Slide 1

Learn about how you can be better prepared for flooding from industry professionals. Visit their booths for resources, advice and more!

Toronto and Region Conservation Authority 1

Slide 2

Flood Risk in the Dixie-Dundas Area

March 2, 2020

Presented by TRCA and the City of Mississauga

Slide 3

Presentation Outline• Understanding potential flooding in Mississauga

• How are flood risks managed

• Mississauga's mitigation projects

• What can you do now,

from the City's emergency management office

• TRCA's flood management resources

Toronto and Region Conservation Authority 3

The information contained in this presentation is copyright © Toronto and Region Conservation Authority

Slide 4

Toronto and Region Conservation Authority 4

Flooding has been a concern for residents of the Toronto area since the area was first settled. On October 15 and 16, 1954, Toronto received 210 mm of rain in a 12-hour period. For our region, Hurricane Hazel remains the most severe flood in recorded history. Recognizing the importance of flood management, the Provincial government amended the Conservation Authorities Act to enable an Authority to acquire lands for recreation and conservation purposes.

Slide 5

How are floodplain and flood risk maps made?

Toronto and Region Conservation Authority 5

Hypothetical Storms Models of real (and planned) land-cover Existing topography

This Photo by Unknown Author is licensed under CC BY-NC

How are flood maps made? TRCA must ensure that if development occurs in areas that are likely to experience flooding and erosion that it is properly permitted in order to decrease the risk of loss of life, personal injury and property damage. Building in a floodplain can have major consequences and can also affect neighboring properties by changing the physical characteristics of the valley or flood plain, or drainage to these properties. Developing flood plain maps requires detailed river and floodplain information and a lot of science and engineering. The maps are created based on canned scenarios to help engineers understand the worst-case scenario for development and planning purposes. Flood maps are not necessarily based on floods experienced in the past.

Slide 6

Flood Protection near Dixie-Dundas

Toronto and Region Conservation Authority 6

The Dixie-Dundas Channel and Dyke work together to provide flood protection to the City of Mississauga, specifically to the Dixie-Dundasneighbourhood, by reducing peak flows during flood events.

Slide 7

Toronto and Region Conservation Authority 7

The Dixie-Dundas cluster is subject to flooding due to a combination of capacity constraints in the river channel and backwater from multiple culvert crossings. Located on Little Etobicoke Creek, this cluster is near the intersection of Dixie Road and Dundas Street East in the city of Mississauga. It is a provincially designated Special Policy Area (SPA). The urbanized nature of the Little Etobicoke Creek watershed makes this cluster susceptible to flooding from intense summer thunderstorms. Significant flooding occurred during the July 8, 2013 storm when flows overtopped the engineered channel and began flowing south along Queen Frederica Drive.

Slide 8

8Toronto and Region Conservation Authority

Flooding can happen any time of year

Spring• Spring freshet –

accumulation of snow during the winter season can lead to flooding during the early spring, if conditions are right. When temperatures rise, snow melts and turns to runoff.

Winter• Ice jams – when a rise in

water level or a thaw in the ice breaks into large chunks, these chunks can become jammed at bridges or other obstructions. The rise will become backed up and can overflow its banks.

Fall• Seasonal weather systems

– large wet weather such as tropical storms, can last several days. Prolonged and heavy precipitation on top of already saturated soils causes rivers to rise.

Summer• Thunderstorms with

significant rainfall – within a short period of time, intense localized downpours from thunderstorms can produce flash flooding.

Slide 9

Cities & Conservation Authorities Work TogetherConservation Authorities

• Monitor watershed and weather conditions and operate a flood forecasting and warning system

• Issue Flood Messages• Operate Conservation Authority dams and flood control structures • Provide technical advice to municipalities • Maintain communications with municipalities and other agencies

Municipal Role

• Notify appropriate municipal officials, departments and agencies.

• Determine the appropriate response and deploy municipal resourcesto protect life and property.

• If required, declare a flood emergency and implement their emergency response plan.

• Request provincial assistance if neededToronto and Region Conservation Authority 9

Slide 10

Private drainage and surface waterContact your insurance representative for any property related damage due to flooding. Make sure your policy covers all types of flooding.

Residents near watercoursesProperties and structures located within a floodplain are especially susceptible to flooding due to the rise in water levels resulting from large, infrequent storm events.

Free Images fromhttps://pixabay.com/

Not all flooding comes from a river…

Sanitary sewer back up servicesMost backups occur when the sewer pipe that runs from your home to the Region’s main sanitary sewer pipe is blocked with items such as roots or grease. A blockage in the sewer pipe may cause wastewater to back up into your basement from the floor drain.

Catch Basin also known as a storm drain inlet or curb inlet at street level where storm water enters the catch basin.

Overland Flow/urban floodingHeavy downpour can cause storm drainage systems to overflow. Water may spill onto the property and enter the building through the basement windows or other openings.

