCA helps manage flood risk – includes Kitchener, Waterloo, Cambridge, Guelph and Brantford. It goes all the way southeast to Dunnville, where the Grand River drains into Lake Erie. GRCA is one of Ontario’s 36 conservation authorities.

“In recent years, new technology has been coming along that is really allowing us to approach updating our floodplain mapping in a much different way,” said Boyd. For example, GRCA used light detection and ranging (LiDAR) to create maps depicting elevation throughout the watershed. That was a project funded by the Ontario ministry of agriculture, food and rural affairs, between 2017 and 2018, said Boyd.

“In the future we will likely look at – through either our website or the municipal websites – some of the new flood zone products but we have to work with our insurer to demonstrate the processes we have in place and the reliability of that information before we make that available,” said Boyd. “That is something that we are working through. We want to provide useful information to the general public and emergency responders.”

In a federally-funded project in 2018, GRCA used LiDAR bathymetry to map underneath the surface of some parts of the Grand River. That was a “proof of concept,” that will provide a basis for GRCA to update its flood mapping, said Boyd. “From that, our engineers can extract information to update our hydraulic models and our hydrology. This is used to help us estimate and forecast flood flows.”

GRCA announced May 27 it will do a flood mitigation study in the community of New Hamburg, between Stratford and Kitchener. The total cost is about $180,000, with $90,000 of that coming from Ottawa.

GRCA anticipates that study will provide updated flood zone mapping for New Hamburg.

As of press deadline, it is not known if or when the online flood maps will be made available.

“Up until now a lot of our floodplain mapping has been hard copy,” said Boyd. “The original floodplain mapping was mapped to come up with a line for development regulation purposes whereas the new digital floodplain mapping is looking at new products like flood risk mapping that maps the potential for flooding. So where is the 1% chance line? Where is the 2% chance line for flooding in any given year?”