Changes

==Pluvial (Surface) flooding==  

==Pluvial (Surface) flooding==  

Pluvial flooding occurs when a heavier storm exceeds the urban drainage capacity and causes flooding in some low-lying areas. This results in traffic interruption, economic loss, and other issues. As the climate changes, the incidence of extreme weather events in Ontario is expected to increase and the urban drainage capacity may be overwhelmed more often.  

Pluvial flooding occurs when a heavier storm exceeds the urban drainage capacity and causes flooding in some low-lying areas. This results in traffic interruption, economic loss, and other issues. As the climate changes, the incidence of extreme weather events in Ontario is expected to increase and the urban drainage capacity may be overwhelmed more often.  

LID’s effects urban flooding at a scale of urban drainage systems

LID’s effects urban flooding at a scale of urban drainage systems Kim & Han  (2008);and  Han & Mun (2011) conducted studies to assess if the installation of a [[rainwater harvesting]] cisterns could help solve existing urban flooding problems without expanding the capacity of the existing urban drainage system.

Kim & Han  (2008);and  Han & Mun (2011) conducted studies to assess if the installation of a rainwater storage tank can help solve existing urban flooding problems without expanding the capacity of the existing urban drainage system.

==Riverine Flooding==

==Riverine Flooding==

Urbanization increases impervious surfaces and the increased impervious surface will result in an increase in runoff, as a result the flows exceed the capacity of the receiving downstream section of river and this may cause flooding.

Urbanization increases impervious surfaces and the increased impervious surface will result in an increase in runoff, as a result the flows exceed the capacity of the receiving downstream section of river and this may cause flooding.

''“Hydrological changes associated with urbanisation are increased storm runoff volumes and peak flows (Qp), faster flow velocities and shorter time of concentrations. A reduction in infiltration generally leads to less groundwater recharge and baseflow.The flashy response results in tremendous stresses for the urban stream and downstream receiving areas (Walsh et al., 2005)."''

''“Hydrological changes associated with urbanisation are increased storm runoff volumes and peak flows (Qp), faster flow velocities and shorter time of concentrations. A reduction in infiltration generally leads to less groundwater recharge and baseflow.The flashy response results in tremendous stresses for the urban stream and downstream receiving areas (Walsh et al., 2005)."''

*wet ponds;

*wet ponds;

*[[dry ponds]];

*[[dry ponds]];

*[[infiltration]] facilities with quantity control component; and,

*[[infiltration]] facilities and other low impact development practices with quantity control component.

*low impact development practices with quantity control component.

Infiltration facilities and low impact development practices (such as [[bioretention cells]] and [[rainwater harvesting]]) are typically designed to manage more frequent and lower magnitude rainfall events. However, should these practices be designed for year round functionality, with sufficient flood storage capacity, the volume reductions associated with these practices will only be recognized where the local municipality has endorsed the use of these practices and has considered long term operations and maintenance.

Infiltration facilities and low impact development practices (such as [[bioretention]] and [[rainwater harvesting]]) are typically designed to manage more frequent and lower magnitude rainfall events. However, should these practices be designed for year round functionality, with sufficient flood storage capacity, the volume reductions associated with these practices will be recognized where the local municipality has endorsed the use of these practices and has considered long term operations and maintenance.

==Background Research==

==Background research==

TRCA conducted [[modeling]] to evaluate different stormwater management measures (LID and Ponds) in mitigating impacts of development on the peak flow and runoff volume.  

TRCA conducted [[modeling]] to evaluate different stormwater management measures (LID and Ponds) in mitigating impacts of development on the peak flow and runoff volume.  

A sub-catchment in Humber River was selected that has an area of 35.71 ha.  

A sub-catchment in Humber River was selected that has an area of 35.71 ha. The existing land use in the sub-catchment is agriculture and the proposed future land use is employment land with 91% total imperviousness.

The existing land use in the sub-catchment is agriculture and the proposed future land use is employment land with 91% total imperviousness.

Hydrological model run were carried out by integrating different stormwater management measures (LID and SWM Pond) for 2-year and 100-year 6-hr AES design storms.

Hydrological model run were carried out by integrating different stormwater management measures (LID and SWM Pond) for 2-year and 100-year 6-hr AES design storms.

