Overview

This workshop illustrates steps to develop a basic HEC-HMS debris yield model from scratch using existing field data.  This workshop focuses on developing a debris yield model quickly.  This is relevant for emergency response type situations where the modeler is expected to produce a rough estimate of accumulated sediment/debris yield based on given field data from the burned watershed. In this workshop, you will summarize the model parameters in the given field data set and choose appropriate input parameters for the debris yield simulation under the burned watershed. If you need more detailed information please refer to the User's manual.

Data acquisition requires field investigation to estimate required input parameters using GIS tools based on given data (rainfall data, topographic maps, Baer fire severity map, field soil sample, etc.)  Field data also requires collection soil sample to generate the gradation curve. However, this gradation curve was estimated based on published data set because a field soil sample was not available.

Debris Basin

Area (KM2)

Longest Flowpath Length (KM)

Basin Relief (M)

Relief Ratio (M/KM)

Burn Date

Burn %

Burned Area(KM2)

Rainfall Debris Yield Simulation Period
Brand DB2.62632.86997620.47018216.1939602 Sep 2002902.36367Forecasted Rainfall (Generated based on Childs_Canyon_Gage data for this workshop)16Mar2003, 00:00 - 16Mar2003, 04:00 


Gradation Curve 

Forecasted Rainfall Amounts (16 Mar 2003 00:00 - 16 Mar 2003 04:00)

Develop the Model

  1. Create a new HEC-HMS project with HEC-HMS version 4.10 or greater by selecting File | New. 
    1. Name the project Mountain_Fire_2002
    2. Set the proper project Location.
    3. Set the Default Unit System to Metric.
  2. Create a new basin model by selecting Components | Create Component | Basin Model 
    1. Name the basin model Brand_Canyon_LAEQ1
  3. Select the Basin Models folder to expand the Watershed Explorer. 
  4. Select Brand_Canyon_LAEQ1 Basin Model. 
  5. Click the subbasin creation tool icon  in the components toolbar.
  6. Click on the basin map to create a subbasin element and name the subbasin element Brand_Canyon.
  7. Switch to the sink creation tool icon  in the components toolbar.
  8. Click on the basin map to create a sink element and name the sink element Brand_DB.
  9. The elements should be placed as shown in the figure below.
  10. Connect the elements into a hydrologic network as shown in the figure below. Right click on Brand_Canyon subbasin element and select the Connect Downstream option. Use the mouse to identify the sink element Brand_DB that should be downstream. A connection line is drawn to show the elements are connected
  11. Select the Basin Models (Brand_Canyon_LAEQ1) and select Yes for the Sediment option in the Basin Model Tab as shown below.
  12. Updated sediment Density as show below as a mixture debris flow density by selection Sediment tab. This value was assumed based on the literature value range (1500-2200) as a debris mixture density.
  13. Select the subbasin element Brand_Canyon.
    1. Select the Subbasin Tab.
    2. Enter the Area (2.6263 Km2) and select None for all of methods.  Select LA Debris Method EQ1 for the Erosion Method as shown below.
  14. Select the Erosion Tab and populate initial parameters values based on the given data provided in the table above. Erosion parameters are described in the User's manual.
    1. A-T Factor: 1.0 (Default Value)
    2. Relief Ratio (M/KM): 216.19 (from Table above)
    3. Fire Factor Method: Pak & Lee Fire Factor (Select this option for this case)
    4. Date (DDMMMYYYY): 02Sep2002  (from Table above)
    5. Percent: 90  (from Table above)
    6. Flow Rate Thresholds (M3/S): 0.030 (Default Value)
    7. Exponent: 1 (Standard Value)
    8. Prepare a Gradation Curve based on the given data above
      1. click Components | Paired Data Manager
      2. select Data Type: Diameter-Percentage Function
      3. click New
      4. name the gradation curve Debris Flow Mixture
      5. click Create
      6. Select the newly added gradation curve Debris Flow Mixture
      7. Select Paired data tab
        1. Select Data Source: Manual Entry
        2. Select Unit: MM : %Finer
      8. Select Table Tab and Enter the values for the gradation curve as shown in below
    9. Go back to the Erosion Tab under the Brand_Canyon subbasin and select Gradation Curve Debris Flow Mixture.

