217 217 217

200 200 200

255 255 255

0 0 0

163 163 163

131 132 122

239 65 53

110 135 120

112 92 56

62 102 130

102 56 48

130 120 111

237 237 237

80 119 27

252 174 .59

83 36

118

1

Angela M. Duren, P.E., P.H. USACE Portland District Senior Hydrologist 2017 Oregon Dam Safety and Reservoir Resilience Conference 28 February 2017

WILLAMETTE BASIN DAM SAFETY HYDROLOGIC STUDIES

Pasayten Wildnerness, WA Photo by Jeff Kish

OUTLINE

Dam Safety in the Corps Willamette Goals Hydrologic Assessment Approach for Dam

Safety in the Corps Brief Basin Background Site-Specific PMP Technical Approach Site-Specific PMF Technical Approach Hydrologic Loading Technical Approach Other Basin Hydrologic Studies

USACE DAM SAFETY RISK ASSESSMENT PROGRAM

USACE has over 700 Dams 2005 ASCE Infrastructure Report Card = F USACE Response = Risk Management

Center (Official in 2009) USBR Risk Assessment Approach to Assess Dam Risk

and Prioritizing Dam Remediation

As of 2015, Over 350 Dams have Undergone at Least 1 Round of Risk Assessment (Many have Undergone Multiple Rounds)

High Priority: Unsafe or Potentially Unsafe Failure initiation foreseen or very high risk

Failure Modes: Overtopping of the Dam Due to Rapid and Extreme Inflow Seismic Tainter Gates (Trunnion Friction)

Cougar Lookout Point

Hills Creek Fall Creek Blue River

Foster Green Peter

7 WILLAMETTE DAMS ARE OF NATIONAL CONCERN

GOALS 1. Develop Robust Hydrology to Support Dam Safety

Risk Assessment 2. Advance Hydrologic/Meteorologic Science and

Software

HYDROLOGIC STUDIES REQUIRED FOR DAM SAFETY RISK ASSESSMENT

Probable Maximum Precipitation (PMP), Probable Maximum Flood (PMF)

PMF is usually the Inflow Design Flood (IDF) Determines Adequacy of Spillway (ER 1110-8-2(FR))

Hydrologic Loading Curve (Pool Stage, Uncertainty vs Probability)

650

655

660

665

670

675

680

685

690

695

700

0

50,000

100,000

150,000

200,000

250,000

0 6 12 18 24 30 36 42 48 54 60 66 72

Elevation (ft, N

AV

D88)

Flo

w (c

fs)

Time (hrs)

Inflow

Outflow

Elevation

Stochastic

Deterministic

Site-Specific PMP/PMF Preliminary analysis shows overtopping at

some dams – do site-specific precipitation and runoff studies change that?

Pool Stage Frequency Curves How probable is the pool elevation of the

PMF and large events we haven’t seen before?

BACKGROUND Over 11,000 square miles

13 Headwater Dams to the mainstem Willamette River; 7 Dams in IES Phase II: Green Peter, Foster, Blue River, Cougar, Fall Creek,

Lookout Point, Hills Creek

Headwater drainage areas range from ~100-500 square miles

Valley (200 ft El.); Coastal Range (1,000-4,000 ft El.);Cascade Range (7,500-10,500 ft El.)

Willamette River – South to North, trib to Columbia River; meets near Portland

Several small consequence centers; larger cities near the main stem Willamette

BACKGROUND Headwater NAP: ~55-90 inches per year (depending on

basin)

SWE Ranges from 5” to 40” in Winter; 0” to 50” in Spring

EXTREME STORMS Pattern changes due to difference in temperatures between Equatorial and Polar regions

Average Position of Pacific High January (Ahrens, 2005)

Average Position of Pacific High July (Ahrens, 2005)

Rain Season: Nov-Mar but can go through to May; time of most of annual precipitation

Spring Season: Snowmelt source of inflow, May-June

Summer Season: Very little rain, June-August

0

2

4

6

8

10

12

14

16

0

10

20

30

40

50

60

70

80

Precipitation (inches)

Tem

pera

ture

(deg

rees

Fah

renh

eit)

Willamette Basin PMP with Uncertainty

Collect 10-20 Historical Storm Data (depths,

locations, trajectories, temperature)

