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Download page 2026 Post-Wildfire Debris Flow Modeling Application Workshop using HEC-HMS and HEC-RAS (SET Fund).
2026 Post-Wildfire Debris Flow Modeling Application Workshop using HEC-HMS and HEC-RAS (SET Fund)
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 beta (HEC-HMS-4.14-beta.1-win-x64.zip) only for this workshop. Download HEC-DSSVue potable version 3.4.18 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 latest version of HEC-RAS 6.7 beta 5 using the app portal - https://app-portal.usace.army.mil/ESD/Loader.aspx?q=webext&f=sccm or from this page, https://www.hec.usace.army.mil/software/hec-ras/download.aspx.
Hydrologic Engineering Center
- Address: 609 Second Street, Davis CA
- Located upstairs - Enter through double glass doors between Davis Wine Bar and Toy Store. Doors remained locked until 7:15am
- There is an additional locked door at the top of the stairwell. For the morning of the first day of class, these doors will be unlocked. A doorbell is available if needed.
Parking Downtown Davis
- All day parking options for visitors:
4th & G Street Garage (835 4th St) -
Rates:
3 hours Free
$1 per hour after 3 hours.
$5 max daily rate.
- E Street Plaza
- Rates: $1/hour
- Further information: https://davisdowntown.com/parking-transportation/parking/#eae334765018be3dc
- All day parking options for visitors:
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., Watershed Scale Sediment and Post-fire Hydrology/Debris Flow Analysis Specialist on the HEC-HMS Team, US Army Corps of Engineers, Hydrologic Engineering Center (HEC)
- Daniel Black, Hydrologist, US Army Corps of Engineers, Hydrologic Engineering Center (HEC)
- Jose Paredez, P.E., Lead Civil Engineer, Hydrology Section, USACE Los Angeles District (SPL)
- Stanford Gibson, PhD, Sediment Specialist on the HEC-RAS Team, Hydrologic Engineering Center (HEC)
- Alex Sanchez, PhD, Developer of the 2D DebrisLib algorithms, Hydrologic Engineering Center (HEC)
Pre-Read/Watch
Please watch or read these materials before the class.
- If you have never used HEC-RAS 2D this class jumps right into the non-Newtonian application of 2D RAS. You may want to take some time to familiarize yourself with this online class: https://www.hec.usace.army.mil/confluence/rasdocs/rastraining/latest/hec-ras-classes/2d-unsteady-flow-2021
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, safety, facility briefing, etc. | Jay Pak Stan Gibson | ||
08:30 - 9:30 | 60 | Lecture | Lecture 1: Overview of Hydrologic Modeling with HEC-HMS Discussion about model calibration, Frequency Storm and Hypothetical Storm development, and continuous simulation | Daniel Black | ||
9:30 – 9:45 | 15 | Break |
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9:45 - 11:00 | 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 | ||
11:00 - 11:45 | 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 or Daniel Black | ||
11:45 - 12:45 | 60 | Lunch | Networking |
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12:45 - 13:45 | 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. | Daniel Black Jay Pak Jose Paredez | ||
13:45 - 14:00 | 15 | Workshop Review |
| Daniel Black | ||
14:00 - 14:45 | 45 | Lecture | Lecture 4: Channel Sediment Routing in HEC-HMS Overview of channel sediment routing processes and methods in HEC-HMS. | Jay Pak | ||
14:45 - 15:00 | 15 | Break |
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15:00 - 16:00 | 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 | ||
16:00 - 16:45 | 45 | Lecture | Special Lecture: Long-Term Post-Fire Application | 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 | Jay Pak |
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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. | Daniel Black Jay Pak Jose Paredez | ||
09:45 - 10:00 | 15 | Workshop Review |
| Daniel Black | ||
