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Floodplains Reimagined Hydrodynamic Modeling Calibration

February 2023

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What is Hydrodynamic Model Calibration?

  • What are Hydrodynamic Models
    • computer program that simulates the conveyance of water across the landscape – rivers, floodplains, rice fields etc. 
    • Computations based on laws of physics and typically driven (boundary conditions) by historic measurements or estimated flows (gages)
  • Model Calibration
    • Tuning of model parameters to ensure model results are an accurate representation of reality
    • Accomplished by simulating historic conditions and comparing model output (flow, water level) to measurements made at gages

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Objectives

  • Presentation objectives
    • Provide calibration status of Butte Basin and Colusa Basin models
    • Demonstrate baseline field level management performance
  • Background
    • Butte Basin and Colusa Basin modeling approach and technical methodologies based on a foundation of work developed for the Sutter Bypass Management Plan
    • Sutter Bypass model
      • Model previously calibrated, validated, and applied to baseline and two scenarios with a suite of similar actions
      • Model will be used in conjunction with Butte Basin simulations

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Modeling Uncertainties

Why Models are wrong

  • Simplified physics, such as 1D and 2D representations, to facilitate simulations of large areas
  • Lack of boundary condition data (flows and water levels)
  • Lack of topographic data (e.g. inundated areas during LiDAR collection)
  • Lack of calibration data
  • Lack of information on small scale hydraulic structures and their operations

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“All models are wrong, but some are useful”. George E. P. Box, British statistician

Why Models are still useful

  • Models can be calibrated to minimize systematic bias, such that errors are randomly distributed
  • Uncertainty can be quantified statistically and used to determine a models’ range of applicability

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The Butte and Colusa models are best suited for RELATIVE COMPARISONS of scenarios to the baseline. Because the uncertainty is similar for each model simulation, the relative differences in results can be attributed to the differing scenarios instead of to model uncertainty

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Hydrodynamic Model Calibration Overview

Mainstem Sacramento River Calibration

  • Main Channel and Overflows
  • 1997, 1998, 2006, 2019 water years

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Butte Basin Calibration

  • 2019 water year

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Colusa Basin Calibration

  • 2019 water year
  • Field management

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Model Areas

1D Cross Sections

Colusa

Basin

Butte

Basin

Sutter Bypass

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Hydrodynamic Modeling

Mainstem Sacramento River Calibration

  • Main channel
  • 1997, 1998, 2006, 2019 water years
  • 1D representation of mainstem

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Model Areas

1D Cross Sections

Colusa

Basin

Butte

Basin

Sutter Bypass

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Sacramento River - 1998 Medium Flood Event 4/8/1998 - 5/20/1998

Ord Ferry

Butte City

Colusa

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Sacramento River - 2006 Flood Event

Ord Ferry

Butte City

Colusa

Colusa Weir

Moulton Weir

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Sacramento River - 1997 Flood Event

Ord Ferry

Butte City

Colusa

Colusa Weir

Moulton Weir

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2019 Water Year

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Sacramento River - Longitudinal Profile MAX Stage WY 2019

Ord Ferry

Butte City

Colusa

Colusa Weir

Moulton Weir

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Sacramento River - Longitudinal Profile Stage 2/14/2019 03:00

Ord Ferry

Butte City

Colusa

Colusa Weir

Moulton Weir

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Sacramento River - Longitudinal Profile 3/24/2019 00:00

Ord Ferry

Butte City

Colusa

Colusa Weir

Moulton Weir

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Hydrodynamic Modeling

Butte Basin Calibration

  • 2019 water year
  • Overflows via Mouton and Colusa Weirs
  • Interior calibration (Butte Creek) is still underway

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Model Areas

1D Cross Sections

Colusa

Basin

Butte

Basin

Sutter Bypass

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Butte Basin - Moulton Weir Spill, WY 2019

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Butte Basin - Colusa Weir Spill, WY 2019

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Hydrodynamic Modeling

Colusa Basin Calibration

  • 2019 water year

Model Areas

1D Cross Sections

Colusa

Basin

Butte

Basin

Sutter Bypass

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Colusa Basin - 2019 Water Year at HWY 20

HWY 20 Gage Colusa Drain

  • Used HMS, a hydrologic model, to generate inflows for the ungaged streams in Colusa Basin

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2019 Colusa Model Calibration: Highway 20

HWY 20 Gage Colusa Drain

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2019 Colusa Model Calibration: Knight Landing Ridge Cut

Ridge Cut Slough Gage

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2019 Colusa Model Calibration: Wallace Weir

Wallace

Weir

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Field Management

Maintaining managed water levels on fields/wetlands during winter

  • Managed Rice fields
  • Private Wetlands
  • State and Federal Wetlands

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Managed fields represent typical inundation conditions derived from remotely sensed data

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Not representing year-to-year variability in managed inundation extents due to water availability

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Field Management

  • Specify typical flood-up and drawdown schedules for all wetland types​
  • Specify target depths and/or water levels​

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2019 Field Management - Colusa Basin Flood Up

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2019 Field Management - Colusa Basin Drawdown