1. HEC-HMS The Hydrologic Engineering Center’s Hydrologic Modeling System (HMS)

2. Summary of Topics - HEC-HMS
Premier Hydrologic Model Today (HEC)
Performs RF-RO Calculations for Watersheds
Basic Input and Output Options
Precipitation Options
Unit Hydrograph Options
Flood Routing Option
Creating and Viewing Results and Graphs

3. Execution of HEC-HMS Running actual projects Calibration to gage data
Castro Valley case study
Keegans example
Linkage with GIS/NEXRAD data (HEC Geo-HMS)

4. The Hydrologic Cycle

5. Uses of the HEC Program
Models the rainfall-runoff process in a watershed
based on watershed physiographic data
Offers a variety of modeling options in order to compute UH for basin areas.
Offers a variety of options for flood routing along streams.
Capable of estimating parameters for calibration of each basin based on comparison of computed data to observed data

6. HEC-1 Program History HEC-1 - History of Model Development
Separate Programs: 1967 by Leo R. Beard
Major Revision and Unification: 1973
Second Major Revision: 1981 (Dam Breach, Kinematic Wave)
PC Versions: 1984 (partial), 1988 (full)

7. HEC-1/HMS Program History
Current Versions: 1991, 1998
1991 Version Provides Extended Memory Support
1998 Version 4.1 is Final Release
HEC “NexGen” Project Begins 1990
(RAS, HMS, FDA)
HEC-HMS - New GUI and Updates
First Release April 1998
Version 1.1 Released April 1999
Current Version 2.0.3

8. HEC-HMS Background Purpose of HEC-HMS Importance of HEC-HMS
Improved User Interface, Graphics, and Reporting
Improved Hydrologic Computations
Integration of Related Hydrologic Capabilities
Importance of HEC-HMS
Foundation for Future Hydrologic Software
Replacement for HEC-1

9. Improvements over HEC-1
Ease of Use
projects divided into three components
user can run projects with different parameters instead of creating new projects
hydrologic data stored as DSS files
capable of handling NEXRAD-rainfall data and gridded precipitation
Converts HEC-1 files into HMS files

10. HEC-HMS Availability Available Through HEC Vendors
Available at HEC Web Site:
“Public Domain” Program
No Copyright on Software
No Copyright on HEC Documentation
Special Training Available

14. Program Organization Main project screen
Connects to all data and information through menus

15. Using HEC-HMS Three components
Basin model - contains the elements of the basin, their connectivity, and runoff parameters
Meteorologic Model - contains the rainfall and evapotranspiration data
Control Specifications - contains the start/stop timing and calculation intervals for the run

16. Project Definition
May contain several basin models, meteorologic models, and control specifications
User can select a variety of combinations of the three models in order to see the effects of changing parameters on one subbasin

17. Basin Model Basin Model Based on Graphical User Interface (GUI)
Click on elements from left and drag into basin area
Can import map files from GIS programs to use as background
Actual locations of elements do not matter, just connectivity and runoff parameters

18. Basin Model Elements
subbasins- contains data for subbasins (losses, UH transform, and baseflow)
reaches- connects elements together and contains flood routing data
junctions- connection point between elements
reservoirs- stores runoff and releases runoff at a specified rate (storage-discharge relation)

19. Basin Model Elements sinks- has an inflow but no outflow
sources- has an outflow but no inflow
diversions- diverts a specified amount of runoff to an element based on a rating curve - used for detention storage elements or overflows

20. Basin Model Parameters
Loss rate, UH transform, and baseflow methods

21. Abstractions (Losses)
Interception Storage
Depression Storage
Surface Storage
Evaporation
Infiltration
Interflow
Groundwater and Base Flow

22. Loss Rate methods Green & Ampt Initial & constant SCS curve no.
Gridded SCS curve no.
Deficit/Constant
No loss rate

23. Initial and Uniform Loss Computation
Initial Loss Applied at Beginning of Storm
Estimated from Previous or SCS data
Sand: inches; Clay: inches
Uniform Loss Applied Throughout Storm
Also Estimated From Previous Studies or SCS Data
Sand: in/hr; Clay in/hr

