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Home My WebLink AboutExecutive #05/18 Review of August 7, 2018 Storm Event 10-08-2018Review of August 7, 2018 Storm Event Toronto and Region Conservation Authority August 10, 2018 Executive Committee Presented by: Dan Hipple, P.Eng. Senior Manager, Water Resources Engineering Chief Flood Duty Officer August 10, 2018 Toronto and Region Conservation Authority Overview • Prior to August 7t" Storm Event • August 7t" Storm Event • Post Event Observations • Moving Forward Toronto and Region Conservation Authority I 2 Prior to August 7t" Storm Event Morning assessment indicated maximum potential of 19mm of rainfall for the day Call into Ontario Storm Prediction Centre (DSPC) indicated very low possibility of isolated showers/thunderstorms, with rainfall amounts of 10mm or less. 6:45pm — Phone call to OSPC again, where they advised of a small rainfall cell over Highway 404 and Steeles Avenue area OSPC discussion focused on potential event for following day (August 8t"), and advised to call back the following morning Continued to monitor as normal. Toronto and Region Conservation Authority 3 August 7t" Storm Event g 8:45pm — First low level alarm for Black Creek at Highway 401 gauge was received, showing very sudden increase in water levels. - Rainfall gauges surrounding stream gauge showed little to no precipitation; felt it may have been interference in stream (branch, etc.). ® Rainfall noted in Mississauga, but decided to wait to confirm. ® 9:00 — 9:30pm — Black Creek at 401 continued to rise, Black Creek at Alliance began to increase, and staff discussed options and action plan. - Radar showed rainfall over Black Creek. Call to OSPC at 9:25pm indicated "slow moving tropical rainstorm" formed with possible rainfall amounts of 20-75mm, and EC was just releasing a Special Weather Statement for Toronto, Mississauga and Brampton during phone conversation. Toronto and Region Conservation Authority 4 August 7t" Storm Event 9:55pm — Began drafting Flood Watch Message, and contacting City of Toronto. Call went to Toronto Central Dispatch, warning of high water levels in the Jane/Wilson area, and that Alliance/Rockcliffe area increasing. Dispatch was made aware that the Alliance area is prone to basement flooding, but Dispatch did not provide any recommendations. Staff tried contacting 311, but call couldn't get through and connection was lost. 10:00 — 10:30pm — Black Creek at Alliance gauge peaked just under the High -High Alarm. Flood waters rose 3.5m in 1.5 hours, but precipitation gauges still showing little response; Flood Message draft was approved and began issuing; Further call to 311 was unsuccessful. Toronto and Region Conservation Authority 5 August 7t" Storm Event Showing Water Level for BLACK CR AT HWY 401 (HY005) f ram 2018-08-07 at 7:00 PM to 2018.08-07 at 11:55 PM 11! In E — 134 XA-WL�]23COOm) � 133 132 121 3YA1 qugl 2018 1032 10LlD 'SCi2 2151] 2Y 2290 223-0 195ave to dashboard Showing Water Level for BLACK CREEK AT ALLIANCE (HY097) from 2018-08-07 at 7:00 PM to 2018-08-07 at 11:55 PM 103 HA-WL)1D2]Wn) u-w�U2>-2v2m1 E — 103 q l01 i Toronto and Region Conservation Authority I 6 August 7t" Storm Event By 11:05pm, Flood Watch Message posted to TRCA website, twitter page, and text messaged to municipal partners. Issues with mail distribution program delayed email release to 11:20pm. Internal Situation Report distributed by 11:05pm. Further calls to partners, including Brickworks, Toronto Dispatch, and GO Transit Control. Follow-up return calls to those who left messages on the Flood Line. Staff continued to monitor events and coordinate with partners into the night. Black Creek at Alliance gauge was receding, with peak suggesting that the banks were not overtopped at