Your Pretty River flood risk comes down to two facts about your own lot: whether the Nottawasaga Valley Conservation Authority maps it as regulated, and whether it sits behind the Pretty River Dike or on the river side of it. You can find the first in about ten minutes on the NVCA’s own map. The second tells you what kind of flood you are actually exposed to, and it is rarely the one people picture.
Why Collingwood has this question at all
The NVCA’s own description is blunt. The town was built on a shallow floodplain, and it floods. The two floods it names are the Victoria Day flood of 1912, photographed near Third and Birch, and the St. Patrick’s Day flood of 1942, photographed on Hume Street. Both happened before there was any dike.
The Pretty River is one of four major watercourses through the town. It rises on the Niagara Escarpment in Clearview, runs down the Pretty River Valley, and is held by the dike from the point it enters town until it reaches Nottawasaga Bay. The dike went in during the 1970s, and the NVCA credits it, with the Black Ash Creek Floodway, for keeping the low-lying parts of Collingwood out of the water. The route it takes and why it matters to a basement are set out on our page about water damage restoration in Collingwood, so this post sticks to the narrower question of your lot.
Check your own lot before you worry about the river
The NVCA says property owners should find out well ahead of time whether they are in a floodplain or another natural hazard area. It gives you the tool to do it.
- Open the NVCA Interactive Data Viewer from its Find Your Property page.
- Use the search box in the upper right corner, type the address, and press Enter.
- See whether the lot falls inside the regulated area. If the map will not load, the NVCA suggests clearing your browser cache.
- If the answer is yes, or unclear, submit a General Inquiry on the NVCA e-permitting platform. Staff review the property and may ask for more detail or an appointment.
Do this in autumn, when nobody at the NVCA is busy with a flood. A regulated area is not a prediction that you will flood. It is the area where the NVCA controls development because of a hazard, and on a river that hazard is usually flooding, erosion or both.
Three positions, three different risks
Behind the dike, downtown. This is the protected ground. The dike is built to contain the floodwaters of the Provincial Regulatory Storm Event, a storm with under a 1% chance in any year. The NVCA is careful with its own wording here: it protects the town “when maintained properly”. The NVCA removed vegetation from the dike between 2021 and 2025. In 2026 it is running a safety review, with two weeks of borehole drilling in June and equipment to monitor pressure inside the structure. None of that is a warning. It is a flood control structure from the 1970s being checked, and the review will set the repair list for the coming years.
What behind the dike means in practice is that the river is unlikely to be your problem. The water that does reach basements on low ground here comes from elsewhere, and the area page covers those routes.
On the river side, or up the valley. A lot next to the channel, or upstream in the Pretty River Valley where the dike does not reach, is the position the regulated area exists for. The NVCA describes floodplains as the land where a river stores water when heavy rain or snowmelt pushes it over its banks. It also notes that river banks move over time as the outer bank erodes, which is why it regulates a meander belt and not only the water line. If your lot touches the Pretty, the map lookup above is the whole answer, and it is worth doing before you finish a basement.
Near the mouth, on the bay. The dike ends near the shore of Nottawasaga Bay. Lots along the Georgian Bay shoreline carry a different hazard: the NVCA says they are prone to shoreline flooding when lake levels are high, and waves do damage that river water does not. That is a lake question, not a Pretty River one, and the same map shows it.
When floods come
Floods in this watershed are not a spring-only event. For Collingwood’s flood season months, the NVCA lists the spring melt, major rainstorms in summer and autumn, and rapid winter snowmelt or an ice jam. On a river that runs off the escarpment, a warm rain on snow in March is the pattern to respect, and it rarely arrives unannounced: the NVCA issues graded flood messages when its forecasts show a flood risk. Our page on flood cleanup in Collingwood explains what each message level asks of you.
What to line up before you need it
The question behind this search is usually whether to have somebody ready. Here is the short list, in the order it pays off.
- The map answer, written down. Whether your lot is regulated changes what happens after a flood, not only before one.
- The policy answer. River water in a basement is overland water to an insurer. Work through should I claim water damage insurance in Ontario for your own policy before spring, not after the water arrives.
- The permit answer. The NVCA states that if river or shoreline flooding damages a development in its regulated area, the owner must get an NVCA permit to repair it. Ask the NVCA before you rebuild on a regulated lot, not after.
- The first hour, rehearsed. A river flood has no valve to shut. What to do after water damage sets out the order: power, photographs, then moving things.
One thing does not change with your side of the dike. Water that reached the house across open ground is handled as contaminated, so soft flooring it soaked is removed rather than dried.
Where to go from here
If the map puts you in the regulated area, or you are behind the dike and want to know what does put water in basements on that ground, start with the Collingwood area page linked above. If you are dealing with water now, the basement flooding in Collingwood page covers what the work involves.