Basis of Design Book 2 - City of St. Petersburg

4.0 MODEL INPUTS
4.1 SIMULATION PERIODS FOR FLUSHING ANALYSES
Based upon the ERP Basis of Review Document, the maximum allowable time to achieve 90
percent flushing of docking facilities is 4 days. As such, the hydrodynamic runs for the flushing
evaluation are relatively short. The key to fully evaluating the flushing conditions is to assure
that reasonably conservative estimates of the primary forcing mechanisms (tides and winds) are
utilized. Analyses of the tide and wind data identified a 30-day period where the full range of
tidal conditions (diurnal and semi-diurnal) were represented, as well as periods of relatively low
wind energy. Higher winds will drive more overall circulation and exchange and will not
represent a sufficiently conservative condition.
Analyses of the available wind and tide data identified October 2010 as having the full range of
tidal conditions along with relatively low wind energy, as well as concurrent and continuous data
availability at other stations in the bay. October 2010 was chosen for the model calibration
period.
Analysis of tidal energy data from 2006 through 2011 was performed by calculating the total
water surface elevation movement for a moving window of averaged successive four day (24hr)
periods throughout the 5 year span, and then ranking the values from largest to smallest. That
ranking was then evaluated to determine on which dates tidal energy was at or below the lower
10 th percentile of occurrence for the data set. For the target month of October 2010, the period
of October 14 th thru the 21 st was found to have tidal energy at or below the established 10 th
percentile rank, and was chosen for running flushing simulations. A total of five, four day
duration analysis runs were made with 100 percent dye concentration being used in the marina
basin at the onset of day one, and mixing modeled for a 4- day period. This range five different
sets of four days was used to be certain that all likely combinations of tidal phasing were
analyzed.
The flushing simulation periods were:
• Flushing Run 1 : October 14 – 17 , 2010 < 3.7 th Percentile 4-Day Average Tidal Energy
• Flushing Run 2 : October 15 - 18 , 2010 < 0.7 th Percentile 4-Day Average Tidal Energy
• Flushing Run 3 : October 16 - 19 , 2010 < 0.5 th Percentile 4-Day Average Tidal Energy
• Flushing Run 4 : October 17 - 20 , 2010 < 3.3 th Percentile 4-Day Average Tidal Energy
• Flushing Run 5 : October 18 – 21 , 2010 < 7.4 th Percentile 4-Day Average Tidal Energy
GNV/2012/122381A/8/8/2012
4-1