Slide 11

Environmental ServicesGreg Frew, P.Eng.Acting Manager of Stormwater Projects & Approvals, Environmental Services

Slide 12

12

Types of flooding

© Todd Yates

© Reuters/Andy Clark

Riverine (fluvial) flooding occurs when water levels in a river rise and overflow its banks, spilling onto adjacent lands. Conservation Authorities identify riverine flood risks

Urban (pluvial) flooding occurs when a heavy rainfall event exceeds the capacity of the storm sewer system, causing the water to pond within the roadway. Urban storm infrastructure is the responsibility of municipalities.

Important Difference: Urban flooding can occur anywhere, independent of a water body

Slide 13

13

Storm sewers (minor system) – drain storm runoff from most everyday storms up to the 10-year storm (1 in 10 chance that it will occur in a given year).

Roadways (major system) – store and drain excess runoff when the storm sewer capacity is exceeded during major storm events.

Important: Temporary ponding is expected during these major storm events.

Urban Storm Drainage System

Slide 14

14

Looking for Solutions:City of Mississauga Flood

Studies

Slide 15

15

1. Dixie-Dundas Flood Mitigation Study

Flood spill from Little Etobicoke Creek

15

Objective: review options to reduce or eliminate the spill of riverine floodwaters from Little EtobicokeCreek near Dixie-Dundas

Timing: • Phase 1 Feasibility –2019/20• Phase 2 Municipal Environmental Assessment

Study – 2020/2021• Upcoming Open House #1- Late spring 2020

Slide 16

16

2. Little Etobicoke Creek Flood Evaluation Study

Underground stormwater storage galleries

16

Objective: review options to reduce the impacts of urban flooding in the Little Etobicoke Creek watershed

Timing: • Phase 1 Define flood risks – 2017/2018• Phase 2 Assessment of flood reduction

solutions – 2019/2020• Upcoming Open House #2 – late spring 2020

Storm sewer improvement works

Slide 17

Flood PreparednessBen Gallagher(A) Emergency Management SpecialistOffice of Emergency Management

Slide 18

Flood Preparedness There are actions you can take to reduce the risk of flooding, including:

• Wastewater back-up flooding• Install sanitary wastewater backflow preventer valve• Disconnect roof downspouts from wastewater lateral pipe

• Storm Sewer back-up flooding• Improve lot grading• Clean leaves and other debris from eaves troughs• Do not pour or flush items into drains or toilets that can cause blockages (grease, fats, oil,

wipes)

Some insurance companies offer overland flooding insurance. Contact your insurance broker to see whether this is available in your area.

Please visit the Office of Emergency Management table for more information on flooding preparedness and recovery

18

Slide 19

Insurance Tips

It is recommended to:• Have homeowners or tenants

insurance• Be familiar with your policy coverage• Know the 24/7 contact number to

start a claim• Inventory your belongings

19

Slide 20

General Emergency Preparedness Households are expected to be able to cope on their own for 72 hours (3 days) during emergencies.

You can prepare yourself and family by following the three steps to emergency preparedness:

1. Make a Plan2. Build a Kit3. Stay Informed

20

Slide 21

General Emergency Preparedness More information on emergency preparedness:

City of Mississaugahttp://www.mississauga.ca

Region of Peelhttps://www.peelregion.ca

Emergency Management Ontariohttps://www.ontario.ca/emo

Public Safety Canadahttps://www.getprepared.gc.ca

21

A digital handbook with information specific to Mississauga was created to help you understand and prepare for flooding: trca.ca/flood-risk-dixie-dundas

Slide 22

Toronto and Region Conservation Authority 22

Who to call during a flood?

• If you are in danger or there is a threat to life and safety, call 911 immediately.

• If you see any potential damage to your property, call your insurance representative as

soon as possible.

• For hydro-related questions, contact Alectra Customer Service at 1-877-963-6900

(Press 2).

• To report localized flooding on municipal roads, blocked catch basins or municipal

infrastructure, contact the City of Mississauga by dialing 3-1-1 (outside city limits: 905-

615-4311) or by emailing public.info@mississauga.ca.

• To report river flooding from the Etobicoke Creek, leave a voicemail on the TRCA floodline

at 416-661-6514. A flood duty officer will return your call.

Slide 23

Toronto and Region Conservation Authority 23

Sign up for Flood Messages

For important Mississauga updates, follow @CityMississauga

Slide 24

Site specific response planning

24

TRCA and the City of Mississauga work together on emergency planning, and the information we have from our modelling is used to inform contingency plans

Toronto and Region Conservation Authority

Slide 25

Continued Flood Monitoring

Nearby Stream & rain gauges

Stream Gauge:

• HY098 - Little Etobicoke

Precipitation Gauge:

• HY099 – Rathwood

TRCA has a network of real-time river and rain gauges across the GTA to:

• Monitor the water levels in specific stream and behind dams • Measure how much precipitation has fallen

beta.trcagauging.ca

Slide 26

Thank you

Toronto and Region Conservation Authority 26

Information presented today can be accessed online at:

trca.ca/flood-risk-flood-dixie-dundas

@TRCA_Flood

www.trca.ca/flood