FLORIDA GEOLOGICAL SURVEY
Panhandle Gulf Coast (Balsillie and others, combined storm tide (super-elevated water 1987a, 1987b, and 1987c, respectively), level including contributions of wind stress, and D is the survey date. Please note that barometricpressure decrease, dynamic wave the value of c changes with time and setup and astronomical tides) corresponding location; the current value of c for a to a 50-year return period elevation is particular coast is a representative regression normally used for design calculations. value. Superimposed upon the storm tide still water level is a design wave height, normally a
MONERGIS77TIC TIDAL DATUM breaking wave height corresponding to Hb 10
PLANE APPLICA TIONS or Hbl. As previously noted, where a wave shore-breaks is dependent on the water
Thus far, the above application/use depth which, in turn, is dependent on patexamples have been described as syner- terns of sediment redistribution occurring gistic. That is, horizontal shoreline shift and during event impact. Sediment redistribution volumetric change results are referenced to is largely a function of offshore sediment a datum so that they can be compared transport and longshore bar formation spatially within a North American or global (Balsillie, 1982a, 1982b, 1983a, 1983b, context. The scientific need to do so has 1983c, 1984a, 1984b, 1984c, 1985a, been robustly demonstrated. Even more, 1985b, 1985c, 1985d, 1985e, 1986; considerable analytical work is required to Balsillie and Carter, 1984a, 1984b, etc.). An determine such synergistic results which example is illustrated in Figure 9. cannot be simply recalculated to another
datum. Such design work calculations are site-specific because results will be
As described in the introduction there influenced by the pre-impact site-specific are, however, other quite different concep- profile configuration. There is no intention, tual applications of astronomical tidal datum nor at this time a need to compare such planes. Some of these are not necessarily results to other localities. Should such an bound by the need for a spatial tidal datum application need arise (e.g., a generalized convention. These are described as modeling effort or an accounting need to monergistic applications. The purpose, here, assure consistency in design application(s)), is to demonstrate several such examples. then the reference base should be MSL.
However, such transformations to other
DESIGN SOFFIT ELEVATION datums can be easily accomplished, CALCULATIONS compared to much more involved recalculation of synergistic data (i.e., volumes
"Soffit elevation" is a generic term or horizontal distances). meaning the elevation to the underside of the
lowest supporting structural member exclud- EROSION DEPTHISCOUR CALCULATIONS ing the piling foundation, say, for a pier or
single- or muti-family dwelling. Such Site-specific design work such as elevations are calculated for extreme minimum pile embedment requires elevations associated with the impact of knowledge of the design surface elevation. extreme events (i.e., storms and hurricanes). This elevation necessarily includes erosion The goal is to raise the structure to an depth (e.g., longshore bar trough elevation or elevation so that it is above the destructive beach erosion elevation), additional scour hydraulic force elements which will pass caused by the pile, and sediment below the soffit and through the piling liquefaction. In essence these design foundation. For a pier, for instance, a peak elevation calculations are treated in the same manner as design soffit elevation
48