24. HEC-HMS Loss Entry Window

25. Rainfall/Runoff Transformation
Unit Hydrograph
Distributed Runoff
Grid-Based Transformation
Methods:
Clark
Snyder
SCS
Input Ordinates
ModClark
Kinematic Wave

26. Unit Hydrograph Definition: Duration of UH:
Sub-Basin Surface Outflow Due to Unit (1-in) Rainfall Excess Applied Uniformly Over a Sub-Basin in a Specified Time Duration
Duration of UH:
HEC-HMS Sets Duration Equal to Computation Interval

27. Synthetic Unit Hydrographs
Computed from Basin Characteristics
HEC- HMS Synthetic Unit Hydrographs
SCS Dimensionless Unit graph
Clark Unit Hydrograph (TC & R)
Snyder Unit Hydrograph
User-Defined Input Unit Hydrograph
ModClark Unit Hydrograph

28. Clark Unit Hydrograph Computation

29. Estimating Time of Concentration for Clark Unit Hydrograph
Hydraulic Analysis Method
Compute Travel Time in Open Channels and Storm Sewers based on Flow Velocities
Compute Reservoir Travel Time from Wave Velocity
Overland Flow Equations
Kerby Method
Kirpich Method
Overton & Meadows
SCS TR-55 Method for Shallow Concentrated Flow

30. Baseflow Options recession constant monthly linear reservoir
no baseflow

31. Stream Flow Routing
Simulates Movement of Flood Wave Through Stream Reach
Accounts for Storage and Flow Resistance
Allows modeling of a watershed with sub-basins

32. Reach Routing Flood routing methods: Simple Lag Modified Puls
Muskingum
Muskingum Cunge
Kinematic Wave

33. HEC-HMS Methods for Stream Flow Routing
Hydraulic Methods - Uses partial form of St Venant Equations
Kinematic Wave Method
Muskingum-Cunge Method
Hydrologic Methods
Muskingum Method
Storage Method (Modified Puls)
Lag Method

34. Effects of Stream Flow Routing
Avg Inflow - Avg Outflow = dS/dt
Storage S
Inflow
Outflow Dt

35. Modified Puls (Storage) Stream Flow Routing Method
Storage-Indication Relationship:
I - Q = (dS/dt)
Averaging at two points in time: 1 and 2
I1 + I2 + (2S1/Dt - Q1)= (2S2/Dt + Q2)

36. HEC-HMS Stream Flow Routing Data Window

37. Storage-Discharge Relationships

38. Stream Flow Diversions
Diversion Identification
Maximum Volume of Diversion (Optional)
Maximum Rate of Diversion (Optional)
Diversion Rating Table
Stream Flow Rates Upstream of Diversion
Corresponding Diversion Rates

39. Stream Flow Diversions
Flow is allowed to move from one channel to another via a side weir or flow across a low divide
Weir
Diverted Q
Flow increases until a fixed level and then a
flow diversion table determines rate through
the weir or across the divide

40. Reservoir Routing Developed Outside HEC-HMS
Storage Specification Alternatives:
Storage versus Discharge
Storage versus Elevation
Surface Area versus Elevation
Discharge Specification Alternatives:
Spillways, Low-Level Outlets, Pumps
Dam Safety: Embankment Overflow, Dam Breach

41. Reservoirs Pond storage with outflow pipe Orifice flow Weir flows
Inflow and Outflow

42. Reservoir Data Input Initial Conditions to Be Considered
Inflow = Outflow
Initial Storage Values
Initial Outflow
Initial Elevation
Elevation Data Relates to Both Storage/Area and Discharge
HEC-1 Routing Routines with Initial Conditions and Elevation Data can be Imported as Reservoir Elements

43. Reservoir Data Input Window

44. Meteorologic Model Meteorologic Model Evapotranspiration-ET
Precipitation
user hyetograph
user gage weighting
inverse-distance gage weighting
gridded precipitation
frequency storm
standard project storm - Eastern U.S.
Evapotranspiration-ET
monthly average,
no evapotranspiration

