F12 Presentation
2020 Spring Freshet Update
Regular Meeting of Council May 11, 2020
Page 1 of 16 Presentation Outline
• Fraser Basin Overview • Snow Water Indices (2020) • Environment Canada Forecast • Fraser River Flow Rates and Water Levels • Delta’s Flood Plan • Status of Delta’s Flood Preparation
Page 2 of 16 Fraser Basin Overview
• Fraser Basin Watershed Area 2 – Basin Area - Fraser River 233,000 233,000 km km2 – Fraser Basin covers about 1/3 of the Province • Watershed Contributions – Upper Fraser - 44% – Thompson - 26% – Middle and Lower – 30% Harrison and • River Flood Flow Information Chilliwack – Spring Freshet typically Peaks in late Rivers 15% May or June – 1894 Flood Flow – 16,990m3/s – 1948 Flood Flow – 15,180 m3/s
Page 3 of 16 2020 Fraser Basin- May 1 Provincial Snow Water Index = 106%
Page 4 of 16 2018 Fraser Basin- May 1 Provincial Snow Water Index = 109%
Page 5 of 16 Fraser River Snowpack – May 1, 2020 Basin % of May Normal Basin % of May Normal (April Value) (April Value) Upper Fraser West 109 (136) North Thompson 118 (117)
Upper Fraser East 143 (147) South Thompson 124 (123)
Middle Fraser 91 (111) Nechako 86 (101)
• Snowpack levels in most regions of the Fraser Basin are above normal • Snowpack peaked in mid-April, low-to-mid elevation snowmelt finished. • Fraser Basin average snowpack is 106% as of May 1 ,2020, and 112% of normal for Fraser above Hope • An above-normal freshet can be expected according to the May 1, 2020 data • Flooding may occur if heavy rainfall takes place during freshet • Staff will continue to monitor the weather and flow forecasts
Page 6 of 16 Environment Canada Forecast
The long-term forecasts indicate about The long-term forecasts indicate a 50% probability of less precipitation than 40% to 60% probability of a warmer usual summer(until July) than usual summer (until July)
Page 7 of 16 Fraser River Flow at Hope
Page 8 of 16 Fraser River Peak Forecast 2020
Page 9 of 16 Daily Fraser River Flow Comparison For 2020 at Hope Gauge
Maximum Daily Minimum Daily Mean 2020 Discharge
16000
14000
12000
10000 /s) 3
8000 Discharge (m 6000
4000
2000
0 1-Jan 20-Feb 10-Apr 30-May 19-Jul 7-Sep 27-Oct 16-Dec Date
Page 10 of 16 Daily Level for 2020 Fraser River at Mission
Maximum Daily Minimum Daily Mean 2020 Level Stage 2 Level Stage 3 Level 7.5
6.5
5.5
4.5
3.5 level level (m)
2.5
1.5
0.5
1-Mar 21-Mar 10-Apr 30-Apr 20-May 9-Jun 29-Jun -0.5 Date
Page 11 of 16 Downstream Flow Sensitivity
Alex Fraser Bridge
Page 12 of 16 Delta’s Flood Plan
Stage 1 – Current Condition – Planning and Preparedness
Stage 2 – Reading of 6.0 metres on the Mission Gauge – Heightened Monitoring and Preparedness – Pre-Flooding Operational Activities
Page 13 of 16 Delta’s Flood Plan Stage 3 – Reading of 7.0 metres on Mission Gauge – Notify Public – Evacuate High Risk Areas Stage 4 – Flood Fighting – Road Closures – Rescue Services – Public Information Advisories Stage 5 – Recovery
Page 14 of 16 Status of Delta’s Flood Preparation
• Annual Dike Inspection – Complete • Sand Bag Supplies – Over 100,000 bags and 70 tonnes of Sechelt sand available • Concrete Lock-blocks – Approximately 200 blocks available • High Profile Highway Barriers – Approximately 100 barriers available • Rip Rap – Approximately 200 tonnes available
Page 15 of 16 Questions?
Fraser River 1948 Page 16 of 16