HEC-RAS 2D Modeling with HEC-RAS

5-7 November 2024 

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 with hydraulic structures, will also be included.

Prerequisites

Participants must have a good background in open channel hydraulics and be familiar with the HEC-RAS software.  Basic HEC-RAS input and output data requirements will not be covered in this class.  Students must be experienced engineers who have attended Steady Flow with HEC-RAS, and have also either attended Unsteady Flow Modeling with HEC-RAS or have experience applying HEC-RAS using the Unsteady Flow modeling components. Participants must be in positions where they are currently engaged in using HEC-RAS in hydraulic investigations

Instructors

Cameron Ackerman, P.E., BC.WRE
Chris Nygaard, P.E.

Downloads

Requisite Software and Data

Day 1

Time
TopicObjectiveMaterialInstructor
0800-0830L0
Introductions Course Overview
Welcome and discussion of class expectations
Ackerman
0830-0915L1.1
Introduction to HEC-RAS Subgrid BathymetryDiscussion 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.

Ackerman
0915-1000L1.2
Creating an HEC-RAS Terrain
Developing a terrain model and creating dataset for 2D modeling

Nygaard
1000-1015 Break



1015-1115L1.3
Mesh Generation and Refinement and Introduction to Editing in RAS Mapper
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. 

Ackerman

1115-1215L1.4
Boundary and Initial Conditions
The different types of boundary conditions and establishing initial conditions will be discussed.

Nygaard
1215-1315 Lunch



1315-1430W1.5
Creating a Simple 2D Model Workshop
Students will create their first 2D model. Workshop - Simple 2D ModelAckerman
1430-1500
Review



1500-1515 Break



1515-1615L1.6
Visualization of HEC-RAS Results in HEC-RAS Mapper
An introduction to RAS Mapper is provided, specifically for visualizing HEC-RAS results.

Nygaard
1615-1700L1.7
Developing Manning's n Values from Land Cover Data
This lecture will describe how to create a Land Cover data set; associate Manning’s n values to Land Cover; and override Manning’s n values with 2D Manning’s n value regions

Ackerman

Day 2

Time
TopicObjectiveMaterialInstructor
0800-0900

L2.1

Essential Computation Options
Discussion of essential parameters and computational options for running a 2D model including equation choice, cell size considerations, and time step considerations.

Ackerman
0900-1030W2.2
2D Model Development and RefinementA 2D Flow Area model with be created using terrain and land cover.  Consideration of cell size, time step, and roughness coefficient values will be used in concert with mesh refinement of the model to understand the effects on model results.  RAS Mapper will be used to evaluate results.Workshop - Model Development and RefinementAckerman
1030-1100 Review



1100-1200

L2.3

SA/2D Connections

Discussion of how to use SA/2D Connections in a 2D Flow Area

Nygaard
1200-1300 Lunch



1300-1345L2.4
Terrain Modifications Demonstration
Using existing 1D cross sections for terrain modification and introduction to cloning a terrain and adding simple terrain modifications.

Ackerman
1345-1515W2.5
SA/2D ConnectionsIn 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.Workshop - 2D ConnectionsNygaard
1515-1530 Break



1530-1600 

Review




1600-1700L2.6
Bridge Modeling
This lecture will cover how to approach bridge modeling using the new 2D Bridge approach and to perform very detailed multi-dimensional hydraulic analyses.  Students will learn how to set up a model to get detailed water surfaces and velocities. 

Nygaard

Day 3

Time
TopicObjectiveMaterialInstructor
0800-0915W3.1
Bridge Modeling Workshop
Students will utilize the simplified (1D) bridge modeling approach in HEC-RAS 2D to model a bridge.

Workshop - Simplified Bridge Modeling

Ackerman

0915-0945 Review



0945-1000 Break



1000-1045L3.2

Combined 1D/2D Modeling

Discussion of modeling channels with 1D rivers reaches/cross sections combined with floodplains/levees using 2D Flow Areas

Nygaard
1045-1145W3.3
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 overtopping will also be analyzed.Workshop - Combined 1D/2D ModelingNygaard

1145-1245 Lunch



1245-1315 Review



1315-1415L3.4
Dam and Levee Breach with 2D Flow AreaDiscussion 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 entering breach parameters and estimating breach parameters.

Ackerman
1415-1430
Break



1430-1545

W3.5

Dam Breach with 2D Flow Areas WorkshopStudents will create an HEC-RAS model to utilize the breach functionality and evaluate parameters.Workshop - Dam Breach modelingAckerman
1545-1615 Review


Ackerman
1615-1700L3.6
Troubleshooting Strategies
Discussion on common model stability issues, trouble shooting strategies, and more.

Nygaard