45. Precipitation Historical Rainfall Data Design Storms Recording Gages
Non-Recording Rainfall Gages
Design Storms
Hypothetical Frequency Storms
Corps Standard Project Storm
Probable Maximum Precipitation

46. Gage Data Gage Data (from project definition screen)
Precipitation gages- precipitation data for use with meteorologic models
Stream gages- observed level data to compare computed and actual results

47. Precipitation: Gridded Weather Radar Data
Data from National Weather Service
NexRAD program, Doppler Radar
Data must be manipulated and stored in DSS file format
Grids are HRAP (NWS) or SHG (HEC)
HRAP uses spherical projections and generalized earth radius values
SHG uses Albers Equal Area projections
Grids cover about 1 square kilometer
Historical raw data may not be archived

48. Sources of Rainfall Intensity-Duration-Frequency (IDF)
East of 105th Meridian (Denver)
NWS HYDRO-5 (5 minutes to 60 minutes)
NWS TP-40 (2 hours to 24 hours)
NWS TP-49 (2 days to 10 days)
West of 105th Meridian
NOAA Atlas 2 (Separate Volumes for Each State)

49. Input and Output Files
project-name.HMS: List of models, descriptions and project default method options
basin-model-name.BASIN: Basin model data, including connectivity information
precipitation-model-name.PRECIP: Precipitation model data
control-specifications- name.CONTROL: Control specifications
run-name.LOG: Messages generated during execution of run
project-name.RUN: List of runs, including most recent execution time

50. Input and Output Files
project-name.DSS: DSS file containing basin model data such as computed hydrographs and storage discharge relationships
project-name.DSC: List of files contained in DSS file
project-name.OUT: Log of operations for the DSS file
project-name.MAP: Coordinate point file for subbasin boundaries and channel location
project-name.GAGE: Listing of gages available for use in the project
HMStemp.TMP: Echo listing of imported HEC-1 model

51. Data Storage System (DSS)
Multiple time series or relational data sets
Each data set or record has a unique pathname/Castro Valley/Fire Dept/PRECIP-INC/16Jan197/10min/Obs/
Pathnames Consist of Parts A through F
Part A: General name, project name
Part B: Specific name, or control point
Part C: Data type (PRECIP-INC, PRECIP-CUM, FLOW, STORAGE, etc.)
Part D: Start Date
Part E: Time interval
Part F: User specified

52. The HEC-HMS “Options” Precipitation Option (6 available)
Loss Computation (5 available)
Runoff Transform Computation (6 available)
Routing Computation (7 available)
Over 6 x 5 x 6 x 7 = 1,260 Combinations
Subbasin
routing reach

53. Control Specifications
Control Specifications - Start/Stop/Time Interval

54. Running a project User selects the 1. Basin model
2. Meteorologic model
3. Control ID for the HMS run

55. Viewing Results
To view the results: right-click on any basin element, results will be for that point
Display of results:
hydrograph- graphs outflow vs. time
summary table- gives the peak flow and time of peak
time-series table- tabular form of outflow vs. time
Comparing computed and actual results: plot observed data on the same hydrograph to by selecting a discharge gage for an element

56. Viewing Results
hydrograph

57. HEC-HMS Output Tables Hyetograph Plots Sub-Basin Hydrograph Plots
Summary
Detailed (Time Series)
Hyetograph Plots
Sub-Basin Hydrograph Plots
Routed Hydrograph Plots
Combined Hydrograph Plots
Recorded Hydrographs - comparison

58. Viewing Results
Summary table
Time series table

59. HEC-HMS Output Sub-Basin Plots Runoff Hydrograph Hyetograph
Abstractions
Base Flow

60. HEC-HMS Output Junction Plots Tributary Hydrographs
Combined Hydrograph
Recorded Hydrograph

61. Purpose of Calibration
Can Compute Sub-Basin Parameters
Loss Function Parameters
Unit Hydrograph Parameters
Can Compute Stream Flow Routing Parameters
Requires Gage Records

62. FINALLY - information on HEC-HMS
istrib/hec-hms/hechmsprogram.html
(the user’s manual can be downloaded from this site)
Electronic_Documents
Available on the laboratory computers