3. Results
3.1. Global impacts of SLR on wave height and wave induced velocities
Fig. 2a and Fig. 2b illustrate a typical model prediction for the variation of wave height (Hs) and wave induced velocity (Urms) across the reef-lagoon transect. The conditions shown are for the base bathymetry, average wind and wave conditions and both smooth and rough reefs. Wave height and velocity decrease across the reef flat due to wave breaking and friction, with wave heights subsequently increasing across the lagoon due to the wind. Velocities off the reef and in the deep lagoon are generally small compared to reef flat velocities. The sensitivity of the reef flat wave height (Hs) and wave orbital motion on the top reef (Urms) to reef bathymetry and surface roughness is illustrated in Fig. 3 and Fig. 4. The conditions correspond to the average off-reef wind-wave climate (i.e. Hs = 0.5 m, Tp = 4s and wind speed = 10 m/s). Results shown are for conditions at centre of the reef flat (midway between the reef rim and lagoon) unless stated otherwise. Clearly, wave height and orbital velocity decrease as the reef becomes wider ( Fig. 3 and Fig. 4), i.e., as the wave propagation distance over the reef increases. These patterns are altered under SLR but in a non-linear manner and change depending on the bathymetry. Not surprisingly, shallower reef flats act to reduce the average height of waves ( Fig. 3) and this effect is weakened under SLR, which increases effective depth, such that wave heights increase under SLR on all bathymetries and in all zones across the reef profile.