Hec-RAS from Zero for Hydraulic Flood Analysis

This lecture introduces the fundamental flow theory necessary to understand how HEC-RAS analyzes and models hydraulic flows. It explains the complex nature of open channel flows, highlighting their variations over time and space, which require simplifications for practical analysis.

The focus is on explaining key hydrodynamic principles such as flow continuity, uniformity, and the concept of normal depth within channels of varying geometry. The lecture establishes the theoretical groundwork that supports the modeling of one-dimensional and steady-state flow conditions that the course emphasizes.

Concepts such as water surface profiles, conservation of mass through the continuity equation, and energy balance between sections are presented to illustrate flow behavior. The lecture also covers specific energy, critical depth, and introduces the Froude number to classify flows as subcritical or supercritical based on dominant forces.

Key topics covered:

• Complexities of open channel flow and simplifications for modeling

• Continuity and uniformity assumptions in flow analysis

• Definitions of normal depth and water surface profiles

• Application of continuity and energy balance equations

• Concept of specific energy and critical depth

• Froude number and classification of flow regimes

• Focus on one-dimensional, steady-state flow modeling

Practical value for hydraulic modeling:

• Understanding flow behavior to create accurate hydraulic models

• Applying hydrodynamic principles to simplify complex flow scenarios

• Utilizing flow classifications for improved model calibration

• Preparing to build steady-state, one-dimensional HEC-RAS projects with sound theoretical support

By completing this lecture, learners will grasp the essential flow theory concepts that underpin hydraulic modeling in HEC-RAS, enabling them to apply these principles effectively in one-dimensional steady flow analyses within the software.

This lecture guides you through the practical workflow of creating a basic HEC-RAS project from scratch. You will start by setting the measurement units to SI, establishing the project folder, and naming the project correctly to avoid file issues.

The session focuses on introducing river geometry by drawing and importing river sections, defining river reaches, and entering cross-sectional data to represent the riverbed accurately. You will also learn how to add multiple cross sections, including their locations, elevations, and Manning’s roughness values, which control flow resistance.

Once the geometry is established, the lesson proceeds to steady flow data input by defining flow profiles for different return periods, introducing flow rates, and setting boundary conditions such as normal depth. Finally, you'll run a steady flow simulation to check for errors and visualize results in both 3D and tabular formats, including flood levels and hydraulic parameters.

Key topics covered in this lecture:

• Project setup and unit system configuration.

• Creating and saving geometry with river reaches and cross sections.

• Inputting cross-sectional station, elevation, and roughness details.

• Managing flow data with profiles, flow rates, and boundary conditions.

• Running steady flow simulations and interpreting error feedback.

• Visualizing model results in 3D plots and data tables.

• Interpolating cross sections between existing reaches to improve model accuracy.

Practical value for hydraulic modeling:

• Build a fully functional basic flood model with geometry and flow data.

• Understand how to input essential river and flow characteristics correctly.

• Identify and resolve common data errors during simulation setup.

• Generate visual and numerical outputs to evaluate flood behavior.

• Apply interpolation techniques to refine the model geometry.

By the end of this lecture, you will be able to create a simple but complete HEC-RAS hydraulic model with multiple river sections, configure flow profiles, boundary conditions, perform simulations, and obtain key result visualizations. This foundational skill set prepares you for more advanced modeling tasks throughout the course.

This lesson introduces the process of performing hydraulic calculations on a specific river section using HEC-RAS. You will learn how to start a new project, set up the project's geometry by defining river reaches and cross sections, and input vital data such as station coordinates and elevations.

The tutorial guides you through organizing the data structure by assigning section numbers correctly in upstream to downstream order and adding detailed roughness coefficients through Manning's values for the channel and banks. You will also discover how to efficiently transfer cross-section data with a practical Excel example provided with the lesson.

Once the geometric data is saved, the lesson explains how to use HEC-RAS's hydraulic design functions to calculate one of three key variables — slope, flow, or water surface elevation — based on inputs of the other two. This involves setting uniform flow conditions and interpreting calculation results graphically.

Key topics covered in this lecture:

• Creating a new project and saving it appropriately

• Editing geometric data: river reach and cross-section setup

• Assigning ascending section numbers upstream to downstream

• Using Excel to input cross-section station and elevation data

• Setting Manning's roughness coefficients for channel and banks

• Saving geometric data within HEC-RAS

• Running uniform flow hydraulic calculations and interpreting results

Practical value for hydraulic flood modeling:

• Build a foundational skill for preparing HEC-RAS models with correct geometry setup

• Understand how to input and edit detailed cross-sectional data accurately

• Learn to calculate unknown hydraulic variables using known parameters efficiently

• Apply calculation results to analyze flood behavior at specific river sections

By the end of this lesson, you will understand how to organize your project data, configure critical hydraulic parameters, and perform targeted calculations within HEC-RAS to assess river hydraulic conditions at specific sections, preparing you for more advanced modeling steps.

