Model Development to Support Assessment of Flood Risk for the Columbia River Treaty Review

Transcription

1 Model Development to Support Assessment of Flood Risk for the Columbia River Treaty Review 2012 AWRA Washington State Conference Sara Marxen, P.E. U.S. Army Corps of Engineers Seattle District September, 2012

2 Presentation Outline I. Modeling Goals and Approach II. Data Collected III. Data Developed IV. Models built V. Use in the Treaty Studies Slide 2

3 The Columbia River System Mica Keenleyside Duncan Libby Originates in Canada, Canada has 15% of the basin area, 30% of average annual flow is from Canada, 50% of worst Columbia flood flows (1894) came from Canada. Flows 1,200 miles through 4 U.S. States, drainage area of 259,000 square miles Over 60 large dams and reservoirs owned and operated by many different entities Slide 3

4 Flood Risk Management Task: Evaluate Flood Risk Under Current and Future Operating Scenarios EM : Requires Risk Analysis Expected Annual Damage Annual Exceedance Probability Long Term Risk Conditional Non-Exceedance Residual Risk Goal: Provide Information to Support a Decision on Future of the Treaty Slide 4

5 Modeling Goals Implement Flood Risk Management Models should be flexible, maintainable, adaptable Accurate geospatial economic data Integrate hydrologic/reservoir/river/economic Increase automation in the approach Slide 5

6 What are we modeling? There are 1,000 of dams in the basin Really only 8 of them have specific operations that are regularly used and manageable Historically there are 22 reservoirs that are modeled as part of System Flood Risk Management More than 60 dams are modeled for hydropower Slide 6

7 Data Collected 1. LIDAR 1600 river miles, 3000 square miles 2. Use of existing and collection of new river crosssections/bathymetry 3. 3-D levee centerlines 4. structure inventory Slide 7

8 1. Hydrology 2000 level modified flows dataset Synthetic Low Probability Events Climate Change 2. Standardized run-off volume forecasts 3. Levee fragility Data Developed Slide 8

9 1. HEC-Ras 2. HEC-ResSim 3. HEC-FIA 4. HEC-WAT with FRA Models Developed Slide 9

10 Hydraulic Modeling Grand Coulee Albeni Falls The Dalles U S U S U S U S U S U S Dworshak Libby U S Hungry Horse McNary Slide 10

11 CRT System HEC-ResSim Model 67 projects in the model 36 with storage that can affect flood operations 8 which operate for the system Slide 11

12 CRT System HEC-ResSim Model Simulates reservoir operations at a planning level on a daily time-step. Reservoirs were initially chosen for inclusion based primarily on volume, and whether they were included hydropower or flood studies. Does not model ecosystem function (biop) operations Simulates the majority of CRT Flood and Hydropower operations Includes - flow routing, automated refill, continuous or refill based mode Slide 12

13 CRT System HEC-ResSim Model Approach to developing post-2024 operations. What will effective use and called upon look like? How can they be designed to provide the same level of flood risk but meet the treaty description? What does that mean for other users of the system? Slide 13

14 HEC-WAT Structure HEC-WAT Hydrologic Data HEC-ResSim Plug-In HEC-RAS Plug-In HEC-FIA Plug-In 2000 Modified HMS Flows/ Model Synthetic Events HEC-ResSim Model HEC-RAS Model Flow HEC-FIA Model WAT Simulation With Default Program Order Hydrographs Damages Hydrographs Hydrographs Simulation.dss Slide 14

15 Flood Risk System Inflow Q i Inflow Q i Time Time Q i Q b Reservoir 1 Reservoir 2 Outflow Q o Q o Inflow Q i Time Time. Slide 15

16 HEC-WAT Structure - FRA HEC-WAT with FRA option Forecast Sampler Fragility Sampler Breach Hydrographs Spreading Model Depths, Velocities per Grid Frequency Freq Sampler Hydrograph Sets Mean Forecast HEC- ResSim Unregulated Hydrographs HEC-RAS Model Regulated Hydrographs Simulation.dss Damage Sets RAS Mapper Depth Grids Damages HEC-FIA Model Model Convergence? Yes Net Benefit Sampler Benefits CSRA Expected Net Benefit, CDF No Slide 16

