June 23 rd 2017 Flood Event 27 June 2017 Dwight Boyd Director of Engineering
Presentation Outline Focus of this presentation is on West Montrose • Chronology of Event • Weather Warnings • Monitoring System Alerts • Watershed Response • Flood Warnings • Lessons Learned Next Steps • Questions
Weather Forecast and Warnings June 22 nd Weather Network Forecast Afternoon June 22 nd • Weather Network Forecast June 22 nd for June 23 rd Forecast rainfall for June 23 rd on the afternoon of Thursday June 22 nd 5-10 mm forecast for June 23 rd 2017. Environment Canada Weather Warning June 22 nd • Orangeville -Grand Valley - Southern Dufferin County Issued at 23:11 Thursday 22 June 2017 Conditions are favourable for the development of severe thunderstorms that may be capable of producing strong wind gusts, large hail and heavy rain. Severe thunderstorms are possible tonight. ### Large hail can damage property and cause injury. Strong wind gusts can toss loose objects, damage weak buildings, break branches off trees and overturn large vehicles. Remember, severe thunderstorms can produce tornadoes. Heavy downpours can cause flash floods and water pooling on roads. Severe thunderstorm watches are issued when atmospheric conditions are favourable for the development of thunderstorms that could produce one or more of the following: large hail, damaging winds, torrential rainfall. Please continue to monitor alerts and forecasts issued by Environment Canada. Kitchener - Cambridge - Region of Waterloo Issued at 21:24 Thursday 22 June 2017 Conditions are favourable for the development of severe thunderstorms that may be capable of producing strong wind gusts, large hail and heavy rain. Severe thunderstorms are possible tonight. ### Large hail can damage property and cause injury. Strong wind gusts can toss loose objects, damage weak buildings, break branches off trees and overturn large vehicles. Remember, severe thunderstorms can produce tornadoes. Heavy downpours can cause flash floods and water pooling on roads. Severe thunderstorm watches are issued when atmospheric conditions are favourable for the development of thunderstorms that could produce one or more of the following: large hail, damaging winds, torrential rainfall. Please continue to monitor alerts and forecasts issued by Environment Canada. .
Rainfall Early Morning June 23 rd 2017 Rainfall information has been compiled from a range of sources to document this event. These sources, include monitoring sites at GRCA dams, Maitland Valley CA monitoring sites, private land owners, CoCoRaHS and Environment Canada. As the attached map illustrates over a two day period total exceeding 100 mm and in some case 130 mm were exceeded. Some sites noted rain gauges overflowed therefore total may be under estimated by some observers. The majority of this rainfall occurred between 2 am and 6 am based on recording rain gauge data from Luther Dam, Woolwich Dam and Arthur. Also these rainfall totals were over a large area. CoCoRaHS – Community Collaborative Rain Hail and Snow Network https://cocorahs.org/
Rainfall Early Morning June 23 rd 2017 Twelve Hour Precipitation Totals June 22 nd 2017 8 pm to June 23 rd 2017 08:00 am Attached Weather Radar Image illustrates both the amount and extent of heavy precipitation over the northern third of the Grand River Watershed. The attached image is based on weather radar from Buffalo New York. Actual totals may be underestimated although they appear to agree and confirm ground observed rainfall totals. Voice alert of rainfall exceeded notified GRCA duty officer on call at 3:30 am, 25 mm of rainfall received in 24 hours. The senior dam operator on was contacted shortly after 3:30 am. He dispatched dam operators at 4:00 am. Director of Engineering who was the senior dam operator was contacted a 4:50 am and was work in the office by 5:40 am By 6 am the rainfall total was 120 mm.
Rainfall Early Morning June 23 rd 2017 Nexrad Radar
Rainfall Early Morning June 23 rd 2017 Voice alert of rainfall exceeded notified GRCA duty officer on call at 3:30 am, 25 mm of rainfall received in 24 hours. The senior operator on call was contacted shortly after 3:30 am. He dispatched dam operators at 4:00 am. Director of Engineering who was the senior operator coming on call was contacted a 4:50 am and was working in the office by 5:40 am By 6 am the rainfall total was 120 mm.