Estimate the orographic areas of influence

Depth-area-duration curve development for

each storm

Storm transposition and maximization

Multiple PMP spatial and temporal patterns

with temperature sequences

SITE-SPECIFIC PMP TECHNICAL APPROACH

Extreme Storms Report

Uncertainty in SST, Maximization Carried Through

to PMP Computations = Upper, Average, Lower PMP

estimate

EXTREME STORMS REPORT

10

100

1000

10000

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Area

(sq

mi)

Precipitation Depth (inches)

1996 February Nehalem, OR

2006 November Nehalem, OR

1983 January Nehalem, OR

2007 December Haskins Dam, OR

2007 December June Lake, WA

1997 March June Lake, WA

1982 February Lone Pine, WA

2012 January Port Orford, OR

1996 November Port Orford, OR

2008 December Brookings, OR

2014 December Brookings, OR

Notes

(1) Location identifed by color of line (Red= Northern OR Coast, Black = Cascades, and Cyan = Southern OR Coast).

(2) Storm type identified by line type (Solid = Subtropical, and Dash = Mid-latitude).

72-hours

Goal: Collect and Synthesize Data to Support PMP Development

Analysis Conducted: Observed DAD Curves, Mass Curves

Isopluvials for all durations (1-96 hr)

Synthesis of data and reports for complete meteorologic understanding and description

EXTREME STORMS REPORT Key Storm Date Peak Gage Station

Maximum Precipitation Depth (in)

Average Willamette River Basin Precipitation Depth

(in)**

1 Day 3 Day 1 Day 3 Day

1 Feb 6-8, 1996 June Lake WA US 11.2 24.5 3.3 (3.0)

7.2 (7.0) Nehalem NE OR US 6.8 17.7

2 Mar 18-20, 1997 Paradise WA US 9.8 17.7 0.7

(0.4) 1.0

(0.9)

3 Nov 5-7, 2006 June Lake WA US 14.6 24.4 2.8

(2.0) 4.9

(5.4) Nehalem 9 NE OR US 11.8 22.4

4 Dec 2-4, 2007 Haskins Dam OR US 8.7 13.4 1.9

(1.9) 3.8

(4.0) June Lake WA US 8.1 16.1

5 Jan 18-20, 2012 Port Orford 5 E OR US 11.5 18.6 2.6

(3.1) 5.6

(5.8)

6 Feb 13-15, 1982 Lone Pine WA US 7.0 19.3 1.8

(2.0) 3.4

(3.2) Nehalem 9 NE OR US 6.0 11.0

7 Nov 17-19, 1996 Port Orford 5 E OR US 11.6 16.4 4.2

(4.0) 6.6

(5.9)

8 Dec 28-30, 2008 Brookings 4.2 ENE OR US 7.2 15.6 1.1

(1.3) 2.1

(3.3)

9 Dec 19-21, 2014 Brookings 4.2 ENE OR US 9.2 14.0 1.7

(2.6) 3.1

(3.8)

10 Jan 4-6, 1983 North Fork OR US 6.4 13.9 1.9 (1.5)

3.5 (3.5) Nehalem 9 NE OR US 4.7 13.0

** The value given is based upon on the average value measured at the NCDC precipitation gages located within the basin. The value in parentheses is based upon the average basin value from the daily PRISM data (PRISM, 2016).

10 storms selected based on runoff

Data collected for each storm event: HYSPLIT air parcel trajectories

Daily weather maps

PRISM daily and monthly precipitation and temperature data

Sea Surface Temperature data from NCAR, NOAA ESRL, IRICS

NRFC Historical flood information

Integrated water vapor from ESRL

Meteorologic description

Historical reports and articles

Vertical/Horizontal Transposition and Maximization: Based On SST, Transposition Location (Governs Barrier Elevation)Provide Lower, Average, and Upper Results by Carrying Uncertainties in SST and Sensitivity to Transposition Location All the Way through PMP Calculation = Lower, Upper, Best Estimate PMP vs Duration

