Book 1 - City of St. Petersburg

BASIS OF DESIGN BOOK 1
3 GENERAL PLANNING CRITERIA
SITE AND URBAN
DESIGN CRITERIA
(continued)
Water Levels
Tides in the Tampa Bay region are mixed semi-diurnal tides,
meaning water levels may exhibit one high and low tide (diurnal)
or two high and two low tides (semi-diurnal) in any given day or
cycle.
Figure 3.26 describes the relationship between the three
different water level datum systems relevant to the new Pier
(NAVD 88, NGVD 29 and the St. Petersburg Datum) and lists key
water level data for the St. Petersburg Pier. Tidal information
was obtained from NOAA Station 8726520 located near the St.
Petersburg Coast Guard station. This data was accumulated over
19 years of measurements, from 1983 to 2001.
Sea Level Rise
With sea levels around the world rising, human populations living
in coastal regions and ecosystems in the natural environment
may potentially be impacted. Global average sea level rose at
an average of around 1.7 +/- 0.3 mm per year from 1950 to 2009
and at a satellite-measured average rate of about 3.3 +/- 0.4
mm per year from 1993 to 2009, an increase on earlier estimates.
Though it is unclear whether the rate reflects an increase in
the underlying long term trend, observed sea level rise has
been taken into consideration in the design of the new Pier, in
particular because the project has a 75-year life span.
In response to wave action and sea level rise, the bottom of the
lowest structural members are designed to be 1 ft higher than
the base flood elevation. This will place the top surfaces of the
new Overwater Drive and Bridge at a level 12 ft above mean sea
level and more than 3 ft above the deck of the existing Pier.
Floodplain Management
Preliminary code analysis and floodplain management
considerations are as follows.
Scour at the structure foundation varies depending on the
structure type and dimensions. The depth and design impact of
scour on the proposed structure should be evaluated for a 100-
year return period event.
Storm surge data from the most recent FEMA Flood Insurance
Study (FIS) for Pinellas County (2003) lists the water level at 5.7
ft for a return period of 25 years, 7.0 ft for a return period of 50
years and 8.3 ft for a return period of 100 years.
Figure 3.27 is used to administer the National Flood Insurance
Program for Pinellas County, Florida. An explanation of the
design implications for the new Pier, which is subject to extreme
environmental conditions, can be found in the ‘Accessibility and
Code Requirements’ section of this Report.
For additional information pertaining to floodplain management
refer to Appendix K: Flood Resistant Design and Construction,
which contains highlights of ASCE 24-05, a referenced standard
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THE NEW ST. PETERSBURG PIER