In this lecture, we focus on the critical topic of defining boundary conditions in HEC-RAS for steady state steady flow modeling. Boundary conditions are essential as they set the limits and behavior of the hydraulic model, whether it is a river, creek, or canal. This session builds on the previous project by exploring in detail how to accurately configure these parameters to reflect realistic flow scenarios within the model.

The lecture begins by guiding learners to open the existing project and highlighting the importance of organizing project files through the program setup, specifically by setting a default project folder. This practice simplifies file management and accessibility during modeling work.

Next, various types of boundary conditions available in HEC-RAS are explained. These include:

• Known Water Surface (Known WS)

• Critical Depth

• Normal Depth

• Rating Curve (Flow Curve)

Each option corresponds to different types of flow and water level information that can be supplied to the model depending on the available data and characteristics of the hydraulic system. Known WS is used when actual water level measurements from gauges are available. Critical depth is relevant mainly where flow control features, such as landfills or dams, exist. Normal depth is the most commonly used condition and relates to the energy slope inferred from the channel's longitudinal profile. The rating curve option allows entry of flow-height relationships obtained from measurement instruments.

The critical discussion on normal depth is particularly valuable, where it is presented as a function of the slope between two closest cross-sections at the upstream or downstream ends. This slope often needs to be estimated by extrapolating from the bed slope, with practical methods demonstrated, such as using profile plots in the software to precisely calculate the slope (DY over DX). This ensures more accurate representation of flow conditions.

The lecture then covers the practical rules for associating boundary conditions with flow regimes. For subcritical flows, conditions are typically applied downstream; for supercritical flows, they should be applied upstream; and mixed flows may require boundary conditions at both ends. These guidelines help learners understand how to configure the model according to the flow characteristics, improving the model's reliability.

Lastly, the lecture emphasizes the iterative process of data entry and model execution. After setting or modifying boundary conditions, it is crucial to apply the changes and rerun the steady flow analysis to observe the impacts. The comparison of models under supercritical and critical depth assumptions highlights how variations in boundary conditions affect flow profiles and energy balance warnings. Such feedback guides users in selecting the most appropriate modeling approach for their specific scenario.

Key Topics Covered

• Setting up the default project folder for file management

• Understanding and defining four types of boundary conditions in HEC-RAS

• Using Known Water Surface boundary conditions with measured data

• Applying Critical Depth conditions for flow control structures

• Calculating and using Normal Depth based on channel slope

• Entering flow and water height relationships via Rating Curves

• Interpreting flow regimes (subcritical, supercritical, mixed) to assign boundary conditions appropriately

• Techniques to measure slope using profile plots in HEC-RAS

• Iterative modeling process: applying changes and re-running steady flow analysis

• Evaluating model warnings and results to refine boundary condition selection

Practical Value in Hydraulic Analysis Using HEC-RAS

• Learn to accurately define model limits that critically influence simulation behavior

• Understand practical approaches to incorporate real-world measurement data into models

• Gain proficiency in selecting boundary conditions that reflect physical flow regimes

• Utilize software tools to calculate key hydraulic parameters like slope for normal depth

• Develop skills in troubleshooting model balance issues using flow regime knowledge

• Recognize the importance of iterative model adjustment for reliable hydraulic predictions

• Apply these boundary condition concepts for more precise flood and flow modeling results

By completing this lecture, learners will understand how to define and apply the various boundary conditions in HEC-RAS for steadystate flow scenarios, enabling them to build more accurate and stable hydraulic models adaptable to different flow regimes and real-world data inputs.

In this detailed lecture, learners are guided through the process of adding a bridge structure within the HEC-RAS software, a critical skill for modeling river hydraulics and flood scenarios where bridges influence flow behavior. Starting from loading a base project featuring a 100-meter river section, the lesson focuses on practical application, emphasizing not only how to insert a bridge but also on understanding the importance of correctly positioning cross sections near the bridge for accurate hydraulic representation.

The lecture explains that while geometry data often comes from external programs such as Civil3D, AutoCAD, or HEC-GeoRAS, it is important to know how to verify and modify bridge components directly inside HEC-RAS. This understanding ensures that users can correct or customize imported data for better model performance and realistic simulation results.

