2025-12-16b - South Branch Raisin River Flood Mapping Project

The Raisin Region Conservation Authority (RRCA) recently received funding through the Flood Hazard Identification and Mapping Program (FHIMP) to update flood hazard mapping. The RRCA seeks to have the flood hazard of the South Branch of the Raisin River watershed assessed and mapped in accordance with the current Federal Flood Mapping Guidelines and provincial requirements for regulatory flood mapping.
The South Branch of the Raisin River watershed study area includes areas of the City of Cornwall and the Township of South Stormont (within the United Counties of Stormont, Dundas and Glengarry). The study area includes the South Branch of the Raisin River from the headwaters, north of County Road 36, to the downstream limit at Boundary Road and includes the Henderson Drain, Cardinal Drain and Boales Drain. The study area has a watershed area of 55 km2, and its main channel is 47 km long. The South Branch joins the Main Branch, Raisin River, then ultimately discharges into the St. Lawrence River. One Water Survey of Canada station is located in the study area (02MC030, South Branch, Raisin River).