2025 Lower Conestogo Floodplain Mapping Update
The Grand River Conservation Authority is undertaking a project to update floodplain mapping for the Conestogo River between the Conestogo Dam and the Grand River. Which will result in amendments to GRCA's regulated area mapping under Ontario Regulation 41/24.
Background:
As outlined in a staff report titled “Lower Conestogo Floodplain Mapping Update ”, a project was carried out under the federal National Damage Mitigation Program (NDMP) to complete work necessary to update floodplain mapping for the Lower Conestogo River between Conestogo Dam near Glen Allan to where it meets the Grand River near the Village of Conestogo. The study area includes the Townships of Mapleton, Wellesley and Woolwich as shown in Figures 1 to 4.
The work completed for the floodplain mapping updates included the completion of detailed hydraulic structures survey of all bridge and culvert crossings in this section of the Conestogo River, as well as surveying the shape of the river channel below the water surface. This new data was used to create a hydraulic model, which simulates how flood waters will move through the river and over land to determine what areas will flood based on a given flow. An existing hydrologic model generates the amount of water (flow) anticipated during a storm event. Output from the new hydraulic model was combined with modern topographical data and flows to update the extent of the Regulatory Floodplain in the lower Conestogo River.
Public feedback was requested between August 22nd to October 24th. Two public information meetings were held in September. The materials from the public information meetings can be found below.
Final proposed floodlines incorporate feedback received through public consultation and are shown in Figures 1 to 4. The proposed floodplain changes will be presented to the General Membership of the GRCA on November 28th for their approval.
If approved, GRCA's regulatory mapping available through the “Map your Property ” tool will be amended to reflect the updated floodplain and its 15 metre allowance.
Public Information Materials
A virtual public meeting was held on Monday, September 22, 2025, at 7:00 pm.
An in-person public meeting was held on Thursday, September 25, 2025 at the Woolwich Memorial Centre (24 Snyder Avenue South, Elmira N2B 1Y9) from 5:00 pm to 7:30 pm, with a presentation at 6:00 pm.
Video of September 22 2025 Presentation
Information Handout from September 25 2025
Download the GRCA’s Proposed Regulatory Mapping Change Public Information Meeting Handout for more information on the proposed changes.
Lower Conestogo River Floodplain Mapping Update Map 1 of 4
Lower Conestogo River Floodplain Mapping Update Map 2 of 4
Lower Conestogo River Floodplain Mapping Update Map 3 of 4
Lower Conestogo River Floodplain Mapping Update Map 4 of 4
Lower Conestogo River Floodplain Mapping Update Map 2 of 4Lower Conestogo River Floodplain Mapping Update Map 3 of 4Lower Conestogo River Floodplain Mapping Update Map 4 of 4Final Proposed Floodlines
Figure 1: Lower Conestogo River Floodplain Mapping Update Map 1 of 4
Download Lower Conestogo River Floodplain Mapping Update Map 1 of 4 (10002 KB) to see Figure 1 in greater resolution.
Figure 2: Lower Conestogo River Floodplain Mapping Update Map 2 of 4
Download Lower Conestogo River Floodplain Mapping Update Map 2 of 4 (9088 KB) to see Figure 2 in greater resolution.
Figure 3: Lower Conestogo River Floodplain Mapping Update Map 3 of 4
Download Lower Conestogo River Floodplain Mapping Update Map 3 of 4 (9170 KB) to see Figure 3 in greater resolution.
Figure 4: Lower Conestogo River Floodplain Mapping Update Map 4 of 4
Download Lower Conestogo River Floodplain Mapping Update Map 4 of 4 (11611 KB) to see Figure 4 in greater resolution.
If you have questions, please contact Beth Brown at 519-621-2763 extension 2307 (bbrown@grandriver.ca).
Contact Us
Grand River Conservation Authority
400 Clyde Road, PO Box 729
Cambridge, ON
N1R 5W6
Phone: 519-621-2761
Toll Free: 1-866-900-4722
grca@grandriver.ca