The workflow involves accessing the geometry editor to add a bridge culvert, the most common type of bridge structure in river cross sections. Learners are introduced to the bridge’s structural components, including the platform (deck), piers (columns), and stirrups (abutments), and learn how to configure each element with precise spatial and dimensional parameters. Attention is given to setting the platform width, height chords at both ends, and aligning the structure properly with upstream and downstream sections.

The tutorial highlights the importance of defining upstream and downstream sections close to the bridge—typically about 10 meters—to ensure the hydraulic simulation correctly represents flow conditions around the structure. Practical adjustments are made step-by-step, such as modifying pier widths and observing how these changes affect water surface elevations, demonstrating the sensitivity of flood levels to structural details.

Advanced editing options are covered, including the placement of columns with specific stationing, width parameters both upstream and downstream, and the addition of stirrups with triangular shapes on abutments. The lesson also reinforces good modeling practices by saving geometry and re-running simulations to visualize how the inclusion of a bridge alters flow behavior in the steady flow computations.

Finally, learners are encouraged to experiment by creating and modifying their own bridges within HEC-RAS to see firsthand how varying dimensions influence hydraulic results. This hands-on approach supports deeper understanding and skill development in modeling river infrastructure impacts on flow regimes.

Key topics covered in this lecture:

• Loading and preparing base project geometry for modification

• Bridge culvert definition and components in HEC-RAS

• Adding and positioning bridges between river cross sections

• Designing bridge platform dimensions and elevation chords

• Creating piers (columns) with station-specific location and widths

• Defining stirrups (abutments) and their geometric parameters

• Importance of upstream and downstream cross sections near the bridge

• Running steady flow simulations with bridges incorporated

• Analyzing flow behavior and water surface elevation changes due to bridge structures

• Best practices for saving geometry and verifying bridge modeling

Practical value for hydraulic modeling with HEC-RAS:

• Enables accurate inclusion of bridge structures affecting river hydraulics

• Improves model realism by proper bridge positioning and section placement

• Supports customization of bridge dimensions for site-specific conditions

• Empowers users to verify and adjust imported geometries within HEC-RAS

• Facilitates understanding of flow interactions with bridge infrastructure

• Helps predict changes in water surface elevation from structural modifications

• Develops skills for steady flow simulation setup including bridges

• Encourages hands-on practice for mastering bridge modeling workflows

By the end of this lecture, learners will be able to confidently add, customize, and simulate bridges in their HEC-RAS projects, enabling more precise hydraulic analyses of river sections impacted by infrastructure. This knowledge bridges theoretical concepts with practical modeling skills essential for flood risk assessment and river engineering applications.

This lecture delves into the powerful capabilities of the graphical cross section editor in HEC-RAS, a critical tool for customizing river and channel cross sections beyond basic data entry. Starting with a simple project containing two sections and a bridge, the lesson guides learners through accessing and manipulating the geometry visually rather than manually editing coordinates. This approach enhances precision and flexibility when working with complex river morphology.

You will learn how to navigate between different cross sections and modify their points graphically. The instructor demonstrates how to move vertices and river banks easily by dragging points, allowing for quick adjustments to channel shapes that reflect natural or engineered features accurately. Adding new points to the cross section is also covered, which supports refining the channel representation to better capture its hydraulics.

A major focus is placed on levees—important flood control structures modeled as barriers within the cross section. The lecture explains how levees can be incorporated graphically and through table options, detailing how to specify their location, elevation, and side (left or right bank). These levees prevent water from flowing into protected areas unless flood stages exceed their heights, an essential mechanism for realistic floodplain modeling.

The practical steps for placing levees, running analyses, and interpreting results are shown with real-time model recalculations. The visual feedback on flood boundaries and flow profiles helps learners understand levee effectiveness and flood impact in a simulated river environment. Furthermore, the instructor shares tips to manually adjust levees within HEC-RAS to fine-tune models where imported terrain may require correction.

Another important topic addressed is handling overly detailed cross sections that contain a large number of points. Excessive points (over 500) can cause modeling errors and software slowdowns. To resolve this, the lesson introduces the cross section points filter tool that reduces the number of points while maintaining the overall shape of the channel. This optimization technique improves model performance and prevents errors, making it an essential skill for managing large, complex datasets.

By the end of this lecture, you will confidently use the graphical editor to make precise modifications to cross sections, add and adjust levees effectively, and troubleshoot common issues related to point density. This hands-on approach empowers you to create accurate hydraulic models that reflect real river conditions and flood mitigation structures, improving the quality and reliability of your flood analyses.

