Example 6AElementary HEC-HMS Model

PurposeIllustrate the steps to create a functioning precipitation-runo model in HEC-HMS. The example is elementary in the sense that only a small set of HEC-HMS capabilities are employed Realistic parameter values are employed from public-domain references, but the example is fabricated for pedagogical simplicity.

Learning ObjectivesFamiliarize students with the HEC-HMS Graphical User Interface. Reinforce the concepts of Projects as a data-storage paradigm.Simulate the rainfall-runo response of a single sub-basin Texas watershed using:Initial loss and constant rate loss modelSCS Unit Hydrograph transformation modelUser-specied hyetograph.

Problem StatementSimulate the response of the Ash Creek watershed at Highland Road for a 5-year, 3-hour storm, under current development conditions. Treat the entire watershed as a single sub-basin.

Problem StatementWatershed OutletHighland Road and Ash Creek, Dallas, TX.Area is residential subdivisions, light industrial parks, and some open parkland.White Rock Lake is water body to the North-West

Precipitation EstimationPrecipitationEstimate 5-year, 3-hour storm depth using the DDF Atlas

Precipitation EstimationPrecipitationApproximate the storm temporal distribution using dimensionless hyetograph.

Loss Model EstimationRunoff Generation (Loss)Estimate the initial abstraction and constant rate loss using TxDOT 0-4193-7

Transformation Model EstimationUnit Hydrograph Timing ParametersExample will use the SCS DUH, but will parameterize assuming GUHAS regression is appropriate.

Physical PropertiesWatershed PropertiesAREA=6.92 mi2MCL=5.416 miMCS=0.005595CN=86R=0

Building The Model Data PreparationHEC-HMS will require us to construct, external to HMS the following:A Hyetograph (rainfall)Loss model parametersTransform model parametersIn this example will use Excel to build some input data required by the program.

Use the DDF atlas to find the 5-year, 3-hour storm depth for Dallas Texas.About 2.8 in.Rainfall Depth

Generate a HyetographDimensionless Hyetograph is parameterized to generate an input hyetograph that is 3 hours long and produces the 5-year depth.We wont actually use the graph, instead use the tabular values in the report.For this example, will use the median (50th percentile) curve0 3 hours0 2.8 inches

We wont actually use the graph, instead use the tabular values in the report.This column scales TIMEThis column scales DEPTH

Dimensional Hyetograph

Dimensional HyetographUse interpolation to generate uniformly spaced cumulative depths.HEC-HMS can handle irregular interval data, but requires use of DSSVue.Reasonable alternative is interpolation.This example will interpolate external to HEC-HMS, then import the results.

Input HyetographWe will use this column in HEC-HMS and specify a 5-minute rainfall time-series.

Data PreparationHEC-HMS will require us to construct, external to HMS the following:A Hyetograph (rainfall)Loss model parametersTransform model parametersIn this example will use Excel to build some input data required by the program.

Loss Model ParametersIaCl model in TxDOT 0-4193-7

Loss Model ParametersIaCl model in TxDOT 0-4193-7

Loss Model ParametersIaCl model in TxDOT 0-4193-7

Loss Model ParametersIaCl model in TxDOT 0-4193-7

Data PreparationHEC-HMS will require us to construct, external to HMS the following:A Hyetograph (rainfall)Loss model parametersTransform model parametersIn this example will use Excel to build some input data required by the program.

Unit Hydrograph ModelSCS Dimensionless Unit HydrographRelated to a gamma distribution with shape K=3.77HEC-HMS requires a time constant, TpFor this example, will assume 0-4193-4 method is sufficient

Unit Hydrograph ModelEstimate Tp

Unit Hydrograph ModelEstimate K

Unit Hydrograph ModelEstimate K

Unit Hydrograph ModelSCS Dimensionless Unit HydrographRelated to a gamma distribution with shape K=3.77For this exampleAssume that K=3.2 is close enough in shape to K=3.77 to use without modification.A later example will illustrate how to employ a user-specified hydrograph.

Data PreparationHEC-HMS will require us to construct, external to HMS the following:A Hyetograph (rainfall)Loss model parametersTransform model parametersNow ready to build the HEC-HMS model.

HEC-HMSStart the programCreate a projectProject is a directory where all data are stored for a particular model. Can share files between projects, but an advanced technique.