#Quality treatment provided using an oil/grit separator immediately upstream of each of the infiltration chambers, filtration through the infiltration chamber, and finally a stormwater management facility provided prior to discharging from the site.

#Quality treatment provided using an oil/grit separator immediately upstream of each of the infiltration chambers, filtration through the infiltration chamber, and finally a stormwater management facility provided prior to discharging from the site.

#Final erosion control provided within the stormwater management facility, controlling release rates to maintain the existing condition erosion exceedance values.

#Final erosion control provided within the stormwater management facility, controlling release rates to maintain the existing condition erosion exceedance values.

*Final design required both LIDs to reduce the overall runoff volumes, but also sub-surface storage chambers to provide quantity control for rare storm events up to the *100-year design storm. Due to large area required for truck parking, limited opportunities for more landscaping to promote evapotranspiration, runoff volumes increased beyond ability of LIDs to negate the need for quantity control.

#Final design required both LIDs to reduce the overall runoff volumes, but also sub-surface storage chambers to provide quantity control for rare storm events up to the 100-year design storm. Due to large area required for truck parking, limited opportunities for more landscaping to promote [[evapotranspiration]], runoff volumes increased beyond ability of LIDs to negate the need for quantity control.

<h3>Example 2. West Gormley, Town of Richmond Hill</h3>

<h3>Example 2. West Gormley, Town of Richmond Hill</h3>

'''Stormwater Management Strategy'''

'''Stormwater Management Strategy'''

*Use a combination of increased topsoil depths, perforated storm sewers, stormwater management facility, and an infiltration facility to provide quality, quantity, and reduce runoff volumes to match pre-development.

#Use a combination of increased topsoil depths, perforated storm sewers, stormwater management facility, and an infiltration facility to provide quality, quantity, and reduce runoff volumes to match pre-development.

*Even with favorable soils and maximum use of infiltration techniques, site still requires quantity control storage for large storm events.

#Even with favorable soils and maximum use of infiltration techniques, site still requires quantity control storage for large storm events.

<h3>Example 3: 3775-4005 Dundas St West (includes 2-6 Humber Hill Ave), Toronto</h3>

<h3>Example 3: 3775-4005 Dundas St West (includes 2-6 Humber Hill Ave), Toronto</h3>

*Water balance/Erosion Control – Retention of 5 mm event on-site

*Water balance/Erosion Control – Retention of 5 mm event on-site

==Stormwater Strategy==

'''Stormwater Strategy'''

Large portion of the roof proposed as green roof and cistern proposed in underground parking to capture remaining volume to meet 5 mm target.  Water to be used for irrigation and carwash stations.

#Large portion of the roof proposed as green roof and cistern proposed in underground parking to capture remaining volume to meet 5 mm target.  Water to be used for irrigation and carwash stations.

Quality target achieved as majority of site is ‘clean’ roof water or directed to pervious area. Underground storage tank provided to satisfy municipal release rates to receiving storm sewer system.

#Quality target achieved as majority of site is ‘clean’ roof water or directed to pervious area. Underground storage tank provided to satisfy municipal release rates to receiving storm sewer system.

#Final design required both LIDs to reduce the overall runoff volumes, but also sub-surface storage chambers to provide quantity control to meet municipal requirements.

Final design required both LIDs to reduce the overall runoff volumes, but also sub-surface storage chambers to provide quantity control to meet municipal requirements.

#Due to underground parking limited opportunities for infiltration LIDs but used green roof to promote evapotranspiration, and cistern to reduce runoff volumes.

Due to underground parking limited opportunities for infiltration LIDs but used green roof to promote evapotranspiration, and cistern to reduce runoff volumes.  

==Data Analysis/Modelling==

==Data Analysis/Modelling==

*Inlet design to accept the minor and major system

*Inlet design to accept the minor and major system

*How to incorporate emergency overflow structures into the design?

*How to incorporate emergency overflow structures into the design?

*What features can be incorporated to all you to adjust the infrastructure?

*What features can be incorporated to adjust the infrastructure?

Check for related content on [[Peak flow]]

Check for related content on [[Peak flow]]