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Download page Draft: 2026 Post-Wildfire Debris Flow Modeling Application Workshop using HEC-HMS and HEC-RAS (SET Fund): Under Development.
Draft: 2026 Post-Wildfire Debris Flow Modeling Application Workshop using HEC-HMS and HEC-RAS (SET Fund): Under Development
Workshop Objectives:
The USACE Hydrologic Engineering Center (HEC) has expanded its hydrologic and hydraulic modeling software to better support debris-flow hazard assessment. HEC’s Hydrologic Modeling System (HEC‑HMS) can compute debris yield and debris flow, and HEC’s River Analysis System (HEC‑RAS) can simulate the non‑Newtonian behavior of mud and debris flows—capabilities applicable to post‑wildfire events and mine‑tailings dam breaches.
This four‑day, hands‑on workshop provides practical, application‑focused training on applying these tools to post‑wildfire flood and debris‑flow analyses.
Participants will:
- Understand how HEC‑HMS and HEC‑RAS support post‑wildfire hydrology and debris‑flow modeling.
- Gain hands‑on experience building end‑to‑end post‑wildfire hydrologic and hydraulic models, including parameter estimation, calibration, and implementation in HEC‑HMS and HEC‑RAS.
It is recommended that you use this specific version of HEC-HMS for this workshop and HEC-DSSVue version 3.4.15 for the class. You do not need administrative privileges to install HEC-HMS and HEC-DSSVue. Download HEC-HMS special potable testing version 4.14 alpha (HEC-HMS-4.14-alpha-win-x64_HMS-4430.zip) only for this workshop. Download HEC-DSSVue version 3.4.15 from this page, https://www.hec.usace.army.mil/software/hec-dssvue/downloads.aspx. Then use 7-zip and unzip the files to the C:\Programs directory on your computer (you should have a folder named HEC-HMS-4.13-beta within the C:\Programs directory). Then you can pin HEC-HMS.exe and HEC-DSSVue.exe to your taskbar and open these programs by clicking on the icons. You do need to install HEC-RAS 6.3.1 using the app portal - https://app-portal.usace.army.mil/ESD/Loader.aspx?q=webext&f=sccm.
Workshop Details
- Time: 30 March – 2 April 2026, 0800–1700 (daily)
- Location: USACE Hydrologic Engineering Center (HEC), 609 Second St., Davis, CA 95618
- Instructor:
- Jay Pak, Ph.D., P.E., Sr. Research Hydraulic Engineer, US Army Corps of Engineers, Hydrologic Engineering Center (HEC)
- Daniel Black
- Stanford Gibson
- Alex Sanchez
- Cameron Ackerman
- Instructor Short Biography:
Dr. Jang (Jay) Pak boasts over two decades of experience with the US Army Corps of Engineers (USACE), currently serving as a Senior Research Hydraulic Engineer at the Hydrology & Statistics Division of the Hydrologic Engineering Center (HEC). His expertise encompasses surface water hydrology, post-fire hydrology, river hydraulics, debris flow analysis, land surface erosion, and more. Dr. Pak earned his Ph.D. and Master’s degrees in Civil and Environmental Engineering from the University of Southern California, focusing his doctoral research on real-time debris prediction models integrating wildfire and subsequent storm events. He is a registered civil engineer in the state of California.
Workshop Agenda:
Day 1: Monday, 30 March 2026
Time | Duration (min) | Module | Topics | Instructor(s) | Links to Materials | Presentation Slides |
08:00 - 08:30 | 30 | Admin | Welcome, introductions Logistics, bathrooms, etc. | Jay Pak Stan Gibson | ||
08:30 - 09:30 | 60 | Overview of 2025 Wildfire Study | Discussions of methods, assumptions, and limitations: Hydrology (Curve Number/G&A), Sedimentation Yield, Reservoir Routing, and Hydraulics | Jose Paredez Moosub Eom Nicholas Olsen |
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09:30 - 09:45 | 15 | Break |
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09:45 - 10:30 | 45 | Lecture | Lecture 1: Overview of Hydrologic Modeling with HEC-HMS Discussion about model calibration, Frequency Storm and Hypothetical Storm development, and continuous simulation | Jose Paredez | ||
10:30 - 11:45 | 75 | Lecture | Lecture 2: Overview of Post-Wildfire Hydrology and Debris Flow Modeling Applications Discussion of the ways post-wildfire hydrology and debris yield modeling is used in studies including post-wildfire assessments, debris yield prediction, and post-wildfire flow risk and emergency management. | Jay Pak | ||
11:45 - 12:45 | 60 | Lunch |