HEC-HMSStart the programChoose File and New to create a new project

Create ProjectName the ProjectSelect Default Units(Metric or U.S. Customary)Description (optional)

Create ProjectName of the ProjectNote that project was created. This area is where notes, warnings, and error messages are presented to analyst.

Create Basin ModelChoose components and will begin our modeling

Create Basin ModelChoose Basin Model Manager

Create Basin ModelChoose NewName the BasinDescription

Create Basin Model2) Sub Basin Creation Tool

Select, then put a sub-basin into the hydrologic elements area1) Select the Basin Name in the Component Manager WindowBasin Hydrologic Elements(Starts Empty we will populate)

Create Basin ModelDescription (optional)Sub-basin name

Basin Model Data Input2) Select the sub-basin1) Select cursor tool3) Input hydrological and physical parameters

When you change from defaults, program will Ask you are you sure? For the example, answeryes and proceed.

4) When done, select the Loss tab.

Basin Model Data Input1) Input hydrological and physical parametersUse values from 0-4193-7Use 0% IC; 0-4193-7 accounted for IC

2) When complete, select Transform tab.

Basin Model Data Input1) Input hydrological and physical parametersUse values from 0-4193-3Use the standard SCS-DUH.

2) When complete, select Components menu item

Create Rainfall InputChoose Time-series Data ManagerWill supply the hyetograph input as a time-series.

a) Create a raingageb) Assign a time-series to the gagec) Specify type (cumulative inches)d) Select a time intervale) Check the input

Create Rainfall Input a) Select New b) Name the gage c) Description (optional) d) Select CreateData Type == Precipitation Gages

Create Rainfall InputData entry here:Units == Cumulative InchesTime Interval == 5 minutes (this example)Select Time Series/Precipitation Gages/Gage Name

Create Rainfall InputSelect Time Window We will make a 3:15 -hour long input sequence.

Create Rainfall InputSelect Table we will cut-and-paste the time series from Excel

Create Rainfall InputSelect Table we will cut-and-paste the time series from Excel -- Cut and paste 00:05 to 03:10 from the spreadsheet.

-- The first value at 00:00 is hand-entered as 0.00

-- The last value at 03:15 is hand entered as 3.00

Create Rainfall InputSelect Table we will cut-and-paste the time series from Excel -- Cut and paste 00:05 to 03:00 from the spreadsheet.

-- The first value at 00:00 is hand-entered as 0.00

Create Rainfall InputVerify that plot looks like the dimensionless hyetographGraphs should have similar shapeTotal depth == 2.8 inchesDuration == 3.0 hours

Create Meterological ModelSelect meterological model manager

The meterological model manager links the raingage to the basin.

Create Meterological ModelSelect New Name the modelDescription (optional)Select Create

Create Meterological ModelSelect MetModel1Verify Specified HyetographSelect Basinsa) Basins we will link the subbasin to the time series

Create Meterological ModelSelect Yes in Include SubbasinSelect Specified Hyetograph

Create Meterological ModelSelect OneAndOnlyGageThis action links the gage name,Time-series, and the basin models.

Create Control SpecificationsClose to a working model!

Select Control Specifications

Create Control SpecificationsNew Name and DescriptionCreate

Create Control SpecificationsProvide simulation start and end dates/timeShould cover the rainfall input time, but can be longerTime step should be appropriate.

Create Simulation Create simulation run

Create Simulation Name the run (default is Run #)Choose next

Create Simulation Verify model selectionsChoose next

Create Simulation Verify model selectionsChoose next

Create Simulation Verify model selectionsChoose Finish

Run Simulation Run simulation from the compute menu item, or

The flaming water drop icon.

Run Simulation Successful run:

Run Simulation Right-Click on the sub-basin to obtain results

For this example choose : View results/Graph

View Results Hyetograph(Blue)Loss (Red)Hydrograph (Blue)Summary Table (Separate Window Query)Total Precip should agree

HEC-HMS Example Learning PointsHave some effort external to the softwareNeed to a-priori specify precipitation, unit hydrograph, lossNeed 4 components for a functioning modelBasinTime-SeriesMeteorological ModelControl Specifications

HEC-HMS ExampleLearn moreHEC HMS quick start guide (similar problem, more sub-basins)RemarksToo large to model in SWMM as a single catchment. (Can make it work, but hard to justify)More typical is to subdivide the watershed into parts and link with conduits; need some insight into flow patterns, etc.