Hydraulic Modeling with

HEC RAS Susan Cundiff, PE

December 4, 2017

Overview

Introduction to HEC RAS

Computational Procedures

Building a Model

Example Projects

Introduction to HEC RAS

U.S. Army Corps of Engineers

Hydrologic Engineering Center-River Analysis System

HEC located in Davis, CA

Download from:

http://www.hec.usace.army.mil/software/hec-ras/

What does it do?

Why HEC-RAS?

It is free!

Easy to use

1D steady state model

1D and 2D unsteady modeling

1D Sediment Transport and Mobile Boundary Modeling

Widely accepted software

1D or 2D?

Steady or Unsteady?

What questions are you trying to answer?

Floodplain inundation boundaries?

Structures

Scour/Erosion

Dam Breach analysis

Timing of flood

Flood inundation

Habitat Design

Depths

Velocities

Sediment Transport

Other considerations

Available resources

$$

Time

Available data

Computational Procedures

Steady Flow

Computation Procedures

Energy Losses, he

Computational Procedure

Conveyance Calculation

Manning’s Equation

𝑄 = 𝐾𝑆𝑓

1

2

𝐾 =1.486

𝑛𝐴𝑅

2

3

Where: K=conveyance for subdivision

n= Manning’s roughness coefficient

A=flow area for subdivision

R=hydraulic radius for subdivision

Sf = slope of the energy gradeline

Building a Model

Assemble Necessary Data

Geometry

Hydrology

Sediment Data

Building a Model

Assemble Necessary Data

Topography

Surveyed Cross Sections

DEM

Hydrology

Gage Data

HEC-HMS or other hydrology software

Bankfull, Range of flows, etc

Sediment Data

Representative Material

Appropriate transport equations

Building a Model

Geometry File

Topography

Cross sections Alignment

Hydraulic Controls

Evenly spaced

Perpendicular to Flow

Energy Losses

Channel Roughness

Horizontal Variability

Vertical Variability

Expansion and Contraction

Bridges/Structures

“I’m not bad, I was just drawn

that way.”

Building a Model

Developing the geometry data

Building a Model

Developing the geometry data

Build Quick 2D model

Building a Model

Start a New Project

Building a Model

Start New Project continued..

Building a Model

Create New Geometry

Import geometry data

CAD/GIS program

RAS Mapper

Building a Model

Editing Geometry

Bank Stations

Levees

Ineffective Flows

Blocked Obstructions

Mannings n-values

Reach Lengths

Coefficients

Building a Model

Defining Hydrology

Boundary Conditions

Normal Depth

Known WSEL

Critical Depth

Rating Curve

Building a Model

Defining Hydrology Continued

Building a Model

Defining Hydrology Continued

Building a Model

Defining Hydrology Continued

Building a Model

Sediment Data

Define Bed Gradations

Set gradation for each XS

Executing a Model

Build your Plan

Geometry

*.g0x

Hydrology

Steady*.f0x

Unsteady*.u0x

Quasiunsteady*.q0x

Sediment Data

*.s0x

Executing a Model

Options Define

Methods

Conveyance Calculations

Frictions Slope Methods

Critical Depth Calc

Tolerances

Number of iterations

WS Calcs

Sediment Transport

Model Results

Model Results

San Joaquin River Restoration

Subsidence

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

200,000 250,000 300,000 350,000 400,000 450,000

To

tal S

ub

sid

en

ce o

ver

13 y

ears

(fe

et,

)

River Station (feet, relative to the Main SJR stationline)

Reach 4A Subsidence

Upper Eastside Bypass

Middle Eastside Bypass

Chowchilla Bypass

Subsidence

SJR Sediment Transport

Geometry

Sediment Transport Modeling Results

Sediment Transport Modeling Results

Sediment Transport Modeling Results

5,500

cfs

Sediment Transport Modeling Results

References

Bender, Theodore, 2016. HEC-RAS 5.0 Presentation. Interoffice Training for

Tetra Tech.

HEC-RAS Users Manual

Gary Brunner, Army Corps of Engineers

Version 5.0.1 February 2016

Horner and Julien, 2016. CIVE 401 HEC RAS Presentation. Available at:

http://www.engr.colostate.edu/~pierre/ce_old/classes/CIVE%20401/Guest%2

0Lectures%202016/Introduction%20to%20HEC-RAS.pdf

Lai, Goy, and Julien. 2015. CIVE 401 HEC-RAS Presentation. Available at:

http://www.engr.colostate.edu/~pierre/ce_old/classes/CIVE%20401/HEC-

RAS%20Lecture/F15CIVE401%20HECRAS%20Presentation%20%28final%29-1.pdf

Contact Information

Susan Cundiff, PE | Hydraulic Engineer

Direct: 970.206.4290 | Main: 970.223.9600 Ext 4290

susan.cundiff@tetratech.com | www.tetratech.com

Tetra Tech | Science, Engineering, and Technology

3801 Automation Way, Suite 100| Fort Collins, CO 80525

Questions?