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Line 20: + + + − TRCA undertook modeling excises to evaluate effectiveness of 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. The existing land use in the sub-catchment is agriculture and the proposed future land use is employment land with 91% total imperviousness. + + − + + + + + + − + − Finally, LID as standalone cannot control post-development peak flows to pre-development peak flows under major storm events. + − Therefore, in order to meet flood control requirements, LID need to be augmented by some flood storage measures such as dry/park ponds, underground storage. + +
→Background Research
==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.
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.
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.
Scenarios evaluated include:
Scenarios evaluated include:
#LID measures that provide 25 mm on-site retention
#LID measures that provide 25 mm on-site retention
#SWM pond to control post-development peak flows to pre-development peak flows.
#SWM pond to control post-development peak flows to pre-development peak flows.
#Combination of scenario 1 and scenario 2
#Combination of scenario 1 and scenario 2
Runoff volume and peak flow reductions were calculated.
Runoff volume and peak flow reductions were calculated.
===Peak Flow===
===Peak Flow===
25 mm on-site retention using LID measures can reduce post-development peak flows generated from 2 to 5 year design storms by over 26%, whereas for 50 and 100 year design storms it reduces only 4% and 1% respectively. This shows that LID will not reduce significantly the post-development peak flows generated from major storms.
*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.
This shows that LID will not reduce significantly the post-development peak flows generated from major storms.
In order to meet flood control requirements, LID need to be augmented by some flood storage measures such as dry/park ponds, underground storage.
===Runoff Volume===
===Runoff Volume===
25 mm on-site retention using LID measures can reduce post-development runoff volume generated from 2 to 5 year design storms by over 52 %, whereas for 50 and 100 year design storms it reduces only 33% and 30% respectively. This shows that the post-development runoff volume generated from major storms going to receiving features can be reduced considerably by implementing LID to retain 25 mm.
*The 25 mm on-site retention using LID measures can reduce post-development runoff volume generated from 2 to 5 year design storms by over 52 %,
*For 50 and 100 year design storms it reduces only 33% and 30% respectively.
This shows that the post-development runoff volume generated from major storms going to receiving features can be reduced considerably by implementing LID to retain 25 mm.
==Literature Review==
==Literature Review==