HYDROLOGY
The existing and proposed waterway openings are located approximately 70’ up stream of the
confluence of Pucketa and The Unnamed Tributary to Pucketa Creek. The Unnamed Tributary,
which flows through the waterway opening, has a drainage area of 2.45 square miles. The
drainage area for Pucketa Creek above the confluence with The Unnamed Tributary is 10.23
square miles.
The peak discharge through the proposed opening based on the 2.45 square mile drainage area
will occur first and the peak for Pucketa will follow at a later time. The hydraulic investigation
for the proposed opening and the temporary crossing looked at the peak occurring on the
Tributary with Pucketa Creek at normal flow (See the write-up at the end of the Hydraulics
Section for further detail).
A FEMA Flood study was performed on the Unnamed Tributary. The discharges presented were
the 10, 50, 100 and 500-year storms. Se Item E Discharge Estimates under FEMA studies for a
listing of the discharges.
The Department is proposing a temporary runaround for the public’s use during construction.
The proposed runaround needs to be studied using the 2.33-year and the 100-year storms.
FEMA did not give a discharge for the 2.33-year storm. The Department, using the PSU-IV
method, found the 2.33-year storm to be 128 cfs (For the FEMA Discharge Data Table 5 and the
calculations for PSU-IV, see the attached sheets).
The roadway is listed as a Principal Arterial and a 50-year design storm with a discharge of 515
cfs will be used. The 100-year storm will flow at 590 cfs.
There are no major factors influencing the hydrology at this structure location including
tributaries entering The Unnamed Tributary to Pucketa Creek, reservoirs, dams, levees, or tidal
effects.