SITE-SPECIFIC PMP: EXTREME STORMS AND UNCERTAINTY

Willamette Basin-wide PMF

HMS+ResSim Consequences

HMS+ResSim+RAS

Willamette Basin-Wide Wind/Wave Study

Willamette Basin-Wide Site-Specific PMP

Willamette Basin-Wide Coupled Hydrologic +

Reservoir Routing Model)

Spatial/temporal pattern sensitivity (4 spatial

patterns + 10 temporal events)

PMF TECHNICAL APPROACH

CALIBRATION AND VALIDATION

Goals and Constraints: Leverage PMF routing models to facilitate loading curve model development to extent possible Downstream flow is significant and coincident downstream hydrographs required for consequences and affect operations Learn what matters and what doesn’t for parameter sensitivity Calibration: 4 Winter, 4 Spring + 1964 Event Validation: 2 Winter, 2 Spring Unit hydrograph comparisons with historical design floods

CALIBRATION AND VALIDATION Some Challenges:

Availability hourly flow, precipitation, temperature data; Solutions include: PRISM disaggregation, HEC-GageInterp, adjustment factors, Cos method for temperature

Flow gage quality; Solution was using gage data rating system (1-5, 99)

Variability of performance based on calibration metric and among events; Solution was using performance ratings along with statistical metric (VG, G, S, US)

Synthesize large amount of results to understand variability of parameters; Solution was using pseudo tornado plots of results per sub-region of the larger Willamette Basin.

Validation difficult with wide-range of parameters for each calibration event; Solution was using 4 step process

Technical Approach: HMS, ResSim Calibration/ValidationHEC-WAT to

Integrate and Finalize

103 Subbasins

Lumped parameter (to leverage for loading curve models)

Snowmelt modeling

CALIBRATION AND VALIDATION METRICS AND GAGE RATINGS PER EVENT

Aggregated by major region of the Willamette River basin

Includes all winter and spring events Lower limit as average of minimum values

and upper limit as average of maximum values

‘Mod Range’ reflects when an outlier is removed that skewed the range

0.00 0.05 0.10 0.15 0.20

Middle Fork Willamette

Coast Fork Willamette

McKenzie

Long Tom

South Santiam

North Santiam

Middle Willamette

Lower Willamette (West)

Lower Willamette (East)

All

Hydraulic Conductivity (in/hr)

Mod Range

Full Range

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Middle Fork Willamette

Coast Fork Willamette

McKenzie

Long Tom

South Santiam

North Santiam

Middle Willamette

Lower Willamette (West)

Lower Willamette (East)

All

Baseflow Ratio to Peak

Mod Range

Full Range

CALIBRATION AND VALIDATION PARAMETERS

Dam Year Built

Unit Hydrograph

Source Duration (hrs) Flood Event Basis

Peaking Factor

Hill Creek 1961 DM1 6 1942-43 150% Lookout Point 1954 WCM 6 1942-43 150%

Fall Creek 1966 WCM 6 1964 150% Dorena 1949 n.a. n.a. n.a. n.a.

Cottage Groove 1942 Excel File Unknown 1942-43 Unknown Fern Ridge 1941 n.a. n.a. n.a. n.a.

Cougar 1964 DM2 6 1942-43 150% Blue River 1964 DM2 3 1964 150%

Green Peter 1968 DM2 6 1964 150% Foster 1968 DM2 6 1964 150% Detroit 1953 DM1 6 1942-43 150%

Comparison of calibration UHs with spillway design UHs (unpeaked)

General design approach: Derivation using observed flood hydrographs (1942-43 or 1964 flood) peaking (50%), 6-hour duration.

General agreement in shape

Match varies between max, min, avg UH with design UH (unpeaked)

0

2000

4000

6000

8000

10000

12000

14000

0 10 20 30 40 50 60 70 80

Disc

harg

e (c

fs)

Time (hr)

DM_NormalCalibrated (Average)Calibrated (Maximum)Calibrated (Minimum)

0

5000

10000

15000

20000

25000

0 10 20 30 40 50 60 70 80

Disc

harg

e (c

fs)

Time (hr)

DM_NormalCalibrated (Average)Calibrated (Maximum)Calibrated (Minimum)

0

1000

2000

3000

4000

5000

6000

7000

8000

0 10 20 30 40 50 60 70 80

Disc

harg

e (c

fs)

