This course explores rainfall-runoff modeling with HEC-HMS and HEC-RAS and is the fourth course in our pathway of HEC-RAS courses.

Participants will use RAS Mapper as a GIS tool to prepare terrain and spatial inputs, set up basin models in HEC-HMS, apply meteorological models, choose transform, loss, and routing methods, run HEC-RAS rain-on-grid simulations with direct precipitation, and compare and calibrate results using gage data. The course emphasizes the strengths and limitations of both programs and uses workshop datasets to compare modeling approaches.

Our HEC-RAS pathway of courses is as follows:

1.     Using HEC-RAS to Model Bridges, Culverts, and Floodplains

2.     Advanced 2D Modeling with HEC-RAS and RAS Mapper

3.     Advanced Hydraulic Structures in HEC-RAS

4.     Rainfall-Runoff Modeling with HEC-HMS and HEC-RAS (this course)

Participants should have basic hydrology knowledge and some familiarity with HEC-RAS or HEC-HMS. It is highly recommended that participants take the earlier courses in the HEC-RAS pathway before taking this course; however, it is not required.

• Engineers, hydrologists, floodplain managers, consultants, agency reviewers, planners, and technical staff who prepare, review, or use hydraulic models.
• Professionals who need to translate rainfall into runoff hydrographs for hydraulic models, watershed studies, floodplain analyses, stormwater planning, or infrastructure review.
• Consultants and technical professionals performing hydraulic studies or regulatory submittals.
• Government agency staff and planners responsible for flood risk assessment, permitting, or infrastructure review.
• All participants who have taken other HEC-RAS Courses in our HEC-RAS pathway of courses at UW-Madison

·       Use RAS Mapper to prepare terrain and spatial datasets for HEC-RAS and HEC-HMS workflows.

·       Develop a basin model in HEC-HMS using subbasins, reaches, junctions, reservoirs, and outlets.

·       Apply meteorological models and precipitation inputs in HEC-HMS.

·       Select appropriate loss, transform, baseflow, and routing methods for project goals and available data.

·       Apply direct precipitation in HEC-RAS for rain-on-grid modeling and evaluate model setup considerations.

·       Compare HEC-HMS hydrographs and HEC-RAS rain-on-grid results using common workshop datasets.

·       Calibrate and interpret rainfall-runoff results using stream gage, precipitation, and observed event data.

This course is offered online:

• Offered over 6 weeks, with pre-recorded content, exercises, and a 1.5 hour Live session each week.
• A recording will be made available of the live session for those who cannot attend.
• Participants should expect to spend 3-5 hours per week on the course.
• This format offers significant flexibility for working professionals and can accommodate a variety of schedules.

Online Course Schedule (Offered over 6 weeks)

• Week 1, Topic 1: RAS Mapper as a GIS Tool for Terrain and Spatial Preparation
• Week 2, Topic 2: Setting Up a Basin Model in HEC-HMS
• Week 3, Topic 3: Applying Meteorological Models in HEC-HMS
• Week 4, Topic 4: Transform, Loss, and Routing Methods in HEC-HMS
• Week 5, Topic 5: Direct Precipitation and HEC-RAS Rain-on-Grid Modeling
• Week 6, Topic 6: Comparing and Calibrating HEC-HMS and HEC-RAS Results

Topics covered over the 6 week course:

RAS Mapper as a GIS Tool for Terrain and Spatial Preparation

Preparing terrain and watershed data for hydrologic and hydraulic workflows

·       Terrain, projection, imagery, land cover, soils, stream networks, and gage datasets

·       Using RAS Mapper to organize, visualize, and prepare spatial inputs

·       Terrain processing concepts for HEC-RAS and HEC-HMS applications

·       Data quality, resolution, watershed boundaries, and coordinate system considerations

·       Workshop setup and overview of comparison datasets

Setting Up a Basin Model in HEC-HMS

Building the watershed representation

·       HEC-HMS project organization and basin model components

·       Subbasins, reaches, junctions, reservoirs, diversions, sources, sinks, and outlets

·       Parameterizing drainage areas, slopes, lengths, connectivity, and routing elements

·       Importing or entering physical basin data

·       Hands-on basin model setup exercise

Applying Meteorological Models in HEC-HMS

Translating precipitation data into model inputs

·       Meteorological model types and precipitation data sources

·       Design storms, frequency storms, observed events, gridded precipitation, and gage weighting

·       Temporal distribution, time step selection, and missing data considerations

·       Linking meteorologic models to basin models and control specifications

·       Reviewing precipitation inputs and storm event assumptions

Transform, Loss, and Routing Methods in HEC-HMS

Selecting methods that fit the watershed and data

·       Loss methods such as SCS Curve Number, Green-Ampt, deficit and constant, and initial and constant approaches

·       Transform methods such as SCS Unit Hydrograph, Clark Unit Hydrograph, ModClark, and Snyder

·       Baseflow and channel routing method options

·       Parameter estimation, sensitivity, and model limitations

·       Running HEC-HMS simulations and reviewing hydrographs

Direct Precipitation and HEC-RAS Rain-on-Grid Modeling

Applying rainfall directly to 2D hydraulic models

·       Conceptual differences between HEC-HMS hydrograph routing and HEC-RAS rain-on-grid modeling

·       Applying precipitation to 2D flow areas

·       Terrain, mesh, roughness, infiltration, and time step implications

·       Boundary conditions, initial conditions, and model stability considerations

·       Running rain-on-grid simulations and interpreting spatial results

Comparing and Calibrating HEC-HMS and HEC-RAS Results

Using observed data to evaluate and refine model performance

·       Comparing hydrographs, peak flow, runoff volume, timing, depths, and inundation patterns

·       Calibration with stream gage, precipitation, high water mark, and observed event data

·       Sensitivity analysis for loss, transform, routing, roughness, infiltration, and mesh assumptions

·       Communicating uncertainty and documenting modeling decisions

·       Final comparison exercise, questions and answers, and wrap-up

Krey Price

Krey Price is a civil engineer specializing in water resources. Krey is based in Perth, Australia, where he provides consulting and training services in flood modeling. Krey has a master’s degree in hydraulic and coastal engineering from the University of California at Berkeley. Krey’s thirty-year career has included modeling, design, and project management for international flood mitigation projects.