Tidal prism

Figure 7.12 Radium-derived groundwater fluxes from Pettaquamscutt estuary (USA), calculated using a simple box model aquifer recharge, based on a tidal prism (TP) model and residence time (8 and 20 d) of the estuary. (Modified from Kelly and Moran, 2002.)...

Tidal prism volume of water that flows in and out of an area between higher high tide and lower low tide. 

The tide advances up the Connecticut and the Housatonic Rivers as a progressive wave (Le Lacheur and Sammons, 1932). Tides and circulation in the Thames River are described by Tolderlund (1975). The East River is a tidal straight with most of its tidal prism derived from New York Harbor (Bowman, 1976a). 

BIS and the Atlantic Ocean. When the alongshore component of the wind reverses direction, the excess water level begins to fall and, as the intensity of the west wind increases, the surface slope both inside and outside the two Sounds reverses. An outward net flow of water from LIS is then indicated by the current meters. The mean tidal prism of LIS is 5.47 X 10 m The greatest excess volume of water in the Sound during the 15-16 December storm is 3.4 x 10 m or 62% of the mean tidal prism. The potential energy of the excess water at maximum bh is 18 x 10 MJ the potential energy at the top of the tidal oscillation of mean range is... 

P tidal prism A area V volume subscripts C, E, and F channel, ebb shoal, and flood shoal, respectively C empiric or derived coefficient j,m,n,p,q empiric or derived power W width of inlet throat M gross longshore transport in a year. 

Tidal prism can also be calculated as the product of the effective bay surface area served by the subject inlet and the tidal range. It can also be obtained from a computation of water discharge, as through a numeric model. By definition of a discharge, the mean-maximum velocity Vmm is ... 

Tidal prism-inlet channel area relations... 

The observations of LeConte are remarkable in that not only did he deduce a direct (linear) relation between channel cross-sectional area and tidal prism, but also that the empiric coefficient is larger if less sediment is driven by waves to the inlet entrance. Unprotected harbors are exposed to wave action and longshore transport of sediment, whereas inner harbor entrances would be protected or sheltered to some degree from wave action. Therefore, for the same value of tidal prism, protected inlets can have larger channel cross-sectional area. 

Jarrett comprehensively analyzed the relation between spring or diurnal tidal prism and inlet channel cross-sectional area. He compiled 162 data points for 108 inlets, with 59 inlets located on the Atlantic coast, 25 on the Pacific coast, and 24 on the Gulf coast of the USA. Jarrett s objective was to determine if tidal inlets on all three coasts of the USA follow the same tidal prism-inlet area relationship, and to investigate the change in that relationship for stabihzed and non-stabilized (natural) inlets. The results are summarized in Table 31.3, referring to the equation ... 

Table 31.3. Inlet-area and spring or diurnal tidal prism regression values found by Jarrett for Ac = CP (area units of m, prism units of m ) tidal inlets on US coasts.

Fig. 31.9. Data on inlet channel area and spring tidal prisms (after Ref. 39).

Trend lines from the data of Jarrett and of Hume and Herdendorf are plotted in Fig. 31.10. For the same value of tidal prism, channel cross-sectional areas for New Zealand entrances in sheltered areas (bays, protected inlets) tend to plot higher than those for unprotected or unsheltered entrances. Entrances on the (unsheltered) northeast coast of New Zealand plot on top of the all-inlet trend line for US inlets. 

Tidal prism versus ebb shoal volume relationships... 

Others have confirmed the essential finding of Walton and Adams that the volume of the ebb-tidal shoal is related to the tidal prism. Marino and Mehta examined 18 inlets on the east coast of Florida. They found that tidal prism was a leading parameter controlling ebb-shoal volume, with the ratio of inlet width to depth being a secondary factor. Hicks and Hume conducted a similar analysis for 17 inlets in New Zealand and confirmed the overall results of Walton and Adams. Hicks and Hume also considered the angle between the ebb jet and the shoreline in their correlations. 

Pig. 31.11. Volume of ebb-tidal shoal as function of tidal prism, all coasts (after Ref. 40). 

Tidal prism versus flood-shoal volume... 

Quantitative relations were obtained between flood shoal area and spring tidal prism, for which it is noted that correlation coefficients were low B values in the range of 0.21-0.39) for widely scattered data that exhibited a broad trend. The... 

Buonaiuto and Kraus S analyzed the bathymetry of 18 inlets around the coast of the USA to determine a predictive expression for the minimum depth over crest her of the ebb shoal. It was reasoned that, because both incident waves and the tidal prism are expected to be controlling independent variables for ebb shoal development, a parameter combining both average annual significant wave height Hs and... 

Fig. 31.12. Minimum depth over crest of an ebb shoal and product of average annual significant wave height and tidal prism as (HsPy -...

J. T. Jarrett, Tidal prism-inlet area relationships, GlTl Report 3, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS (1976). 

T. Shigemura, Tidal prism-throat width relationships of the bays of Japan, Shore Beach 49(3), 34-39 (1981). 

R. J. Byrne, R. A. Gammisch and G. R. Thomas, Tidal prism-inlet area relations for small tidal inlets, Proc. 17th Coast. Eng. Conf, ASGE (1980), pp. 2517-2533. 

Tidal prism will increase — greater scour of all foundations Seawalls and other engineered structures... 

Tidal prism will increase — potentially greater scour and removal of sediment... 

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