Time (hr)

DM_NormalCalibrated (Average)Calibrated (Maximum)Calibrated (Minimum)

Fall Creek

Lookout Point Hills Creek

CALIBRATION AND VALIDATION UNIT HYDROGRAPHS

Willamette Dams

Hydrologic Loading-

Major Subbasin Modeling

Provides Dam-Specific Loading

Curves

Regional precipitation frequency curve for each major

watershed

Unit hydrograph sampling for each major watershed

MCMC for HMS and WAT Code Development

Soil loss, baseflow sampling for each major watershed

Starting elevation sampling

Debris loading for each major watershed-(USBR Study)

Gate Failure Scenarios

Top 5-10 synthetic temporal and spatial pattern sampling

Critical precipitation duration analysis

SWE distribution analysis

WAT Validation Using USGS Volume Frequency Curve

HYDROLOGIC LOADING TECHNICAL APPROACH

Pool Stage Frequency Curve with Confidence

Limits

Hydraulics: Floodplain

Analysis, Dam Failure

Consequences: Loss of Life and Economics

Geotechnical: Seepage Failure

Geology: Seismic Failure (normal operations up to

gross pool)

Pool Duration Curves and Overtopping Depth

Final Integrated

Risk Analysis: DAMRAE

ALL Failure Mode Event Nodes

Risk = Probability of Load x Probability of Failure (Given the Load) x Consequences (Given the Failure)

Pool Stage Frequency

Example F-N plot

Hydrologic Loading Curve (Pool Stage, Uncertainty vs Probability) Reflects the response of a reservoir and the

associated uncertainties with the antecedent and event routing conditions.

Used with hydraulic and consequence modeling to estimate the damage and life loss for various possible failure modes of a dam.

Must be extended to peak elevations not yet experienced in the reservoir, such as the peak pool elevation generated by the PMF event.

HYDROLOGIC LOADING CURVE (POOL STAGE, UNCERTAINTY VS PROBABILITY)

Some Factors that Affect the Peak Pool for Any Given Event Temperature Precipitation intensity Spatial/temporal distribution of precipitation Antecedent snowpack Antecedent pool elevations Operations Baseflow Soil infiltration capacity Rainfall-runoff transformation (unit hydrograph)

HYDROLOGIC LOADING CURVE (POOL STAGE, UNCERTAINTY VS PROBABILITY)

OTHER ON-GOING HYDROLOGIC STUDIES….

Bayesian Hierarchical Modeling Regional Precipitation Frequency Analysis

Reconnaissance-Level Paleo-Flood Studies

USGS Columbia River Basin Regional Volume Skew Study

WRF Modeling Recreating Historic Storms; Maximization

INTERAGENCY PARTNERS USGS University of California at Davis USACE Engineering and Research Development Center (ERDC) USACE Hydrologic Engineering Center (HEC USACE Risk Management Center (RMC) West Consultants

ADVANCING METHODS AND DATA Incorporation of Bayesian Statistics in Risk Assessment Framework – Markov Chain

Monte Carlo (MCMC) Atmospheric Modeling; Dynamical Downscaling Improvements in Stochastic Sampling Processes, Computation Time, Storage, Post-

Processing Snowmelt Modeling Body of Knowledge and Methodology Empirical Database of Hydrologic Parameters in the Willamette Basin

LARGER COMMUNITY USGS Regional Volume Skew Study Storm Reanalysis Data Optimality of Historical Storms Critical Reexamination of HMR PMP Assumptions Empirical Hydrologic Parameter Distributions

Publicly Available, Free Software (HEC) Data Reviewed, POR flow data at critical locations in the watershed Hourly precipitation and temperature grids over entire Willamette Regional skew relationships Ability to develop empirical distributions of parameters such as soil loss, baseflow, unit hydrographs

HEC-WAT Ability to quantify uncertainty: Precipitation (depth, spatial/temporal), temperature, SWE, reservoir pool elevation,

unit hydrograph Tc, R, baseflow, soil loss HEC-HMS Ability to quantify uncertainty and incorporate into uncertainty analyses Multi-parameter optimization: Matrix of correlated parameters

DESIRED STUDIES…. NOAA Atlas 14 – Regional Precipitation Frequency