Inflow into and Discharge From Shand Dam The attached charts illustrates how quickly the river responded. Each grey square on the blue line indicates the hourly flow. The inflow at Shand Dam rose from around 5 m3/s at 1:00 am to 400 by 11:00 am. Reservoir storage was used to reduce and delay the downstream flood peak. Delaying the discharge from Shand Dam is intended to allow time for flow from the Irvine River downstream of Elora to Peak. On June 23 rd the Irvine River had a double peak that was not forecast or expected.
Inflow into and Discharge From Shand Dam Flow from the Irvine River Delaying the discharge from Shand Dam is intended to allow time for flow from the Irvine River downstream of Elora to Peak. On June 23 rd the Irvine River had a double peak that was not forecast or expected. The second peak from the Irvine River combined with the discharge from Shand Dam to increase flows higher than originally expected through West Montrose.
Inflow into and Discharge From Shand Dam Flow from the Irvine River Flow West Montrose Flows peaked through West Montrose at 500 m 3 /s. Highest since 1974 (674 m 3 /s, 1972 (634 m 3 /s)
History of Flooding at West Montrose The adjacent chart illustrates the maximum annual instantaneous flow at the West Montrose gauge by the covered bridge. The last time flows exceeded 500 m3/s was May 1974. West Montrose is also subject to ice jam flooding. Some previous ice jams floods may have exceeded levels similar to those experienced this past week. Several of the other events illustrated on this chart benefited regulation provided by Shand Dam. Historical Data Referenced from the Water Survey of Canada Records
Flooding in West Montrose June 23, 2017 Relative to Flood Thresholds The adjacent chart illustrates the flow hydrograph relative to flood thresholds through West Montrose. Flows from Carrol Creek to the West of West Montrose also contributed to flooding in West Montrose during this event.
Areas Draining to West Montrose The adjacent chart illustrates the flow hydrograph relative to flood thresholds through West Montrose. Flows from Carrol Creek to the West of West Montrose also contributed to flooding in West Montrose during this event. Areas downstream of Shand Dam accounted for about 40% of the peak flow through West Montrose separate from the area upstream of Shand Dam.
Flood Warnings and Communications During the Event June 23, 2017 06:17 am Contacted Dale Martin Flood Co-Ordinator for Woolwich Township asked him to arrange closure of Three Bridges Road indicated West Montrose campground would be flooded, Indicated GRCA would call camp ground directly to request removal of trailers on the flood flats below 180 m 3 /s. June 23, 2017 06:22 am Contacted West Montrose campground requested trailers be removed from the flood flats below 180 m 3 /s. Flood Message #1 June 23, 2017 09:00 am The trailer park in West Montrose will be flooded early this afternoon, the trailer park operator has been advised. Township staff are asked to monitoring conditions in the Village of West Montrose; it is expected that levels will peak later this evening through West Montrose . June 23, 2017 10:00 am Contacted Woolwich Township Flood Co-ordinator provided flood maps for West Montrose indicated 280 m3/s flood goes up to 4th line in West Montrose Trailer park. June 23, 2017 11:00 am Call from West Montrose Campground, informed them to move people out of lower area, effective flooding to 4th Street later today June 23, 2017 1:15 pm Contacted Woolwich Township Flood Co-ordinator expect West Montrose peak to reach 400 m3/s @ 6 pm. Requested Glasglow Street be closed. Flood Message #2 June 23, 2017 1:30 pm The trailer park and portions of the Village of West Montrose will be flooded Friday afternoon. Flood co-ordinators in Woolwich Township are asked to warn residents as necessary. This magnitude of flooding through West Montrose was last experienced in May 2000. June 23, 2017 16:50 pm Status requested by Woolwich Township Flood Co-ordinator forecast update for West Montrose and St. Jacobs, concern about flooding of the long facility in St. Jacobs, confirmed long term care facility in St. Jacobs would not be flooded. Updated forecast for West Montrose 460 m3/s. Flood Message #3 June 23, 2017 5:00pm The trailer park and portions of the Village of West Montrose flooded Friday afternoon and levels are expected to peak Friday evening. Flood co-ordinators in Woolwich Township have warned residents.
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