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Steady Flow HEC-RAS
This course teaches the concepts of open channel flow concepts, hydraulic model data requirements, HEC-RAS input requirements, laying out cross sections for 1D hydraulic modeling, application of bridge and culvert routines, calibration of a steady flow hydraulics model, floodway determination, an overview of Optional capabilities, and output analysis. The HEC-RAS software will be included in lectures and workshops. Participants have an opportunity to prepare input and analyze output during workshops.
Class Materials
Any use or reproduction of this material must be attributed to the US Army Corps of Engineers Hydrologic Engineering Center.
Modeling River Hydraulics with HEC-RAS
| Topic | Video | Material |
|---|---|---|
| Steady Flow Overview, Applications, and Components (L1.1) Case studies (why steady flow is important). Model selection between 1D and 2D. Steps in setting up a model and RAS file management. | ||
| Geometric Data Requirements for Water Surface Profile Calculations (L1.2) Study limit determination; defining the river system schematic; cross section geometry and locations; optional cross section properties: ineffective flow areas, levees, and blocked obstructions; defining the reach lengths between sections; energy loss coefficients; stream junction data. | ||
Laying out Cross Sections Workshop (W1.3) Students draw cross sections on four maps using the orthogonality and hydraulic control principles from the previous talk. | ||
Geometric Data Development with RAS Mapper (L1.4) This lecture will go through developing an HEC-RAS terrain model, river network, and entering and editing data tools in RAS Mapper. | ||
| Developing HEC-RAS Geometry Workshop (W1.5) | Students will create a new HEC-RAS terrain layer, layout the model schematic and cross sections. | |
Water Surface Profile Calculation (L1.6) Classifications of open channel flow; velocity distribution in a channel; energy principles; cross section subdivision for conveyance calculations; friction loss equations; contraction and expansion losses; computational procedure; critical depth determination; and applications of the momentum equation. |
Developing a Model and HEC-RAS Bridge Analysis
| Topic | Objective | Material |
|---|---|---|
Steady Flow Data Requirements (L2.1) Discussions about flow regime; boundary conditions; discharge information | ||
Resistance to Flow (L2.2) Discussions about Manning’s equation; uniform flow equations; methods for computing n values: tables, pictures, and equations; examples of calibrated n values for various streams. | ||
Viewing Results (L2.3) Viewing results; cross section plots; profile plot; X-Y-Z plot; summary tables; errors, warnings, and notes, and floodplain maps in RAS Mapper. | ||
| 1D Model Development and Evaluating Results (W2.4) | Students will learn to create an HEC-RAS model, complete geometry, enter flow data, perform the hydraulic computations, and view results | |
Bridge Hydraulics for 1D Modeling (L2.5) Nature of flow through bridges; components of bridge losses; cross-section locations; defining ineffective flow areas; contraction and expansion losses. | ||
| Bridge Modeling Approaches in HEC-RAS (L2.6) Available approaches to bridge loss computations within HEC-RAS; selecting the appropriate bridge modeling approach for various situations of low flow bridge hydraulics; selecting the appropriate bridge modeling approach for various situations under high flow bridge hydraulics. | ||
| 1D Model Development and Evaluating Results (W2.7) | Demonstration of how to enter and edit bridge data; defining a bridge modeling approach; bridge modeling options; pertinent bridge output. | |
| 1D Model Development and Evaluating Results (W2.8) | Students will learn to enter and edit bridge data for performing bridge hydraulic computations. |
HEC-RAS Bridge and Culvert Hydraulics
| Topic | Objective | Material |
|---|---|---|
| Bridge Analysis Workshop (W3.1) | Students will focus on solving the bridge solution for mass conservation. | |
Overview of Culvert Hydraulics (L3.2) Definition of terms; input requirements: cross section locations, ineffective flow areas, expansion and contraction coefficients; inlet control; outlet control; solution logic | ||
| Application of HEC-RAS to Culvert Hydraulics (D3.3) | Demonstration of how to enter and edit culvert data; culvert modeling options; review of culvert output | |
| Culvert Analysis (W3.4) | Students will learn how to enter and edit culvert data, perform culvert hydraulic computations; and review pertinent output | |
Inundation Map Tools (L3.5) Students will learn to use RAS Mapper tools for improving inundation mapping | ||
| Overview of Optional Capabilities (L3.6) | Cross section interpolation; mixed flow regime calculations; flow distribution calculations; lateral structures and optimization; Inline Weirs and Gated Spillways. |
Model Calibration, Optimal Capabilities and Floodway Determination
| Topic | Objective | Material |
|---|---|---|
Calibrating a Steady Flow Model (L4.1) Students will learn what data is required for model calibration and how to modify Manning’s n values to calibrate the model to observed data. | ||
| Model Calibration Workshop (W4.2) | Students will learn how to modify Manning’s n values to calibrate the model to observed data | |
| Troubleshooting with HEC-RAS (L4.3) | This lecture will provide students with information on how to interpret HEC-RAS output messages (errors, warnings, and notes); diagnose common data input mistakes; and how to use the HEC-RAS Log File to understand more about the computations and possible problems | |
| Troubleshooting Workshop (W4.4) | This workshop will teach students how to analyze the HEC-RAS output in order to detect common hydraulic modeling problems. |
HEC-RAS Trouble Shooting and Output Analysis
| Topic | Objective | Material | |
|---|---|---|---|
| L5.1 | Floodplain and Floodway Determination | Floodway definitions; general guidelines; computer procedures; program input requirements for floodway calculations; available output. | |
| W5.2 | Floodway Determination | Students will learn how to enter and edit encroachment data and perform a floodway analysis. | |
| Develop storage outflow curves | This demo will show you how to use output from HEC-RAS to set up routing reach properties in HEC-HMS. | Using an HEC-RAS Model to Create Storage-Discharge Curves for Mod-Puls Reaches in HEC-HMS | |
| Channel modification and terrain mods | This presentation will discuss how to use channel modifications in RAS Mapper. | ChannelMod and TerrainMod.pptx |