HEC HMS Part One Tutorial

Tutorial on HEC-HMS: Hydrologic Engineering Center Hydrologic Modelling System

Introduction: HEC-HMS, developed by the U.S. Army Corps of Engineers, is a robust software for hydraulic modeling of river and floodplain systems. In this tutorial, we’ll cover the step-by-step process of setting up a project, defining basin components, importing GIS data, and performing a simulation run. The primary objective is to equip users with the foundational knowledge needed to analyze river systems and derive critical information for dam break analysis.

Step 1: Setting Up a New Project

  1. Open HEC-HMS and navigate to File -> New to initiate a new project.
  2. Provide a descriptive name and project details, select metric units, and designate a directory for the project. Confirm by clicking OK.
    In the left side panel, you can see a folder displayed under project name

Step 2: Creating Basin Model Components

  1. Goto Components Menu
  2. Proceed to Components -> Create Component -> Basin Model.
  3. Similarly Components -> Create Component -> Terrain data
  4. Input a name and description for the basin model and terrain data and click OK.
  5. Load terrain data by importing a shapefile (GIS raster file) for the Trishuli basin.

Step 3: Setting Terrain Data Coordinate System

  1. In Basin Models -> Basin 1 -> Components, select Terrain Data -> Terrain 1.
  2. Access Terrain 1 inside the Terrain Data folder.
  3. Specify the coordinate system parameters such as UTM type, UTM Zone (e.g., 45 N for Trishuli basin in Nepal), and datum (WGS 84).
    You will be seeing streams and features in map window

Step 4: GIS Preprocessing

  1. Execute GIS -> Preprocess Sinks for sink preprocessing.
  2. Conduct drainage preprocessing by navigating to GIS -> Preprocess Drainage.
  3. Identify streams through GIS -> Identify Streams and define the area to identify streams accurately.
    The smaller the area, the accurate the results but takes long processing time and inputs for areas

Step 5: Map Layers and Stream Identification

  1. View map layers by going to View -> Map Layers and selectively display identified streams for clarity.
  2. Locate a Hydrological station using GIS and Google Earth.
  3. Load the raster file which contains location of station from Add menu in Map Layers.
    In our case, Export_output will be loaded and we can see square demarcation of the point

Step 6: Break Point Creation and Delineation

  1. Zoom in on identified streams, use the Break Point Creation Tool to select a point, and create a break point.
  2. Proceed to GIS -> Delineate Elements Options to delineate subbasins, reaches, and junctions.
    To Break the point, we will be selecting a point in the river network, just near the location of station
    Remember to give name of Subbasin, Reach, junctions

Step 7: Merging Subbasins

  1. Merge subbasins that share the same flow points by selecting them and accessing GIS -> Merge Elements.
    We are merging subbasins so that we have smaller number of sub areas to process data

Step 8: Adding Time Series Data

  1. Introduce precipitation and discharge data by creating components in Components -> Create Component -> Time Series Data.
  2. Add a Meteorologic Model in a similar manner.
    Gages are created with proper Data type. In the left pane, access the sub folders named Precipitation/ Discharge Gages. In the components submenu, fill the required information such as Data Source, Units, Time Interval and other information such as start and end date of records.

Step 9: Specifying Hyetograph and Adding Controls

  1. Specify hyetograph using meteorologic models and set observed flow to the gage.
    After Fixing dates, we can enter data. Go to Basin models-> Select Sink -> set observed flow to gage 1.
  2. Incorporate controls via Components -> Create Component -> Control Specifications, defining parameters, start and end dates, and time intervals.

Step 10: Parameterization and Simulation

  1. Go to Parameters and set various parameters like canopy, surface, loss, transform, baseflow, snow, evapotranspiration, and routing.
  2. Enter data for each parameter and click Apply.
  3. Access Compute -> Create Compute -> Simulation Run, name the simulation, select basin, meteorologic model, and control, and finish setup.
  4. Execute the simulation by right-clicking on the simulation run in Compute -> Simulation Runs.

Step 11: Analyzing Results

  1. After a successful run, explore results in the Results section in the left pane.
  2. Analyze peak discharge, hydrographs, and other critical information obtained from the simulation results.

Significance of Results: After Processing in Hec HMS, the output results such as discharge over the period of time can be used to model the hydropower generation.