Tropical cyclones - Extreme Events: A Physical Reconstruction and Risk Assessment - page 84

Table 4.2 Modelled and surveyed heights of marine inundation during TC Chris

Approximate
distance from
crossing (km)

Latitude
(degrees
south)

Longitude
(degrees
east)

Modelled surge
and wave
set-up (m)

Surveyed
height of
debris (m)

Difference
in height
(m) Location

Survey site 1 10 19.92 120.178 3.88 5.4 1.52

Survey site 2 20 19.9 120.236 3.18 4.1 0.92

Survey site 3 27.5 19.89 120.273 3.38 4.2 0.82

Predicted site
of maximum
surge

30 19.87 120.30 3.98 N/A N/A

these plans, regulations or procedures. But wave run-up needs to be considered
because the extent of erosion, and hence potential undermining of human built
structures, will occur to the limit or elevation of that wave run-up, which can
be considerably higher than the storm tide (see Figure 4.9).
Tropical cyclones also have a major impact upon the natural environment.
Tropical forests, mangrove forests and coral reefs can all experience substantial
mortality during a cyclone event; the extent of the damage often being depen-
dent, but not always, on the intensity of the cyclone. The damage incurred by
coral communities from category 5 cyclones can be devastating though it is
unlikely that all corals are destroyed. Several studies have shown that there
is substantial spatial variation in damage following cyclones (Connell, 1978;
Connell et al ., 1997;Hughes and Connell, 1999)anddifferent intensity storms can
have varied effects. However, even when severe intensity cyclones do not cause
extensive damage to coral communities they most probably weaken the sub-
strate allowing severe damage to occur during subsequent less intense cyclones
(Lirman and Fong, 1997). Hence, the frequency of the most intense cyclones
is critical to the level of damage experienced by these communities over the
longer term. The same is true for tropical rainforests especially where both the
topography and canopy cover is uneven. Apart from human interference, it is
unlikely that other disturbance mechanisms, although nonetheless extensive
and significant (crown-of-thorns starfish, coral bleaching, phytophthora; Hughes,
1989;Hughes and Connell, 1999)wouldhavethesamelevel ofimpact as these
extreme intensity cyclones. Given that these events occur at frequencies higher
than the life span of many trees in the rainforest and corals on reefs (Nott and
Hayne, 2001), it is reasonable to assume that the present character of these com-
munities is a reflection of this disturbance regime. Tropical cyclones, therefore,
may be instrumental in shaping the character of these natural communities
and assist in promoting species diversity. Determining whether this is the case,