Photo: Fall River at Bennet Lake Dam

Floodplains are low-lying areas adjacent to watercourses that are prone to flooding and can experience unstable slopes due to erosion. In eastern Ontario, the 1:100-year floodplain standard is used to identify lands at risk of flooding. Conservation Authorities in Ontario, including the Mississippi Valley Conservation Authority (MVCA), play a key role in floodplain management. This responsibility is primarily carried out through the requisition of engineered floodplain mapping and supporting documentation.

Project Background

The Fall River is a major watershed within the jurisdiction of the Mississippi Valley Conservation Authority (MVCA). This watershed has experienced notable flood events in recent years, including in 2019, 2017, 2014, 2008, 2005, and 1998. Currently, MVCA is working on developing regulatory floodplain mapping for the Fall River. This mapping will help both MVCA and its municipal partners better understand flood and erosion hazards, enabling the implementation of effective mitigation strategies to reduce the impacts of flooding within the Fall River watershed.

Fall River Floodplain Mapping Study Area

With the support and collaboration of Lanark County and Tay Valley Township, the Mississippi Valley Conservation Authority (MVCA) launched the Fall River Regulatory Floodplain Mapping project in the summer of 2024, with an anticipated completion date in the spring of 2026. This project will assess and map flood and erosion hazards along the Fall River in compliance with Section 28 of the Conservation Authorities Act, which governs the identification and mitigation of natural hazards. MVCA has secured funding from Natural Resources Canada (NRCan) through the Flood Hazard Identification and Mapping Program (FHIMP) to carry out this initiative.

The Fall River has not been mapped previously, leaving the risks of flooding and erosion in the area not well understood. The regulatory maps produced during this project will provide valuable insights for MVCA and its municipal partners, enabling the identification of flood and erosion risks and the development of mitigation strategies to reduce the impacts of flooding and fluvial erosion within the Fall River watershed. Additionally, these maps will inform MVCA’s capital infrastructure projects, as well as its flood forecasting and warning systems, and emergency management programs.

The Fall River will be modelled from its outlet from Sharbot lake to its confluence with the Mississippi River, downstream of Fallbrook, and regulatory floodplain mapping will be developed from the town of Maberly to the Mississippi River.

Next Steps

Floodplain mapping involves many components, including data collection, hydrological and hydraulic analyses, public consultations, and the development of floodplain and regulatory limit maps. As of March 2025, data collection and hydrological analyses are in progress. A consultant has been retained to carry out the hydraulic analysis and floodplain mapping, which is expected to be completed by the fall of 2025. Once finalized, the maps will be presented to MVCA’s Board of Directors for review and approval at the end of 2025.

A Public Open House is tentatively scheduled for Fall 2025. During this event, community members and stakeholders will have the opportunity to review the draft regulatory floodplain maps and engage in one-on-one discussions with MVCA staff about specific questions related to the floodplain, the mapping process, and its potential impacts. Local Indigenous communities are being actively consulted throughout the duration of the project.