Changes

Flood mitigation strategies that incorporate Low Impact Development (LID), traditional stormwater management, and hybrid infrastructure can manage stormwater effectively and reduce flood impacts.

Flood mitigation strategies that incorporate Low Impact Development (LID), traditional stormwater management, and hybrid infrastructure can manage stormwater effectively and reduce flood impacts.

==Types of flooding==

==Types of flooding==

! Pluvial (surface) flooding

! Pluvial (surface) flooding

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[[File:Reflecting-on-the-devastating-2013-storm-mississauga-takes-lead-in-municipal-flood-resilience-the-pointer-be39ea9b.jpg|300px|thumb|right|Street flooding in Mississauga (The Pointer, 2023)<ref>The Pointer. 2013. Reflecting on the devastating 2013 storm, Mississauga takes lead in municipal flood resilience. https://thepointer.com/article/2023-07-30/reflecting-on-the-devastating-2013-storm-mississauga-takes-lead-in-municipal-flood-resilience</ref>.]]

[[File:Reflecting-on-the-devastating-2013-storm-mississauga-takes-lead-in-municipal-flood-resilience-the-pointer-be39ea9b.jpg|400px|frameless|center]] Street flooding in Mississauga (The Pointer, 2023)<ref>The Pointer. 2013. Reflecting on the devastating 2013 storm, Mississauga takes lead in municipal flood resilience. https://thepointer.com/article/2023-07-30/reflecting-on-the-devastating-2013-storm-mississauga-takes-lead-in-municipal-flood-resilience</ref>.

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* Caused by intense rainfall that exceeds soil infiltration and storm sewer capacity, especially in urban areas with impervious surfaces.

* Caused by intense rainfall that exceeds soil infiltration and storm sewer capacity, especially in urban areas with impervious surfaces.

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! Fluvial (riverine) flooding

! Fluvial (riverine) flooding

| [[File:Screenshot 2025-09-22 100405.png|300px|thumb|right|Don River floods DVP (City News, 2024)<ref>City News. 2024. From the scene: Don Valley River floods section of DVP, stranding drivers. https://www.youtube.com/watch?v=fbyaYZy0d0A&t=68s</ref>]]

| [[File:Screenshot 2025-09-22 100405.png|400px|frameless|center]]Don River floods DVP (City News, 2024)<ref>City News. 2024. From the scene: Don Valley River floods section of DVP, stranding drivers. https://www.youtube.com/watch?v=fbyaYZy0d0A&t=68s</ref>.

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* Occurs when rivers exceed their capacity due to heavy rain or snowmelt, resulting in water overtopping the banks and flowing into adjacent areas.

* Occurs when rivers exceed their capacity due to heavy rain or snowmelt, resulting in water overtopping the banks and flowing into adjacent areas.

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! Coastal (shoreline) flooding

! Coastal (shoreline) flooding

|[[File:Screenshot 2025-09-19 115121.png|300px|thumb|right|Lake Ontario floods Toronto Island (Toronto Life, 2017)<ref>Toronto Life. 2017. Flooding on the Toronto Islands is terrible—but also weirdly beautiful. https://torontolife.com/life/flooding-toronto-islands-terrible-also-weirdly-beautiful/</ref>]]

|[[File:Screenshot 2025-09-19 115121.png|400px|frameless|center]]Lake Ontario floods Toronto Island (Toronto Life, 2017)<ref>Toronto Life. 2017. Flooding on the Toronto Islands is terrible—but also weirdly beautiful. https://torontolife.com/life/flooding-toronto-islands-terrible-also-weirdly-beautiful/</ref>.

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* Driven by storm surges and lake-level rise due to storm surges or seiches.   

* Driven by storm surges and lake-level rise due to storm surges or seiches.   

==Modelling Flood Mitigation Potential of Conventional LIDs==

==Modelling Flood Mitigation Potential of Conventional LIDs==

TRCA conducted [[modeling]] to evaluate the capacity of different stormwater management measures (LID and Ponds) to mitigate impacts of development on the peak flow and runoff volume. A sub-catchment in Humber River was selected that has an area of 35.7 ha. The existing land use in the sub-catchment is agriculture and the proposed future land use is employment land with 91% total imperviousness.

TRCA conducted [[modeling]] to evaluate the capacity of different stormwater management measures (LID and Ponds) to mitigate impacts of development on the peak flow and runoff volume. A sub-catchment in Humber River was selected that has an area of 35.7 ha. The existing land use in the sub-catchment is agriculture and the proposed future land use is employment land with 91% total imperviousness.

===Peak Flow===

===Peak Flow===

*The 25 mm on-site retention using LID measures reduced post-development peak flows generated from 2 to 5 year design storms by over 26%,

*The 25 mm on-site retention using LID measures reduced post-development peak flows generated from 2 to 5 year design storms by over 26%,

*For 50  and 100 year design storms it reduces only 4%  and 1% respectively.  

*For 50  and 100 year design storms it reduces only 4%  and 1% respectively.  

# Smart blue roof systems can regulate rooftop runoff by storing and controlling the release of rainwater

# Smart blue roof systems can regulate rooftop runoff by storing and controlling the release of rainwater

# In addition to peak flow control, blue roof systems can facilitate runoff reduction through rainwater reuse and evaporative rooftop cooling

# In addition to peak flow control, blue roof systems can facilitate runoff reduction through rainwater reuse and evaporative rooftop cooling

===Example 5: [https://sustainabletechnologies.ca/app/uploads/2020/09/CVC-Glendale-Rain-Garden-Case-Study.pdf Glendale Public School Rain Garden]===

===Example 5: [https://sustainabletechnologies.ca/app/uploads/2020/09/CVC-Glendale-Rain-Garden-Case-Study.pdf Glendale Public School Rain Garden]===