City of Toronto Overland Flow Map - 100-Year Storm Major Drainage System Spread & TRCA Watershed Major Drainage Centreline

CityFloodMap.Com presented GIS-based, hydrologic and hydraulic overland flow analysis over the past couple years (the "2015" Toronto overland flow analysis and spatial analysis correlating overland flood limits to reported basement flooding in 2000,2005 and 2013, and then the "2016" southern Ontario-wide analysis that includes refined hydrologic parameters). This provides an important insight into urban flood risk management and the influence of surface flooding on sanitary/wastewater system inflows (e.g,. via doors, windows, walk-outs, depressed driveways) - the extraneous flows that particularly stress partially separated sanitary systems, causes sewer surcharge and basement sewage back-up.

Here is the analysis clipped to the City of Toronto including the estimated 100 year flow spread and a 2x 100-year flow spread. The also includes overland flow paths within Toronto (the centreline of the major drainage flow path) and outside of Toronto covering the entire TRCA watershed areas ((c) CityFloodMap.Com):

The major drainage system flow spread in Toronto is essentially a buffer from this centreline considering each reaches hydrology (rational method) and hydraulics (standard road cross section assumed, but overland flow segment defines longitudinal average slope (or a minimum to avoid zero's for segments across filled sinks that have no slope). As a bonus, geotagged social media is embedded in the ArcGIS Online map - generally this is useless using the search term 'flood' to filter images but there is the odd correlation of overland flow path with real flooding pictures. The map is interactive - you can zoom in and even search for an address - enjoy! Hopefully the social media Flickr and Twitter images become more relevant and abundant over time. If you want to see a clean version without social media, scroll to the bottom of the page. More details on the analysis including the basement flooding correlation is described here:


Urban Flood Risk from Flood Plains to Floor Drains from Robert Muir

An example geotagged surface flooding picture that corresponds to the mapped overland flow path:


The map below is cleaner, excluding social media geotagged 'flood' images, and showing only City of Toronto 100-year overland flow spread and flow path centreline in TRCA watersheds ((c) CityFloodMap.Com). Note, approximate TRCA regulation boundaries are estimated from camaps.ca georeferenced image feature, and shoreline/slope regulation areas have been excluded to focus more on where river flood risks exist:

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