2D Unsteady Flow (2026)

PROSPECT Course #352

Objectives

This is an advanced course in applying computer program HEC-RAS. The course provides participants with the knowledge to effectively use computer program HEC-RAS to analyze difficult hydraulic conditions in natural and constructed channels, utilizing one-dimensional and two-dimensional modeling techniques.

Topics include: Developing terrain models for 2D modeling; developing Manning’s n layers; creating and modifying a 2D computational mesh; boundary conditions for 2D Flow Areas; hooking up 1D elements to 2D Flow Areas; running a combined 1D/2D model; viewing 1D/2D results with RAS Mapper; hydraulic structures inside of 2D areas; and detailed channel and floodplain modeling with 2D flow areas. Special topics for dam and levee breaching, and using 2D modeling for hydraulic structures, will also be included.

Instructors

Wesley Crosby (Course Coordinator)
Heath Sand
Russ Wyckoff
Jake Allgeier
Cameron Ackerman
Stanford Gibson
Alex Sanchez

Class Materials

Workshops were developed with HEC-RAS version 6.6.

Terms of Use

Any use or reproduction of this material must be attributed to the US Army Corps of Engineers Hydrologic Engineering Center.

Day 1

Time		Topic	Objective	Material
0800-0900	L0	Introductions and pre-course activities	Welcome and discussion of class expectations
0900-0945	L1.1	Example HEC-RAS Modeling	Overview of HEC-RAS capabilities using example applications for 2D modeling Introduction to the validation and verification of HEC-RAS. A demonstration of using HEC-RAS to create a 2D model will conclude the discussion.
0945-1000		Break
1000-1100	L1.2	Introduction to the 2D Equations	This presentation discusses the underlying 2D hydraulic equations used in HEC-RAS. Diffusion Wave and Full Shallow Water Equations in HEC-RAS will be discussed as well as scenarios where the equations are appropriate is also provided.
1100-1145	L1.3	Subgrid Bathymetry	Discussion on the use of sub-grid bathymetry for finite volume computations in HEC-RAS. The benefits of variable cell size on computational performance will be discussed.
1145-1245		Lunch
1245-1345	L1.4	Creating an HEC-RAS Terrain	Developing a terrain model and creating dataset for 2D modeling. Introduction to terrain download capabilities.
1345-1445	W1.5	Creating an HEC-RAS Terrain Workshop	Hands- on work creating an HEC-RAS Terrain dataset	Creating a RAS Terrain Workshop
1445-1500		Break
1500-1545	L1.6	Mesh Generation and Refinement	This presentation will discuss the basic concepts of creating a 2D Mesh in HEC-RAS and then how to improve and refine a 2D Mesh with Breaklines and Refinement Regions. Examples of mesh quality will be reviewed.
1545-1700	W1.7	Mesh Generation and Refinement Workshop	This workshop will provide hands-on experience in using HEC-RAS Mapper to create a 2D flow area mesh and refine it to capture high ground using breaklines and refinement regions	Mesh Generation and Refinement Workshop

Day 2

Time		Topic	Objective	Material
0800-0845	L2.1	Boundary and Initial Conditions	The different types of boundary conditions and establishing initial conditions will be discussed.
0845-0930	L2.2	Computational Parameters	Discussion of essential parameters and computational options for running a 2D model including equation choice, cell size considerations, and time step considerations.
0930-0945		Break
0945-1100	W2.3	Creating a Simple 2D Model Workshop	Students will create their first 2D model. Refinement of the model will be performed to understand the effect of model parameters.	Creating a Simple 2D Model
1100-1130		Review
1130-1230		Lunch
1230-1315	L2.4	Visualization of HEC-RAS Results in HEC-RAS Mapper	An introduction to RAS Mapper is provided, specifically for visualizing HEC-RAS results.
1315-1345	D2.5	HEC-RAS Mapper Demonstration
1345-1400		Break
1400-1430	L2.6	Land Classification Data	This discussion will cover creating an Land Classification dataset for use with Manning's n values in RAS Mapper.
1430-1515	W2.7	Land Classification Data	Student will learn how to bring land cover data into a Land Classification dataset and associated Manning's n values.	Land Cover and Manning's "n" Data Workshop
1515-1545		Review
1545-1600		Kahoot!
1600-1630	L2.8	Advanced Computation Options	Discussion of more advanced parameters and computational options for running a 2D model including equation choices, turbulence, and matrix solvers.
1630-1700	L2.9	1D vs 2D Modeling	This presentation discusses 1D vs 2D modeling and how to choose the appropriate modeling method.

