LIST OF FIGURES 



1 . 1 Breakwater failure modes 2 



2. 1 Flume plan (top) and profile (bottom) views for incipient motion 



experiment 13 



2.2 Definition sketch for typical structure profile 14 



2.3 Velocity time series for one wave period with H,= \2 cm, T= 1 s, J, = 24 cm 

 and d^ = 8.8 cm measured 1 cm outside the armor layer 19 



2.4 Velocity vector for one wave period for armor lifting measured 1 cm outside 



the armor layer with H, = 8.4 cm, f= 2s,d, = 24 cm, and ^^ = 17 cm 20 



2.5 Vertical velocity time series outside (top) and inside (bottom) armor layer 

 with H, = 12 cm, T= 1 s,d, = 24 cm, and di = 8.8 cm for the outer 

 measurement and di = 13 cm for the inner measurement 20 



2.6 Measurement locations for vertical velocities shown in Figure 2.5 21 



2.7 Maximum vertical velocity versus the square root of wave steepness for wave 

 periods T= 1 and 2 s and relative depths rd = 0.36, 0.5, and 0.7 22 



2.8 Vertical variation of vertical velocity under a steep wave fi-ont across the 



armor layer as a function of wave steepness 27 



2.9 Photographs of sphere motion during a typical incipient motion experiment 

 forPlan4 30 



2.10 Incipient motion criterion (Equation 2.14 with v^ = 61.8 cm/s) versus wave 

 steepness 31 



3 . 1 Sketch of breakwater profile with definition of eroded area and depth of 



cover 34 



