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Table Of Contents
Calculating Routing Values for Detention Basins
137
Calculating Routing Values for Detention Basins
Use the Storage Indication Method command to perform routing through a
detention pond or other water-storage facility. This command uses a post-
development hydrograph, stage-storage curve, and stage-discharge curve (as well
as an optional pre-development hydrograph for viewing in the multiple
hydrographs plot) to route runoff.
To create the required input files for using the Storage Indication Method, you
can use the TR-55 Graphical and Tabular runoff commands, the Rational
Method command, the Stage-Storage Curve command, and the Outflow
Editor ä By Pond command. Or, you can create the files manually.
Storage Indication Method Formula
The following Storage Indication Method formula is used for the routing
calculations:
SO tSO t II t
22 11 12
22 2  (/) [ (/)][( )/ ]'''
,
where:
S
2
+ (O
2
/ 2) 't = Storage characteristic at peak outflow (m
3
)
S
1
= Storage volume at time, t1 (m
3
)
O
1
= Outflow rate at time, t1 (cms)
't = Routing time period (hrs)
I
1
= Inflow rate at time, t1 (cms)
I
2
= Inflow rate at time, t2 (cms)