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12:45 - 13:30 | 45 | Lecture | Lecture 3: Subbasin Debris Yield Analysis Introduction to five debris yield methods for debris yield assessment in burned mountain watershed. Discussion of appropriate use and parameter estimation. | Jay Pak | ||
13:30 - 14:30 | 60 | Workshop | Workshop 1: Quick Debris Yield Modeling based on Field Data Estimate the parameters for each debris yield method. Enter the initial parameter values within a basin model, create a simulation run, and compute the simulation. Calibrate and compare results to measured sample data. | Jay Pak Jose Paredez Moosub Eom Nicholas Olsen Jackie Oehler | ||
14:30 - 14:45 | 15 | Workshop Review |
| Jackie Oehler | ||
14:45 - 15:00 | 15 | Break |
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15:00 - 15:45 | 45 | Lecture | Lecture 4: Channel Sediment Routing in HEC-HMS Overview of channel sediment routing processes and methods in HEC-HMS. | Jay Pak | ||
15:45 - 16:45 | 60 | Lecture | Lecture 5: Debris Reservoir Routing Analysis Explanation of the physical reservoir volume reduction processes at reservoir. The reservoir sediment trap efficiency is affected by the detention time of storm runoff and by factors governing sediment particle size. | Jay Pak | ||
16:45 - 17:00 | 15 | Group Discussion |
| All |
Day 2: Tuesday, 31 March 2026
Time | Duration (min) | Module | Topics | Instructor(s) | Links to Materials | Presentation Slides |
| 08:00 - 08:15 | 15 | Admin | Recap and Review | Jose Paredez |
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08:15 - 09:45 | 90 | Workshop | Workshop 2: Estimating Debris Yield in Debris Basin Practice calibrating debris yield modeling without/with Debris Reservoir/Basin and compare results with measured data. | Jay Pak Jose Paredez Moosub Eom Nicholas Olsen Jackie Oehler | Old Task 2: Debris Yield Modeling without Debris Basin (with New Debris Volume Conversion to Mass Unit Weight/Density) (Sediment Restructure: HMS 4.14) Optional: Old Task 3: Debris Yield Modeling with Debris Basin (with New Debris Volume Conversion to Mass with Unit Weight/Density) (Sediment Restructure: HMS 4.14) | |
09:45 - 10:00 | 15 | Workshop Review |
| Jackie Oehler | ||
10:00 – 10:15 | 15 | Break | ||||
10:15 - 11:00 | 45 | Lecture | Lecture 6: Post-Wildfire Hydrologic Analysis: Event & Continuous Models Explanation of a surface dynamic infiltration loss method to develop a long-term post-wildfire hydrologic model for a burned watershed. Discussion of the physical basis for the parameters and procedures for post-wildfire effect. | Jay Pak | ||
11:00 - 12:10 | 70 | Workshop | Workshop 3: Post-Wildfire Hydrology Analysis using Surface Dynamic Infiltration Loss Method: Use a surface dynamic infiltration loss method to estimate parameters for the long-term post-wildfire hydrology model. Practice calibrating model and compare results with observed flow (gage data). | Jay Pak Jose Paredez Moosub Eom Nicholas Olsen Jackie Oehler | ||
12:10 – 13:10 | 60 | Lunch | Lunch / Networking | |||
13:10 - 13:25 | 15 | Workshop Review |
| Jackie Oehler | ||
13:25 - 14:20 | 55 | Lecture | Lecture 7: Post-Wildfire Hydrologic Analysis: CN Loss Method and G&A Method Explanation of two principal approaches for estimating post-fire infiltration loss: The NRCS Curve-Number (CN) method and the Green-Ampt (G&A) method. | |||
14:20 – 15:05 | 45 | Lecture | Lecture 8: Model Calibration Optimizing hydrologic and sediment yield predictions: A calibration approach using historical precipitation and streamflow records. | Jackie Oehler | ||
15:05- 15:45 | 40 | Demo/Workshop | Demo 1: Calibration Calibrating hydrologic parameters using historical precipitation and streamflow records | Jackie Oehler | ||
15:45 - 16:00 | 15 | Break | ||||
16:00 – 16:30 | 30 | Lecture | Lecture 9: Outlet Tower Procedures for defining and Adjusting Outlet Tower geometry and operational parameters within the Reservoir Element. | Jackie Oehler | ||
16:30 – 16:45 | 15 | Demo | Demo 2: Intake Tower Bailey Outlet Tower | Jackie Oehler | ||
16:45 – 17:00 | 15 | Group Discussion | All |
Time | Duration (min) | Module | Topics | Instructor(s) | Links to Materials | Presentation Slides |
08:00 - 08:15 | 15 | Admin | Recap and Preview | Jose Paredez |
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08:15 – 08:45 | 30 | Demo | Demo 3: Calibration a reservoir element Calibrate debris-basin sediment yield and sediment-surface elevation using observed measurements | Jackie Oehler | ||
