ETL 1110-2-367
31 Mar 95
Table E-1
Interior Unit Hydrograph Parameters
Designated
Runoff
SCS
Interior
Interior
Area
Coefficient
T(LAG)
Location
Basin*
(sq mi)
(percent)
(HR)
Fishpot
FPI
0.08
85
0.11
Highway 141
HYW & HYW1
0.05
90
0.17
Highway 141
HYW1
0.02
95
0.06
with Outlet Closed
Glass Plant
GPT
0.37
85
0.31
Simpson Lake
SIM
0.11
85
0.13
Grand Glaize
GG1
0.09
85
0.11
*From Figure E-1
b.
Precipitation. Both hypothetical and continuous
hydrographs. The initial CSA analysis used a 10-min time-step
and each 1 hr of rainfall data was subdivided into 10-min
precipitation data would be necessary for the analysis.
increments.
(1)
Hypothetical storm time series were developed from
c.
Subarea runoff parameters. SCS unit hydrographs
the appropriate National Weather Service publications with a
10-minute time interval used, due to the short concentration
and simple runoff coefficients were used to generate interior
times of the interior basins. The 50- through 0.2-percent chance
runoff hydrographs based on expected future conditions.
exceedance hypothetical storms were generated.
Adopted values are shown in Table E-1.
d.
Exterior river stage. Long record stage and discharge
(2)
Because of the short duration of flooding for both
the tributary and the interior streams, time increments less than
information was available for the Meramec at the Eureka gauge,
24 hrs were needed for the CSA. Hourly precipitation records
located at River Mile 34.1, beginning in 1922. Daily stage data
were available at the St. Louis, Missouri, rainfall station from
for the period October 1948 through September 1988 was
01 October 1948 to 30 September 1988. This precipitation
assembled and transferred 12 to 14 miles downstream to
data stream could be readily transferred to the Valley Park site
simulate exterior river stages at each Valley Park outlet site.
for use with the CSA portion. Because of the short time of
Transfer relationships between the Eureka gauge and each outlet
concentration of the interior unit hydrographs, it was initially felt
site were developed through water surface profile analysis and
that a 1-hr duration was too long to accurately define the interior
are shown in Table E-2.
Table E-2
Eureka Gauge Transfer Curves
Eureka Gauge
Fishpot Creek
Glass Plant
Grand Glaize Creek
Elevation
Elevation**
Elevation
Elevation***
(NGVD)*
(NGVD)
(NGVD)
(NGVD)
429.09
415.52
415.14
413.54
435.89
421.43
420.97
419.10
440.64
424.73
424.19
422.18
444.73
429.30
427.87
425.75
446.55
431.69
430.55
428.38
447.23
432.66
431.76
429.63
448.29
434.07
433.17
430.97
452.99
440.95
439.09
436.83
456.36
444.12
442.70
440.73
* National Geodetic Vertical Datum.
** Also used for Highway 141 subarea analysis.
*** Also for the Simpson Lake subarea analysis.
E-2
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