Identify Flood Risks with the Toronto Flood Map

The Toronto Flood Map can help answer questions for Toronto residents, businesses, tenants, home-buyers, builders, insurance policy holders and insurance brokers / adjusters /actuaries interested in flood risk:

• Is a neighbourhood at risk of flooding during severe rain storms? Along what roads or portions of roads have property owners reported flooding during large rainfall events (July 8, 2013, August 19, 2005, May 12, 2000)?
• Is the area you are considering buying or renting in flood prone (so does the property of interest have flood risk mitigation measures in place, like a backflow valve to control sewer back-ups, or good lot drainage to keep runoff away from windows, doors and the foundation wall)?

Residents and businesses have reported flood incidents to the City of Toronto after extreme storm events. Calls are made during a flood event or afterward, sometimes as part of an insurance claim related to property damage. The City's map is is shown below.

City's map: Toronto Water Basement Flooding Location Map

As shown on the close up of the City's map below, only major roadways and points of reference are available, making it difficult to pinpoint a local area of interest. Unfortunately the City's map is not at a sufficient scale to show local streets with high historical flooding risk.

Close up of City's map (no local streets shown)

May 2000 locations estimated with symbol (!) on City's map

As a further limitation, May 2000 flood report locations are only shown with a symbol (!) as the original City map did not embed Geographic Information System fonts in the exported PDF file. These symbols are off-set from the reported basement flooding location (red dots in the legend).

Our Toronto Flood Map overcomes City map limitations and reveals high risk areas and neighbourhoods that have flooded during recent severe weather events.

Of course there are limitations in interpreting the flood location map:

• The City of Toronto is investing heavily in improvements to the sewer system to limit risks so some areas may no longer have the same risk after construction as they had in the past.

• Affected property owners may have invested in individual risk reduction measures (back-flow valves, sump pumps, improved lot grading, etc.) to protect their property from further damage.

• Not all flooding is reported so virtually any property along any street could experience flooding under certain conditions. For example, any property could experience flooding if the private sewer or drainage systems on the individual properties are not maintained (clogged foundation drains / weeping tiles, lateral service connection blocked with tree roots or other debris), or if there are other risk factors (reverse slope driveway, etc.).  This explains some isolated flood locations.

• Because the high intensity area of a storm may cover only part of the city, the density of flood locations reflects the relatively higher local rain stress on the drainage system, and not necessarily the local drainage system capacity compared to other parts of the city.  Other storms may affect parts of the City in a greater way (e.g., August 19, 2005 affected the north part of the City, while July 8, 2013 affected the west part).

• Individual addresses cannot be identified due to the scale of the map and spatial accuracy.

Nonetheless, Toronto Flood Map can still show the relatively higher flood risk streets within a neighbourhood.  Currently the map shows flood reports for the August 19, 2005 and May 12, 2000 storms. The May 12, 2000 basement flooding locations on the City's map have been corrected / adjusted so that affected streets can be identified.  The July 8, 2013 storm flood report locations, available through other City reports, will be available shortly as will other historical reports reported through local studies.