Flooding is Canada’s most costly natural hazard, resulting in over $2 billion in insured catastrophic loss every year. Floods can happen in any season, whether from heavy rain, rapid snowmelt, ice jams, coastal storm surges, or strong onshore winds.
Floodplain maps are one of the tools that planners use to guide decisions about how property may be used. They are created to help protect property and improve safety by indicating where flooding may occur, predicting the path of floodwaters based on natural land features and man-made infrastructure such as roads and buildings that divert the flow of water.
There are several types of flooding. Riverine flooding occurs when the water levels of rivers rise, overflowing their banks. Otonabee Conservation studies and maps this type of flooding and regulates development within and adjacent to floodplains. Shoreline flooding occurs when critical high-water levels and waves result in shoreline flooding and/or erosion. Finally urban flooding consists of street flooding, basement flooding, and flooding of other low-lying areas due to the overflow of local drainage systems. Municipalities are responsible for managing this type of flooding.
Given the increase in frequent and severe dramatic weather events, there has been a concerted effort to anticipate their impact on developed areas where the protection of property and people is most critical. Mapping identifies properties and infrastructure that are at risk of flooding during severe storms. The identification of high risk areas helps guide responsible land use and development decisions. Accurate mapping can also expedite planning applications by reducing the need for some studies, and helps identify flood reduction opportunities. Surprisingly, these efforts to identify areas at risk are not universally cheered.
Otonabee Conservation has been developing updated local floodplain maps in our area. In 2022, they released a Floodplain map of the Baxter Creek Water-shed. This body of water originates near the northern edge of the Ganaraska Forest, flowing northward from the Oak Ridges Moraine and eventually draining into the Otonabee River south of Whitfield Landing. The study area for Baxter Creek extends from the Otonabee River along the main branch and through the Village of Millbrook. It includes49 km of tributary routes which have an upstream drainage area of 125+ Ha, including the head-water areas of the Oak Ridges Moraine.
Properties located within floodplain boundaries require Otonabee Conservation approval for building permits. Updated mapping potentially extends the area requiring Conservation Authority approval. Property owners can see their property on a floodplain map by submitting their address into the floodplain mapping portal atwww.otonabeeconservation.com/permits-planning/floodplain-mapping/. Finding a property on a floodplain map allows its owners to understand where they can safely build early in the planning process without paying for a survey.
Floodplains sometimes encompass areas that have already been developed, including historical communities that were traditionally established close to waterways. Historic buildings located within floodplains are usually given a kind of grandfather treatment by their host municipalities. These areas are designated as Special Policy Areas (SPAs) and each have their own specific requirements. Historic properties within these zones are subject to restricted development/redevelopment activity, and often offer greater flexibility than typical floodplain regulations. Each one is subject to approval by the Minister of Municipal Affairs and Natural Resources. The SPA is a compromise zoning tool that supports the viability of historic locations while acknowledging site-specific flood risks. This designation balances flood risk management goals with the economic viability of historic communities.
Downtown Millbrook falls within an SPA. The details of the area and restrictions are out-lined in the Official Plan, that include building features, mini-mum ground floor elevations, and requirements for building material composition that can withstand anticipated hydrostatic forces stemming from a flood. New residential structures or redeveloped structures within this zone are subject to minimum elevation, safe access and safe parking criteria. Some types of development are specifically prohibited, including nursing and seniors housing, and group homes for the physically or men-tally challenged and hospitals. Facilities where chemical, hazardous or toxic chemicals are not allowed in this area, as well as new development supporting emergency services including police, fire and ambulance services and electrical substations that could be jeopardized by a flood are also not permitted within an SPA.
Given the growing costs of flooding across the country, insurance companies are beginning to take note and price their property insurance policies accordingly. In Montreal, updated floodplain maps issued last fall have triggered some lenders to restrict mortgage lending to properties in these areas. Some of the residents whose property were impacted pushed back against the updated maps, understanding their potential financial implication on their property values. The floodplain maps didn’t create the risk, they just identified and explained it. Understanding the risk is the starting point to develop measures to reduce its impact.
Better understanding flood risks can help municipalities manage their potential liabilities and prepare for emergencies, and help homeowners understand and mitigate the flood risks to their properties.