Key topics covered in this lecture:

• Introduction to the graphical cross section editor interface

• Navigating and editing cross section points manually

• Moving river banks and vertices graphically

• Adding new points to refine cross section geometry

• Modeling levees as flood protection barriers

• Specifying levee location, height, and side

• Running hydraulic calculations with levees in place

• Visualizing flood profiles and water elevation changes

• Tips for correcting and tweaking levees within the software

• Using cross section point filtering to reduce data complexity

Practical value in hydraulic modeling and flood analysis:

• Enhances precision in cross section geometry editing without manual data entry

• Makes levee modeling accessible and intuitive for realistic floodplain simulations

• Improves flood risk assessment through accurate barrier representation

• Supports efficient model recalculation and scenario testing

• Helps prevent modeling errors caused by excessive cross section points

• Increases model stability and performance with point filtering

• Facilitates troubleshooting and fine-tuning of imported terrain data

• Enables users to confidently manage complex river and floodplain geometries

After completing this lesson, you will understand how to effectively use the graphical cross section editor to customize river channels and add levees in HEC-RAS. You will be able to apply these skills to improve model accuracy, run successful simulations, and address common challenges related to cross section data management in hydraulic flood modeling.

In this lecture, you will be introduced to Ras Mapper, an innovative feature integrated into HEC-RAS starting from version 5. Ras Mapper expands HEC-RAS’s capabilities by allowing users to conduct two-dimensional (2D) hydraulic modeling and simulate unsteady (non-permanent) flows with a spatially detailed approach. This represents a significant advancement over previous versions, which mainly focused on one-dimensional flow analyses.

The session begins with launching Ras Mapper and exploring its interface, which enables the loading and visualization of various geospatial layers including digitized geometries, result layers, and even online imagery such as satellite maps or Google Maps. This multi-layered display capability facilitates a better understanding of floodplain and terrain characteristics relevant to 2D hydraulic analyses.

Next, the workflow covers the creation of new projects within Ras Mapper, emphasizing the import of digital terrain models (DTM). Users will see how to select example datasets included in the HEC-RAS installation, which provide a practical base to build and experiment with 2D flood models. The lecture demonstrates defining a 2D flow area by outlining the area of interest on the terrain, effectively marking the spatial boundaries within which flow simulations will be conducted.

A critical step shown is the generation of a computational mesh based on the imported terrain data. The resolution of the mesh can be controlled (e.g., creating points every 10 meters), balancing detail and computation time. The lecture explains how to apply default and customized parameters such as Manning’s roughness coefficient for surface resistance, which greatly influence hydraulic simulation results.

Setting boundary conditions is essential for running accurate unsteady flow simulations. The instructor illustrates how to define upstream and downstream boundary arcs within the flow area and manually enter appropriate hydrologic data. For example, normal depth and slope are estimated using the digital terrain, and flow hydrographs are created with time-dependent flow values, representing flood wave progression through the modeled area.

Execution of the simulation involves iterative computations over defined time steps, which can require substantial processing time depending on mesh resolution and flow duration. Learners are encouraged to observe the flood’s temporal development through the visualization tools, including animations that show how floodwaters spread across the terrain during peak flow and recession periods.

Finally, the lecture highlights the practical usage of Ras Mapper for analyzing complex flood scenarios that vary over time and space unlike traditional 1D models. Although this introduction provides foundational knowledge, the feature’s full potential is reserved for more advanced HEC-RAS courses, where detailed hydrodynamic modeling of floods and inundation mapping can be explored extensively.

Key topics covered in this lecture:

• Introduction to Ras Mapper and its role in HEC-RAS 5+

• Launching Ras Mapper and interface overview

• Importing and visualizing digital terrain models and map layers

• Creating new projects and defining 2D flow areas

• Generating computational meshes with user-defined resolution

• Setting upstream and downstream boundary conditions for unsteady flow

• Constructing hydrographs for time-dependent flow inputs

• Running simulations with iterative computation and time stepping

• Visualizing flood depth progression and animations of flow dynamics

• Managing computation challenges and troubleshooting mesh recalculations

Practical value of Ras Mapper in hydraulic flood analysis:

• Enables spatially detailed 2D modeling of unsteady flood events

• Improves flood risk assessment through dynamic floodplain mapping

• Supports integration of real terrain and aerial imagery for contextual analyses

• Facilitates scenario testing with variable flow inputs and boundary conditions

• Provides a platform for advanced hydraulic modeling beyond 1D limitations

• Offers visualization tools that enhance interpretation of flood dynamics

• Allows users to generate high-resolution meshes tailored to study area and computational capacity

Upon completing this lecture, learners will understand the fundamentals of using Ras Mapper to set up, run, and analyze two-dimensional unsteady flow hydraulic models within HEC-RAS. You will be able to import terrain data, define modeling boundaries, configure time-varying flow conditions, execute simulations, and visualize flood extents over time, paving the way for more advanced flood modeling applications.