Day 3

Time		Topic	Objective	Material
0800-0830	L3.1	Dam Breach with 2D Flow Area	Discussion of how to use 2D Flow Areas with 1D reaches and storage areas to perform a dam breach analysis. Discussion on using the SA/2D Connection for modeling a dam, outlets, and the dam breach.
0830-0900	L3.2	Determination of Dam Breach Parameters	This presentation will discuss estimating dam breach parameters for modeling dam breach scenarios.
0900-0915		Break
0915-1045	W3.3	Dam Breach with 2D Flow Areas Workshop	Students will create an HEC-RAS model to utilize the breach functionality and evaluate parameters.	2D Dam Breach Analysis Workshop
1045-1100		Review
1100-1130	L3.4	Combined 1D/2D Modeling	Discussion of modeling channels with 1D rivers reaches/cross sections combined with floodplains/levees using 2D Flow Areas
1130-1230		Lunch
1230-1345	W3.5	Combined 1D/2D Modeling Workshop	Use a combined 1D/2D model to evaluate a protected area using 2D Flow Area and a Lateral Structure to define a levee. Levee over-topping and breaching will also be analyzed.	Combined 1D/2D Modeling Workshop
1345-1415		Review
1415-1430		Break
1430-1445		Kahoot!
1445-1515	L3.6	SA/2D Connections	Discussion of how to use SA/2D Connections in a 2D Flow Area
1515-1545	D3.7	Terrain Modifications Demonstration	Introduction to cloning a terrain and adding a simple terrain modification.
1545-1645	W3.8	SA/2D Connections	In this workshop, students will utilize 2D Connections (internal hydraulic structures) inside of a 2D Flow Area to improve the river hydraulics model by overriding terrain elevations.	2D Connections Workshop
1645-1700		Review

Day 4

		Topic	Objective	Material
0800-0825	L4.1	2D Calibration Principles	An overview of 2D model calibrations will be provided.
825-830		Download RAS2025	https://www.hec.usace.army.mil/software/hec-ras/2025/
0830-0945	L4.2	Troubleshooting Strategies	Discussion on common model stability issues, troubleshooting strategies, and more.
0945-1000		Break
1000-1130	W4.3	Troubleshooting Workshop	Students will investigate 2D modeling problems and model fixes.	Troubleshooting a 2D Model
1130-1200		Review
1200-1300		Lunch
1300-1345	L4.4	Bridge Modeling	Discussion on modeling a bridge using a 2D Connection using the 1D bridge modeling method as well as developing a detailed mesh to represent the flow constriction.
1345-1515	W4.5	Bridge Modeling Workshop	Students will utilize the 1D bridge modeling approach to modeling as well as develop a detailed bridge model to evaluate water surface elevations and velocities in detail.	Simplified 2D Bridge Modeling Workshop
1515-1530		Break
1530-1600		Review
1600-1615		Kahoot!
1615-1700	L4.6	Precipitation and Wind	This presentation will discuss the use of the Precipitation and Wind boundary condition in HEC-RAS.

Day 5

Time		Topic	Objective	Material
0800-0900	W5.1	Precipitation and Wind Workshop	Students will utilize precipitation to create a rain on grid model.	Meteorological Data Workshop
0900-0915		Review
0930-1000	L5.2	Intro to Meshing in HEC-RAS 2025	Discussion of the HEC-RAS 2025 Conceptual Mesh and the mesh import capability in HEC-RAS 7.
1000-1100	D5.3	Using an HEC-RAS 2025 Mesh in HEC-RAS 7	Demonstration of creating and editing a mesh in HEC-RAS 2025 and importing it into HEC-RAS 7. Terrain.RASMeshWorkshopTerrain.tif	Mesh Development for HEC-RAS 7
1100-1130		Course Closing	Post-test, course evaluations, oral critique, and closing remarks