SEFM Case Study

Altus Dam, OK

Workshop on Probabilistic Flood Hazard Assessment

January 29 – 31, 2013
Acknowledgements

• Study funded by Bureau of Reclamation Dam Safety 

Office

• Report authors: Nicole Novembre, Victoria 

Sankovich, Jason Caldwell, and Jeffrey Niehaus

• Modeling guidance and assistance provided by: 

Mel Schaefer and Bruce Barker of MGS Consultants

• Technical check and peer review provided by: 

Joseph Wright, Robert McGovern, Robert Swain, 

and John England
SEFM Case Study: Altus Dam

Topics:

1. Project background

2. Calibration

3. Production runs

4. Results

5. Comparison to EMA

2820 mi2 total drainage area
Elevation

(3670 to 1480 ft)

Drainage Basin Elevation
Non-contributing Area
SEFM Case Study: Altus Dam

Topics:

1. Project background

2. Calibration

3. Production runs

4. Results

5. Comparison to EMA
2. Calibration

GOAL – estimate fixed parameters to be used in 

production runs.

Calibration parameters:

1. Soil infiltration parameters

2. Surface runoff parameters

3. Interflow parameters

4. Basin routing travel times

PROCESS – Select model parameters that produce 

results that most closely match observed flows.
Inputs for Calibration Runs

a) Hydrologic Runoff Units (HRUs)

b) HEC-1 Template

c) Meteorological Inputs

d) Hydrological Inputs
a) Hydrologic Runoff Units (HRUs)

Overlay:

• Precipitation zones (3)

• Soil zones (7)

• Elevation zones (1)

• Sub-basins (9)

64 HRUs

Precipitation 

Zones

Soil 

Zones

HRUs
b) HEC-1 Template

SEFM calculates runoff 

from each sub-basin.

HEC-1 defines connectivity 

and routing between the 

basins.
c) Meteorological Inputs

• Storm templates for each calibration storm

• Antecedent precipitation 

• Evapotranspiration
d) Hydrologic Inputs

Streamflow observations for each calibration event

Provide range of parameters for calibration:

• Soil infiltration parameters 

• Surface runoff unit hydrograph parameters

• Interflow unit hydrograph parameters
Soil Infiltration Parameters

(Schaefer and Barker, 2004)
Surface runoff unit hydrograph

(Schaefer and Barker, 2004)
Interflow Parameters

(Schaefer and Barker, 2004)
Calibration Process 

Generalized Likelihood Uncertainty Estimation (GLUE) 

method (Beven and Binley, 1992)

Compare model results to observed flows to determine 

best input parameters for the model:

• Calculate goodness-of-fit 

measures

• Calculate % error for Qp and V

• Visually compare hydrograph 

shapes
Calibration Process 

Perform a frequency run and compare frequency curves 

from model to frequency curves from streamflow data.

• peak flows

• 24-hr mean flows

• 72-hr mean flows 
SEFM Case Study: Altus Dam

Topics:

1. Project background

2. Calibration

3. Production runs

4. Results

5. Comparison to EMA
3. Inputs for Production Runs

a) Hydrologic Runoff Units (HRUs) – same as calibration

b) HEC-1 Template – same as calibration

c) Meteorological Inputs

d) Hydrological Inputs
c) Meteorological Inputs

• Storm duration

• Storm volume (precipitation magnitude frequency)

• Storm templates (spatial and temporal distribution)

• Storm seasonality

• Antecedent precipitation

• Evapotranspiration
d) Hydrologic Inputs

• Antecedent soil moisture

• Soil moisture at start of climatic year

• Antecedent streamflow

• Initial reservoir elevation

• Calibrated values:

– Soil infiltration parameters

– Surface runoff unit hydrograph parameters 

– Interflow unit hydrograph parameters 
Production Runs

• Specify the number of runs 

• Specify the plotting position

• Run SEFM:

– SEFM selects a month of storm occurrence

– A storm template is selected and scaled 

– Parameters are selected based upon month

– HEC-1 input files generated for each simulation
Production Runs

• Run HEC-1 batch file

• Import HEC-1 output files into SEFM

• Events are ranked to develop frequency curves
SEFM Case Study: Altus Dam

Topics:

1. Project background

2. Calibration

3. Production runs

4. Results

5. Comparison to EMA
Peak Discharge frequency curves

Red – 95th percentile precipitation

Blue – 50th percentile precipitation

Orange – 5th percentile precipitation
15-day volume frequency curves

Red – 95th percentile precipitation

Blue – 50th percentile precipitation

Orange – 5th percentile precipitation
10,000-yr Hydrographs based on 

Peak Discharge
10,000-yr Hydrographs based on 

Volume
Reservoir elevation frequency curves

Red – 95th percentile precipitation

Blue – 50th percentile precipitation

Orange – 5th percentile precipitation
SEFM Case Study: Altus Dam

Topics:

1. Project background

2. Calibration

3. Production runs

4. Results

5. Comparisons to EMA
Comparison to EMA with paleoflood 

data
Thank You

Questions?