In this detailed lesson, learners are guided through the process of generating hydraulic model geometry using Ras Mapper, an integrated tool within HEC-RAS designed to facilitate spatial visualization and editing of river and terrain features. The session begins with instructions on setting up a new project, emphasizing the importance of correct projection systems for spatial data, although the demo model included simplifies this by pre-including projection information. Detailed guidance is provided on loading a digital terrain model (DTM), a crucial foundation for hydraulic modeling that represents the elevation data of the study area.

The lesson thoroughly explores the creation of geometry within the project, highlighting how to add new geometries and providing practical tips on naming conventions to keep projects organized and identifiable by location or feature type. A primary focus is placed on the essential components of hydraulic geometry modeling: rivers and cross sections. Learners see hands-on digitization of river centerlines, banks, and flow paths, with clear explanations on how to proceed systematically downstream and the importance of spatial orientation when drawing these features.

Particular care is given to the process of defining cross sections, underscoring the practice of digitizing from left to right, always facing downstream, to ensure consistency and accuracy in modeling. The lesson acknowledges the learning focus of the course rather than perfect precision at this stage, encouraging learners to grasp the workflow and tool functionalities.

The exercise continues by demonstrating how to save edits, load generated geometry, and visualize loaded layers including the terrain model, rivers, and cross sections—all fundamental to preparing a robust hydraulic analysis. Additional refinement tips are shared towards the end, such as using the graphical cross section editor to adjust banks and other features for better representation, emphasizing the need to verify model components against real-world conditions before final modeling.

The lesson wraps up by reinforcing the value of Ras Mapper as a powerful tool that eliminates dependencies on external GIS or CAD software for generating geometry, streamlining the workflow directly within HEC-RAS. Encouragement is given to learners to practice these skills to deepen their understanding and proficiency.

Key topics covered in this lecture:

• Project creation and naming conventions in Ras Mapper

• Loading and managing digital terrain models within HEC-RAS

• Principles and techniques for digitizing river centerlines, banks, and flow paths

• Establishing and editing cross sections with correct spatial orientation

• Using the graphical cross section editor for post-digitization refinements

• Saving and loading geometry data

• Verifying and validating geometry for hydraulic modeling

• Understanding the integration of geometry generation within Ras Mapper

Practical value within hydraulic modeling and flood analysis:

• Empowers users to independently create detailed river and terrain geometry without external GIS tools

• Provides foundational skills critical for building both 1D and 2D hydraulic models in HEC-RAS

• Introduces workflow best practices for accurate spatial data digitization

• Enables improved data management through informed naming and project organization

• Delivers practical techniques for terrain and hydraulic feature editing to enhance model fidelity

• Facilitates a clear understanding of the relationship between terrain data and hydraulic model inputs

• Strengthens confidence in using HEC-RAS geometry tools for flood simulation projects

By completing this lesson, learners will have a clear understanding of how to generate, edit, and manage geometry within Ras Mapper, enabling them to set up effective hydraulic models with confidence and accuracy for flood analysis.

This lesson focuses on effectively visualizing and analyzing the results within HEC-RAS after completing a hydraulic model. You will learn how to open existing projects, inspect cross sections, and adjust the display settings to better understand flow dynamics and water surface profiles.

The lecture guides you through the workflow of importing geometry data, running steady flow analyses, and using various visualization tools including cross section views, profile plots, rating curves, and 3D multiple cross section plots.

By interacting with the graphical interface, you will customize the display of key variables like water surface elevation, critical depth, energy grade, and velocity distributions. Exporting reports and graphical outputs such as PDFs is also covered to help document your models.

Key topics covered in this lecture:

• Opening and importing existing HEC-RAS projects

• Visualizing cross section data with customizable display options

• Modifying grid, lines, symbols, and plot styles for clarity

• Using profile plots and selecting variables to analyze

• Generating and interpreting rating curves

• Exploring 3D multiple cross section plots for visual analysis

• Exporting graphical outputs and detailed output tables

Practical value for hydraulic analysis:

• Interpret model output to assess flood behavior and water surface profiles

• Customize visualizations to identify critical flow conditions and subcritical/supercritical zones

• Generate visual reports compatible with documentation and presentation needs

• Manipulate detailed summary tables to support data-driven decision making

After this lesson, you will be able to effectively navigate HEC-RAS result visualization tools, customize your views for detailed hydraulic analysis, and export meaningful outputs for reporting or further study.