10:00 – 10:15 | 15 | Break | Training Class Photo | |||
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). | Daniel Black Jay Pak Jose Paredez | ||
12:10 – 13:10 | 60 | Lunch | Networking | |||
13:10 - 13:25 | 15 | Workshop Review |
| Daniel Black | ||
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| Special Lecture |
| Dustin Michel | ||
13:25 - 14:25 | 60 | 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. | Jay Pak & Jose Paredez | ||
14:25 – 15:00 | 35 | Lecture | Lecture 8: Outlet Tower Procedures for defining and Adjusting Outlet Tower geometry and operational parameters within the Reservoir Element. | Jay Pak | ||
15:00 – 15:15 | 15 | Demo | Demo: Intake Tower Bailey Outlet Tower | Jay Pak | ||
15:15 – 15:30 | 15 | Break | Post-Wildfire Watershed Management: San Bernardino County DPW | |||
15:30 - 15:50 | 20 | Lecture | Lecture 9: Miami Fire (AZ) Debris Basin Design | Jose Paredez | ||
15:50 - 16:00 | 10 | Demo | Demo: Debris Basin Design Case Study (Miami Fire, AZ) | Jose Paredez | ||
16:00 - 16:15 | 15 | 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 | ||
16:15 - 16:30 | 15 | Demo | Demo: Real-Time Simulation using Precipitation Forecast Implementing real-time flood forecasting with HEC-HMS for Bailey Debris Basin. | Jose Paredez | ||
16:30 – 17:00 | 30 | Knowledge Sharing/Group Discussion | All |
Day 3: Wednesday, 1 Apr 2026
Time | Duration (min) | Module | Topic | Description |
8:00-8:45 | 45 | Presentation 1 (3.1 L) 3.1 - Modeling Mud and Debris Flows (Example Applications).pdf | Overview of non-Newtonian applications of HEC-RAS, including lab and prototype scale studies. | |
8:45- 9:30 | 45 | Presentation 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. |
9:30-9:45 | 15 | Break | ||
9:45- 11:30 | 75 | Presentation 3 (3.3W) | 2D Hydraulic Modeling with HEC-RAS Files:  Simple 2D Workshop Starting Files.zip | Students build a simple HEC-RAS model.
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11:30– 12:30 | 60 | Lunch | ||
12:30-13:30 | 60 | Lecture 3 (3.4L) | Introduces the internal stress term in the hydraulic equations and the rheological models that estimate it. | |
13:30-13:45 | 15 | Quiz Game (3.5Q) | Non-Newtonian Mechanics | Review the Non-Newtonian Physics covered in the previous talk. |
13:45-14:30 | 45 | Expedited Debris Flow Modeling in HEC-RAS | Build a non-Newtonian debris flow model from a single shape file. | |
14:30-14:45 | 15 | Break | ||
14:45-15:45 | 45 | Workshop 2 | ||
15:45-16:45 | 60 | Presentation 4 (3.7L) | 2D Hydraulic and Subgrid Best Practices and Troubleshooting | Introduces best practices for developing a stable 2D hydraulic model in steep terrain. |
16:45-17:00 | 15 | Quiz Game (3.8Q) | Mesh Doctor Game | Competitive game where students identify problematic meshes and/or potential fixes |
Day 4: Thursday, 2 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. |
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. |
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. |
11:00-12:00 | 60 | Lecture 11 (4.3) 4.3L Selecting Rheological Parameters (2026).pdf | 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. | |
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 |
13:15-13:30 | 15 | Presentation 5 (4.5 L) | Urban and High Gradient Debris Modeling | Modeling clogged culverts and bridges with a 2D RAS Model (and common stability issues). |
13:30-13:45 | Demo | Meshing with RAS2025 | We will introduce the new meshing capabilities in RAS2025 which will improve every aspect of these analyses in the future. | |
13:45-15:30 | 120 | Final HEC-HMS/ HEC-RAS Modeling Workshop HMS_Starting_Files_Final_Workshop.zip HMS_Starting_Files_Final_Workshop.7zRAS Starting Files Final Workshop.zip | 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 | |
15:30-16:00 | 15 | Break | ||
16:00– 16:30 | 30 | Workshop 8 review | ||
16:30 – 17:00 | 30 | Group Discussion | Class Review and Future Needs | |
