100
Table 5.25: The Results of the Mass Transport and Return Flow Calculations for Trial 8.
Mass Transport Location Return Flow Location Y Depth
(Ft/Sec) (Ft) (Fte/Sec) (Ft) (Ft)
(Calculated) (Calculated)
50.43 688 -19.60 640 13.96
13.07 592 -12.83 544 10.55
3.87 496 -4.56 448 2.52
-11.26 5.20
2.13 416 4.96 368 1.63
1.41 3.73
0.78 336 3.44 288 1.36
From the tables, it is apparent that the mass transport values and the return values at each location do not equal each other. The overwash event is the direct cause of this inequality. In a non-overwash case, it is necessary that the total mean volume flux be zero. In other words, the shoreward mass flux should be negated by the seaward return flow (Equation 5.3).
f udz Q = 0 (5.3)
When overwash occurs, a percentage of the total volume of water travels over the island. The portion that flows over the island is now equal to the sum of the mass transport minus the return flow, or, there is a net positive volume flux at any section (Equation 5.4).
f udz= Q (5.4)
Since there is a lack of detailed velocity data at any one location, there is not enough evidence to assure that the return flow calculated is an exact representation of the true velocity field. Thus, the sum of the mass transport minus the return flow does not equal that net volume flux (ie. Q) found over the island for these experiments. However, the data from each trial does gives credence to equation 5.4 in general.