example 4 hec-hms simulation adding a detention pond at the outlet
TRANSCRIPT
Example 4
HEC-HMS Simulation
Adding a detention pond at the outlet
Purpose
• Illustrate data preparation and entry to model storage devices in HEC-HMS– Uses Example 3B as basis.
Learning Objectives
• Learn how to select canopy and depression storage abstractions.– Will use to examine effects
• Learn how to prepare storage-discharge tables.– Use Excel and typical hydraulics considerations to
build the table.
• Learn how to import the storage-discharge table into HEC-HMS– Paired-Data manager
Problem Statement
• Simulate the response of the Ash Creek watershed at Highland Road for 20 May 1978 historical conditions.– Use Example 3B as the base “model”– Use Example 3B output hydrograph as a
comparison hydrograph to examine effect of different abstractions on simulation
– Treat the entire watershed as a single sub-basin.
7 1 2 0 0 0 . 0 0 7 1 4 0 0 0 .0 0 7 1 6 0 0 0 .0 0 7 1 8 0 0 0 .0 0 7 2 0 0 0 0 . 0 0 7 2 2 0 0 0 . 0 0
3 6 2 6 0 0 0 .0 0
3 6 2 8 0 0 0 .0 0
3 6 3 0 0 0 0 .0 0
3 6 3 2 0 0 0 .0 0
3 6 3 4 0 0 0 .0 0
3 6 3 6 0 0 0 .0 0
3 6 3 8 0 0 0 .0 0
Background and Data• Watershed Outlet
– Highland 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
Physical Properties
• Watershed Properties– AREA=6.92 mi2– MCL=5.416 mi– MCS=0.005595– CN=86– R=0
7 1 2 0 0 0 . 0 0 7 1 4 0 0 0 .0 0 7 1 6 0 0 0 .0 0 7 1 8 0 0 0 .0 0 7 2 0 0 0 0 . 0 0 7 2 2 0 0 0 . 0 0
3 6 2 6 0 0 0 .0 0
3 6 2 8 0 0 0 .0 0
3 6 3 0 0 0 0 .0 0
3 6 3 2 0 0 0 .0 0
3 6 3 4 0 0 0 .0 0
3 6 3 6 0 0 0 .0 0
3 6 3 8 0 0 0 .0 0
Loss Model: Green-Ampt
• Parameter estimation– Initial water content. 0.187– Saturated water content: 0.464– Saturated hydraulic conductivity: 0.04 in/hr– Soil suction: 8.27 inches
Preparing Example 4
• “Clone” Example 3B and rename the project.– Select path– “Save-As”
Example 4• Run Example 4
– Export the simulation hydrograph to a file.– Re-import that file as a discharge gage.– We will use this hydrograph to examine effect of
abstraction changes.
• Will use skills developed in Example 3– External hydrograph import
• Develop new skill – exporting results
Prepare a Base-Case
• Run Example 4– Export the simulation hydrograph
to a file.
Export/Import Base Case
• Run Example 4– Import the result hydrograph to a
discharge gage.
Verify Import
• Re-Run Example 4– Set the result
hydrograph as the “observation” discharge gage.
– Observe “perfect” fit• Diagnostic in practical
models, perfect fits mean analyst chose wrong time series.
Canopy Abstraction
• Set canopy abstraction to some non-zero value.– What do we expect
discharge to do?
Canopy Abstraction
• Set canopy abstraction to some non-zero value.– What do we expect
discharge to do?• Storing up to ½ inch of
precipitation – anticipate that peak is reduced and a loss of early runoff.
Canopy Abstraction
• Set canopy abstraction to some non-zero value.– What do we expect
discharge to do?• Storing up to ½ inch of
precipitation – anticipate that peak is reduced and a loss of early runoff
• Run the new model and examine results
Depression Abstraction
• Similar procedure and data-entry items. – What do we expect
discharge to do?• Storing even more
precipitation, anticipate further reduction in peak.
– Run the new model and examine results
Reservoir Storage
• Now will return to more reasonable canopy and depression values– Canopy = 0.05 in– Depression = 0.25 in
• Will use as a basis before adding a reservoir element
Reservoir Storage
• Reservoir element– Locate on the basin
• Use toolbars in HEC-HMS
– Identify connection• Use connections in HEC-HMS
– Specify a storage-discharge relation• Build table externally (in Excel) then import information into
HEC-HMS
Example 4
• Reservoir element– Locate on the basin
• Use toolbars in HEC-HMS
Reservoir Storage
• Connections in HEC-HMS– Hydrologic/Hydraulic Elements are “connected” by
assigning to an element its downstream receiving element.
• Rainfall thus connects “downstream” to a sub-basin.
• In this example, the sub-basin will drain “downstream” to the reservoir
• The reservoir will then drain “downstream” to our outlet of interest (i.e. its output is the outlet)
Reservoir Storage
• Reservoir element– Identify the reservoir as
“downstream” of the sub-basin– In the sub-basin editor, we select
the reservoir as the downstream element
Reservoir Storage• Reservoir element
– Identify the reservoir as “downstream” of the sub-basin
– In the sub-basin editor, we select the reservoir as the downstream element
– If successful, then the connection is shown on the GUI
Reservoir Storage• Reservoir element
– Need to build the storage-discharge table– External to HMS – Analyze the reservoir hydraulics– This example, pretend an 8-foot deep
detention basin fit into the outlet somehow
Flow from Sub-Basin
Reservoir Storage
• Reservoir element– Analyze the reservoir
hydraulics
storage discharge
Reservoir Storage
• Storage-Discharge is entered in the “Paired Data “ structure– Components– Paired Data– New
Example 4
• Storage-Discharge Table by cut-paste from the worksheet– Need storage in Acre-
Feet
Reservoir Storage
• Run the model– Turned off the
canopy and depression storage so can compare effect of reservoir.
Reservoir Storage
• What if Reservoir is increased to 16X larger – about 0.5% of entire drainage area?– Notice the shifting in peak
location and magnitude
• Changed:– Multiplied the storage by
16.– Used the watershed outlet
as the source for reference curve
HEC-HMS Example 4
• Learning Points– Copy entire projects to keep different models
organized.– Canopy and Depression Storage are
abstractions – impact the excess precipitation.– Reservoir Storage attenuates the runoff
signal, and if sufficient delays peak arrival.• Stream routing will look similar to reservoir
behavior, parameterization is different.
HEC-HMS Example 4
• Learning Points– Used external analysis to build the storage-
discharge table• Simplified hydraulics to account for weir and orifice
flow.• Excel to produce the STORAGE-DISCHARGE
table.
– Paired Data manager for HMS table• Imported the Excel table into the Storage-
Discharge table in HMS
HEC-HMS Example 4
• Learning Points– Used output time series to build comparison
hydrographs to examine effect of changes• Use of a hand-written simulation log and some
forethought could allow multiple comparisons in a single project directory – file count could get large, naming convention would be important.
HEC-HMS Example 4
• Learn more– HEC HMS user manual– FHWA-NHI-02-001 Highway Hydrology
• Next module– Routing