the gauge location. Toronto and Region Conservation Authority 7 Post Event Observations Reports on preliminary rainfall amounts were being sent out: Environment Canada (EC) issued a statement at 3:43am confirming that 50-75mm of rainfall fell very in a localized are in Toronto from North York to the Island over 2-3 hours; EC's Billy Bishop Airport gauge showed 72mm; and News outlets and social media reporting amounts higher than 100mm from unknown/unconfirmed sources. TRCA rain gauges: Underwhelming, with —20mm at the nearest gauge and 1.4mm at Pioneer Village, and Omm in Mississauga; All decision making and reactions were based on stream gauges and information from OSPC/EC. Further radar imagery showed storm formed and hit in area of no rain gauges. Toronto and Region Conservation Authority 8 Post Event Observations tJewrnarket utxa Burkeetw, I omllo Station Moan GWIM BallunITM G—da'uw NowRu'Gra G GIM Maim Schomberg y .. GardwMl mffhlle I_r. 0 Orengeullle � King EitY y Nabhla� 010 rx2 Courtici Whithy Oshawa RlbhmOYSd Hill� � _ Munn acai Markham Ajax canedws u Vault tering 1.i 6 M1rMMYWI 0 y Oa'rFl TM'! mptan Maann H.11s ce3laGExcW,N Taremo Allla Mississauga / xnrr.F Hinck Mdlnn Toronto and Region Conservation Authority 9 Post Event Observations Toronto and Region Conservation Authority 110 Post Event Observations Toronto and Region Conservation Authority 111 Post Event Observations Composite Reflectivity 17 10:OOpm Tuesday August 7th, 2018 ILI :1r 4. nearby TRCA real4ime rain gauge �J Toronto and Region Conservation Authority 12 Post Event Observations Toronto and Region Conservation Authority 13 �dford- Wear Gasilllmbury NowmerNet H att t eth Vabri AW_ _ Is Mono W — HY060 HY083 HY011 - J • J • HY002 HY069 � HYOa3 ■ mese wll w .. Hvo]o •a b r� •Hv04a o •HY009 � HV021 HY085 vaue • l HY102 111"OA" HY050 r HV088a 02] H O6]. o33 • 7 .,a to Jr HY008 rF v 0 5 0 20 Rainfall Accumulation Gauge ID Qlexame r -_ - p_!. --'wAj*== Gau eID Gauge Name HYW2 Albion Hills 1Y 1 Ialdlaw8usoepot HY067 West Humber at Hwy] 11:20am 07/08/2018-11:20am 08/08/2018 HYWB Brickworks HY013 Me Rotaileat 16th WM York Pumping Station HY00B Brpd[Wert laMfill IM4sl Mloe Dam HY071 York Re'on Works Yard HYDII BNas Mill CA HYM Mssonap Works Yard HY083 Dak Ridges HV021 0ufferin Reservoir HY050 Wolin ide Works Yard HYCa6 RL Clark W Tommo arM flegion N 1Y 7 GRon Dam HYO55 Restomlon Semlon HYf@8 Pioneer Vill e ,40 Conservation A HMI Heaft lake CA H X-0 Stovffville Mm HY099 Rathwood AuHr°rltY W= Pettlmrt Works Yard Toronto and Region Conservation Authority 13 Post Event Observations Wednesday, August Stn Hydrometrics staff visited the Alliance Avenue, Rockcliffe Boulevard and Hillside Drive area, looking for signs of high water; In the area of the TRCA gauge, the Black Creek did not overtop its banks, as indicated in our gauge information. Noted debris in several locations indicating areas where Black Creek overtopped its banks downstream of TRCA gauge location. Due to our gauge location and information, this was not known on the evening of August 7th Toronto and Region Conservation Authority 14 Post Event Observations — 501 Rockcliffe Boulevard, rear driveway adjacent to Black Creek Toronto and Region Conservation Authority 15 Moving Forward Re-evaluate Black Creek Overtop Criteria Investigate if adjustments required to High -High Alarm associated with Black Creek at Alliance gauge; Investigate potential for rain gauge in area; Discuss with City of Toronto staff on protocols related to future flooding in area. Toronto and Region Conservation Authority 16 Questions? Dan Hippie, P.Eng. Phone: 416 661 6600 x 5336 Email: dhipple@trca.on.ca TRCA website: www.trca.on.ca TRCA Gauging website: beta.trcagauging.ca www.trca.ca Toronto and Region Conservation Authority