08:45 – 09:30 | 45 | Lecture | Lecture 10: Real-Time Simulation using Precipitation Forecast Implementing real-time flood forecasting with HEC-HMS: Procedures for data acquisition, model development, and simulation runs. | Jose Paredez | ||
09:30 – 10:00 | 30 | Demo | Demo 4: Real-Time Simulation using Precipitation Forecast Implementing real-time flood forecasting with HEC-HMS for Bailey Debris Basin. | Jose Paredez | ||
10:00 - 10:15 | 15 | Break | ||||
10:15 - 11:00 | 45 | Lecture | Lecture 11: Post-Wildfire Hydraulic Analysis Explanation of non-Newtonian flow models in HEC-RAS, which are used to account for internal losses affecting the md and debris flows. | Moosub Eom Nicholas Olsen | ||
11:00 – 12:30 | 90 | Demo | Demo 5: Debris flow modeling Debris flow inundation mapping application using the non-Newtonian models in HEC-RAS. | Moosub Eom Nicholas Olsen | ||
12:30 - 13:30 | 60 | Lunch | ||||
13:30 - 14:15 | 45 | After-Action Review |
| Jose Paredez | ||
14:15 - 17:00 | 165 | Knowledge Sharing | LA District Planner: DWR: CGS: LACDPW: | All |
Day 3: Wednesday, 1 Apr 2026
Time | Duration (min) | Module | Topic | Description | Primary Instructor |
8:00-8:45 | 45 | Lecture 1 (3.1 L) | Modeling Mud and Debris Flows with HEC-RAS | Overview of non-Newtonian applications of HEC-RAS, including lab and prototype scale studies. | Stanford |
8:45- 9:30 | 45 | Lecture 2 (3.2L) | Overview of HEC-RAS | Introduction to the basic components and workflow of an unsteady, 2D, “blue water” (no debris) HEC-RAS model. | Stanford |
9:30-9:45 | 15 | Break | |||
9:45- 11:30 | 75 | Workshop 1 (3.3W) | 2D Hydraulic Modeling with HEC-RAS | Students build a simple HEC-RAS model.
| Stanford Alex Cam |
11:30– 12:30 | 60 | Lunch | |||
12:30-13:30 | 60 | Lecture 3 (3.4L) | Introduction to Non-Newtonian Physics | Introduces the internal stress term in the hydraulic equations and the rheological models that estimate it. | Stanford |
13:30-13:45 | 15 | Quiz Game (3.5Q) | Non-Newtonian Mechanics | Review the Non-Newtonian Physics covered in the previous talk. | Stanford |
13:45-14:30 | 45 | Workshop 2 (3.6W) | Expedited Debris Flow Modeling in HEC-RAS | Build a non-Newtonian debris flow model from a single shape file. | Stanford Alex |
14:30-14:45 | 15 | Break | |||
14:45-15:45 | 45 | Workshop 2 | Continued | Solution Files | Stanford |
15:45-16:45 | 60 | Talk 4 (3.7L) | 2D Hydraulic and Subgrid Best Practices and Troubleshooting | Introduces best practices for developing a stable 2D hydraulic model in steep terrain. | Stanford |
16:45-17:00 | 15 | Quiz Game (3.8Q) | Mesh Doctor Game | Competitive game where students identify problematic meshes and/or potential fixes | Stanford |
Day 3: Wednesday, 1 Apr 2026
8:00-9:00 | 45 | Workshop 3 (4.1W) | Model Refinement and Stability Workshop | Students will rerun workshop 2 with the full SWEs and work on the mesh and time step to improve stability. | Stanford Alex |
9:00 – 10:30 | 90 | Lab (4.2 Lab) | Non-Newtonian Flow “Race” | Students will mix bulked fluids with non-Newtonian properties to try to get closest to a time goal. | Stanford Alex |
10:30– 10:45 | 15 | Break | |||
10:45-11:00 | 15 | Lab Review | Lab Review | Plot the student mixtures on the ternary diagram and develop some conclusions. | Stanford |
11:00-12:00 | 60 | Lecture 11 | Selecting Rheological Parameters | The most difficult part of most mud and debris models is estimating the Rheological Parameters. This talk will survey the laboratory and modeling literature, introduce some of the established trends, explore the sensitivity of the mudplain extents to some of these parameters, and provide reasonable modeling ranges to help modelers bound their answers. | Stanford |
12:00– 13:00 | 60 | Lunch | |||
13:00-13:15 | 15 | Quiz Game | Parameter Quiz | Students will review different model parameterizations and evaluate them…for points and glory. www.kahoot.it | Stanford |
13:15-13:30 | 15 | Lecture 5 | Urban Debris Modeling | Modeling clogged culverts and bridges with a 2D RAS Model (and common stability issues). | Stanford |
13:30-15:30 | 120 | Workshop 7 (4.6 W) | Final HEC-HMS/ HEC-RAS Modeling Workshop | Start with clear water HMS and RAS models. Add HMS parameters and compute Cv. Use HMS Cv and NN parameters to model debris flow in HEC-RAS | Stanford Alex HMS Team |
15:30-16:00 | 15 | Break | |||
16:00– 16:30 | 30 | Workshop 8 review | Santa Cruz Workshop | Stanford | |
16:30 – 17:00 | 30 | Group Discussion | Class Review and Future Needs | HEC Team | |
Class Evaluation and Feedback: | |||||
