2011 SPRING FRESHET UPDATE

May 19, 2011

Presentation Outline

1. Background — Fraser Basin— Snow Water Indices (2007, 2010, 2011)

2. Fraser River Flows and Water Levels3. Delta’s Flood Plan4. Status of Flood Preparation

1. Background• Fraser Basin

– Basin Area - Fraser River 233,000 km2

– United Kingdom 243,000 km2 – Fraser Basin is covers about 1/3 of

the Province

• Snow Indices – Snow Pack throughout the

province and converted to a Snow Water Index

2007 Snow Water Index

2010 Snow Water Index

2011 Snow Water Index (April 1)

2011 Snow Water Index (May 1)

Spuzzum Creek

Green Mountain

Snow Basin Indices – May 1

• Snow packs in Lower and Middle Fraser are well above normal, while Upper Fraser is slightly above.

• Overall, less snow levels than in 2007 and 1999.• Above normal freshet runoff can be expected in the Lower

Fraser, leading to a modest increase in flood risk potential.

Basin % of Normal Basin % of NormalUpper Fraser 109% Kootenay 142%

Nechako 109% Okanagan-Kettle 145%

Middle Fraser 122% Similkameen 141%

Lower Fraser 150% South Coast 157%

North Thompson 103% Vancouver Island 167%

South Thompson 110% Peace 103%

Nicola 151% Skeena Nass 110%

Columbia 111%

2. Fraser River Flows and Water Levels

• River Flood Flow Information– Spring Freshet typically peaks in late May or

June – Typical Freshet Flow approx. 8 - 10,000 m3/s– 1894 Flood Flow – 17,000 m3/s – 1948 Flood Flow – 15,180 m3/s– Niagara Falls – 2,800 m3/s only about one

fourth of the Fraser River peak flow

Largest basin in BC ~233,000 km2

44%

25%16%

Harrison and Chilliwack Rivers

15%

Percent Contribution of Annual Runoff at Mission

Hope

Mission

Flow at Fraser River Hope Gauge

River Flow May 9-May 16, 2011

River Flow Feb, 2009- May, 2011

Flow Update for 2011 - Current Flow slightly more than 6,100 m3/s- Predicted Freshet Peak approx. 10,000 to 11,000 m3/s (likely close to 6m at Mission) - Freshet timing likely in the next 2 to 4 weeks (Peak flow and Timing depends on temperature & precipitation)- Delta water levels are primarily tidal - Highest tides June 17-18, 2011 (1.5m freeboard on dikes)

Current Fraser River Flows and Predictions Fraser River at Mission

Water Level at Fraser River Mission Gauge

3. Delta’s Flood Plan• Stage 1 – Current Condition

– Planning and Preparedness• Stage 2 – Reading of 6.0 metres on Mission Gauge

– Heightened Monitoring and Preparedness– More Frequent Dike Inspections

• Stage 3 – Reading of 7.0 metres on Mission Gauge – Notify Public– Evacuate High Risk Areas

• Stage 4 – Flooding or Dike Failure– Road Closures– Rescue Services– Public Information Advisories

• Stage 5 – Recovery

4. Status of Delta’s Flood Preparation

• Annual Dike Inspection – underway• Sand Bag Supplies – Over 140,000 bags stored at

the Engineering Operations Works Yard• No-post barriers – Approximately 400 concrete

barriers in stock and available for use • Monitoring Provincial Updates (predicted river

level data after 5m at Mission)• Maintain watch for Erosion during peak flows

QUESTIONS?