  15. Create a New Meteorologic Model.
    1. Create a new precipitation gage. Go to the Components | Time-Series Data Manager option. Under Data Type, select Precipitation Gages.  In the manager window, press the New button.
    2. In the new gage window, change the default name to Forecasted Raingage. Press the Create button
    3. Set up data source by go to the Watershed Explorer and click on the new gage you just created. 
    4. In the Watershed Explorer, click + button on the Forecasted Rainfall gage to expand time window under the Forecasted Rainfall gage. In the Component Editor, change start date to 16Mar2003, the start time to 00:00, the end date to 16Mar2003, and the end time to 04:00
    5. Click on the Table Tab and enter the value for Precipitation as shown in below.
    6. Click on the Graph Tab in the Component Editor to see the data.
    7. Click on the Components | Meteorologic Model Manager.  Press the New button to create a new Meteorologic Model and name it Forecasted Rainfall.
       
    8. Click on the new Meteorologic Model Forecasted Rainfall you just created and populate the Meteorologic Model parameters as shown below.
    9. Select to the Basins tab and select Yes in the Include Subbasins column.
    10. In the Specified Hyetograph node, select the newly-created precipitation gage Forecasted Rainfall in the Gage column.
  16. Create a New Control Specifications.
    1. Click on the Components | Control Specifications Manager. Press the New button to create a new Control Specifications.
    2. Change the name to 16Mar2003 and enter a description of Forecasted Rainfall. Press the Create button.
    3. In the Watershed Explorer, click on the control specifications you just created. Enter Start Date 16Mar2003 00:00 and End Date 16Mar2003 04:00. Select 15 Minutes for the time interval as shown in the figure below.

  17. Creating and Computing a Simulation Run.
    1. Click on the Compute menu and select the Create Compute | Simulation Run option. A wizard window will open to guide you in creating a new simulation run. In the first step enter name 16May2003_LAEQ1.
    2. In second step, choose the Brand_Canyon_LAEQ1 basin model. In third step, choose the Forecasted Rainfall meteorologic model. In Step 4, choose the 16Mar2003 control specifications. Press the Finish button to complete the process of creating a simulation run.
    3. A simulation run must be selected before it can be computed. The tool bar includes a selection list that shows all of the simulation runs that have been created in the project. Click on the selection list and choose RUN: 16May2003_LAEQ1. Once a simulation run has been selected, click on the Compute button  immediately to the right of the selection list to perform the compute. The tool bar button has an icon of a raindrop whenever a simulation run is selected. A compute progress window will open to show the advancement of the simulation. The simulation may abort if errors are encountered. If this happens, read the messages and fix any problems; then compute the simulation run again. Close the progress window when the run computes successfully.

  18. Viewing Debris Yield Simulation Results.
    1. Select the Result Tab and select Sediment node under the Brand_Canyon sunbasin element.
    2. Click each sediment results (Sediment Load (Total Sediment including all grain sizes), Sediment Load - Silt,  Sediment Load - Sand, Sediment Load - Gravel, Sediment Concentration).

      Question 1: Why is the zero value for the Sediment Load for Clay?

      Because clay was not included in the gradation curve. In the soil sample around the debris basin, there is no clay material.

    3. Check the accumulated total debris yield by Tonne.
      1. Go to your project folder
      2. Open the output DSS file (16May2003_LAEQ1.dss) for LA EQ1 method
      3. Double-Click SEDIMENT LOAD for total sediment load as shown below
      4. Click on Tools | Math Functions... and Click on Statistics Tab then read Accumulated Amount.

        Question 2: What is the estimated total sediment load with the forecasted rainfall amount on 16 Mar 2003?

        36,920 TONNE

  19. If you are interested in other debris yield methods (MSDPM, USGS-EA, and USGS-LT), please follow the above steps for each method. With these additional tasks, you can see differences among four different methods as shown below and determine the best debris yield simulation result.

Download the final model files here - Quick Debris Yield Workshop - Existing Model_Final.7z