Initial 1 hr
Meas 18 hrs
Calc 18 hrs
Distance Alongshore (m)
Fig. 5. Result of model validation for Case 4.
Sensitivity Analyses. Encouraged by the above results, it was decided that
the physical model layout could serve as a basis in a sensitivity analysis for
examining numerical model performance. Three groups of analysis tests were
conducted through variation of wave height, wave direction, and model boundary
As seen from Fig 4, tombolos never developed in the physical model. In
GENESIS, while keeping other values unchanged, the wave height was gradually
increased to produce tombolos. For wave heights twice as large as in the physical
model, tombolos were developed in GENESIS as illustrated in Fig. 6 on the up-
drift side of the two T-head groins in the left side of the model (A and B). Up-
drift of the right-most groin (C) there was not enough sand to form a tombolo. In
addition, a simulation was performed with wave heights half of the original. As
seen in the figure, the reduced wave height gave only modest shoreline change.
For varying incident wave direction, the model performed consistently. In
addition to the original wave direction of 14 deg, simulations were made for
directions of -28 and +14 deg. One simulation was also made for wave angles
varying sinusoidally between -14 and +14 deg, completing one full variation
period over one hour. As seen in Fig. 7, tombolos did not form, irrespective of
the wave angle.