17 Flood Risk System Inflow Q i Inflow Q i Time Time Q i Q b Reservoir 1 Stage (ft) Probability of Levee Failure L i Outflow Q o Q o Reservoir 2 Inflow Q i Time. Time Reservoir Elevation Time Forecast Volume Observed Volume Slide 17

18 What does this mean for the Flood Risk Analysis Rather than this.. Year x has a peak of 435,000 cfs at The Dalles with no Called Upon Slide 18

19 What does this mean for Flood Risk Analysis Peak Flow Example: Each color represents a single year and the effect of forecast uncertainty on the resulting peak flow Forecast Volume Slide 19

20 Uncertainties Incorporated in FRA (short-term) Forecast uncertainty Starting reservoir pool elevation Stage/flow rating curves Roughness coefficients Levee breaching parameters/fragility Slide 20

21 Uncertainties Incorporated in FRA (long-term) HEC-ResSim Starting Storage/Elevation Stream routing coefficients Stage/flow Rating Curves Reservoir physical data: storage/elevation, release capacity, etc. Demands (water, power) Current Power Capacity (outages) Sedimentation changes Roughness Coefficients Bridge Debris Ice thickness Dam/levee breeching parameters Foundation Height Structure value Content Value Car Value Other Value Depth/Damage functions Population at Risk HEC-RAS HEC-FIA Weir Coefficients Gate Coefficients Bridge/culvert coefficients Contraction/Expansion coefficients Boundary Conditions (normal depth slope, etc.) Terrain Data Ground Elevation Slide 21

22 Many Other Uncertainties What will be an agreed upon called upon operation? What will be an agreed upon effective use operation? What could a CanadianTreaty Terminates operation look like? What Treaty operation will be agreed upon vs. what we assume? What biological operations will be desirable in U.S. and Canada? How will the basin change over time (people, places, demands)? How will the climate change over time? How will an operation change in real-time implementation, is it significant?. Slide 22

23 Example of using FRA to address Arrow Elevation: 70 Yr this Arrow Elevations: 70 Yr. Avg. Avg. Outflow (kcfs) Elevation (ft.) Apply probability to the operations cases based on expert knowledge. Incorporate that into flood risk /1/ /15/ /29/ /12/ /26/ /10/ /24/2010 1/7/2011 1/21/2011 2/4/2011 2/18/2011 3/4/2011 3/18/ Oct OCT NOV DEC JAN FEB MAR APR I APR II MAY JUNE JULY AUG I AUG II SEP Case 1 50% chance of occurring Case 4FB 25% chance of occurring Case 4C 20% chance of occurring Case NCS 5% chance of occurring 4/1/2011 Case 1 Case 2: 165 Case 2: 225 Case 3 Case 4 Case 1 (BCH) Case 4b Case 4C Case (Recom.) 7 Case 10 Case 14 Case 8 Case 9 Case 3b Case 15 Case 4FB (Alt. Case Arrow) 4c Avg Case 4q (17 yrs) Case 4FB 4/15/2011 4/29/2011 5/13/2011 5/27/2011 6/10/2011 6/24/2011 7/8/2011 7/22/2011 8/5/2011 8/19/2011 9/2/2011 9/16/2011 9/30/2011 Slide 23

24 What does this mean for the Treaty Studies We now have a tool in which operational changes in Canada or the U.S. can, relatively quickly, be evaluated for flood risk. This is only one piece of the puzzle that will be use to make a decision. Multiple studies through STT/SRT are ongoing: How should called upon and effective use work operationally? What is the impact of a less conservative flood risk operation? What is the impact of trying to meet more normative flow levels in the mainstem? What is the impact of more normative reservoir levels? Can levees be improved o reduce flood risk? Can levees be removed to reduce flood risk? What is an appropriate system-based dry year operation? Slide 24

25 Questions Acknowledgement goes to multiple engineers in Seattle, Portland, Walla Walla, Division Columbia Basin Water Management, Hydrologic Engineering Center, BPA and West Consultants Pete Dickerson, Ryan Cahill, Ron Malmgren, Geoffrey Walters, Kristian Mickelson,Tracy Schwarz, Jeremy Giovando, Travis Ball, Margaret McGill, Joan Klipsch, Matt Fleming, Chris Nygaard, and more! Slide 25