Flood Forecasting Methods and Models Calgary, Alberta February 19, 2014

Transcription

1 Flood Forecasting Methods and Models Calgary, Alberta February 19, 2014

2

3 Why Am I Here?

4 Why Am I Here? It s Winter Olympics time! Colorado is the home of such athletes as Lindsey Vonn, Todd Lodwick, Mikaela Shiffrin, and 16 other athletes.

5 Why Am I Here? It s Winter Olympics time! Colorado is the home of such athletes as Lindsey Vonn, Todd Lodwick, Mikaela Shiffrin, and 16 other athletes. Colorado is in the same time zone as Alberta, so we were easy to get hold of.

6 Why Am I Here? It s Winter Olympics time! Colorado is the home of such athletes as Lindsey Vonn, Todd Lodwick, Mikaela Shiffrin, and 16 other athletes. Colorado is in the same time zone as Alberta, so we were easy to get hold of. Colorado and Alberta share similar topography, climate, western cultures, and demographics, and both had devastating regional floods of similar magnitude and similar results in the summer of We lost streamgauges too.

7

8 Colorado Average Annual Precipitation

9 Peak precipitation is always falling in Colorado Peak precipitation by season: Winter Mountains Spring Front Range/Urban Corridor Summer Eastern Plains Fall Western Regions Lower Elevations While peak flood season generally exists from mid-april to mid-october, precipitation is always falling somewhere.

10 Flood Threats in Colorado Generalized rain or rain-on-snow (generally late April to mid-june) Localized flash flooding by convective mechanisms (generally July and August in Eastern Colorado, Aug-Oct in western Colorado) Snowmelt (uncommon) Ice Jams (very uncommon) Post-Wildfire Flooding (increasingly common)

11 Big Thompson Canyon lives lost See Big Thompson: Profile of a Natural Disaster by David McComb

12 South Platte River Denver 1965 $3 billion

13 Rainfall Frequencies 7 Day

14 Quick Summary of Damages 10 fatalities (most in CO flood since 1976) 20 counties impacted 16,000+ damaged homes 1,882 destroyed homes 750 damaged businesses 200 destroyed businesses 200 miles of state highways damaged Very preliminary estimate of $2 billion

15 Fun City in Estes Park Photo from Twitter

16 Highway 34, East of Greeley Photo by Tom Browning

17 I-25 Big Thompson Flooding Photo from Twitter

18

19 Highway 7 Washout Photo by Estes Park News

20 Highway Washouts in Estes Park Photo from Twitter

21 Loveland Fairgrounds Photo from Twitter

22 Jamestown: the only way across to the other side of town for awhile.

23

24 Back side of house from previous photo. Occupant was killed by wall of water, rock and mud

25 Their former home site nothing left - Courtesy of Dave Rosenberg

26 Home in Evans

27

28 Key Mitigation/Preparedness Actions Aggressive floodplain management regulations Threat Detection Network and Forecasting Flood Warning Response Plans Emergency Manager Preparedness and Training Flood exercises with response agencies and public Public education what to do before, during, and after a flood

29 Requirements for Heavy Rain High amounts of moisture available Atmospheric method to process that moisture

30 Pre-flood 24-hr forecasts on September 11 were not consensus for major flooding but forecasts pointed out it would be a flash flood threat day. NSSL WRF model run Sept 10 for accumulated rain by Sept 12, 6AM. - Fcst 2-3in not the 6-9in observed. - Picked the right place. NWS meteorologists did not issue FF watch but did highlight local isolated strong storms. Issued FF Warning at 920PM on reports. CWCB FTB issued moderate-high threat of flash flooding for Sep Rain rates of 1.2in/hr for 2-6 hrs ( in) in thunderstorms/general rain UDFCD issued Message 1 s for nuisance street flooding until NWS issued FF Warning at 920PM.

31 Colorado Flood Threat Bulletin 11AM Flood Threat forecast map SEPT 10, 2013, 11AM SEPT 11, 2013, 11AM Low threat Moderate threat SEPT 12, AM SEPT 13, AM High threat

32 Colorado Flood Threat Outlook Issued Low threat Moderate threat High threat

33 Colorado Flood Threat Outlook Issued Low threat Moderate threat High threat

34 Two Parallel Groups in Operation Flood Task Force and Water Available Task Force (Technical Monitoring) Snowpack, Streamflows, Reservoir Levels, Soil Moisture Short, Medium, and Seasonal Climate Predictions Flood Technical Advisory Partnership (Policy Monitoring) Legislative and Policy Monitoring and Development Outreach needs

35 River Basin Forecast Centers Provide predictions for seasonal runoff Good for water supply and snowmelt runoff, not as useful for rain

36 Flood detection network equipment locations of rain gauges, stream gauges, and weather stations

37 Establish Monitor Stage and Flood Stage for Each Site Monitor Stage Flood Stage Decision Protocol Already Established For Each Level

38 Flood Warning Response Plan Establishes Decisions, Notifications, and Authorities

39 Notifications Residents need to be educated as to what actions to take Keep people out of their cars! Keep social media up to date

40 CoCoRahs Community Collaborative Rain, Hail, and Snow Network Excellent for storm documentation Radar ground truthing Significant weather reports go straight to NWS as a red flag, customizable

41 CoCoRahs Community Collaborative Rain, Hail, and Snow Network Hour Totals

42 Rainfall Totals Sept 9-16 Conversion: 17.8 inches = 450 mm

43 Reexamining Flood Hydrology Gridded 15-minute rainfall available from entire storm Reservoir storage and outflows available Peak flows in key locations known through stream gauges or forensic hydraulics Calibrate for both volumes and peak at known locations, then run design storm Policy Decision: How to handle stored flows in water supply reservoir

44 Boulder Creek Hydrology Evaluation

45 New Precipitation Frequency Atlas ont.html?bkmrk=co

46 Lessons Learned - Communication False information is abundant in a disaster Provide continual and consistent messages and information Leaders must aggressively address false information Both scheduled and ad-hoc communications are important Listen to your community you need to know what they know

47 Lessons Learned - Response Citizens are hungry for information Initially, it is better to be quick than 100% right Aggressively address false information Social media and internet are replacing television and radio Be prepared for excessive volume to crash internet sites; have a backup plan Do not forget about pets! Keep people out of their cars!

48 Lessons Learned Recovery Start collecting information as soon as possible You never know how or when you will need data more is better System redundancy and resiliency is critical Resist the urge to quickly build back the way things were or to roll back higher standards Use the flood as an opportunity for better resiliency

49 General Lessons Learned Always collect as much data as you can There is simply no replacement for open space The best time to make decisions is before the flood event, not during Beware of citizen complacency Pay attention to geomorphology Take advantage of water supply/flood relationships Don t take it personally floods can be mitigated, they are not prevented

50 Suggested Links Colorado Flood Decision Support System NWS Quantified Precipitation Forecasts, 1-7 Days (includes southern Canada) Flood Threat Bulletin 2013 Flood Information On decades-long development of open space

51 THANK YOU! For more information, contact: Kevin Houck Colorado Water Conservation Board , x3219 cwcb.state.co.us