of the Verde Island Passage, Philippines - weADAPT

chapter 1 • vulnerability assessment of marine ecosystems and fisheries to climate change: exposure
80 knots. Even during this high intensity event, winds
within the Verde Passage move across the passage
thus fetch is limited and waves do not become fully
developed. The maximum significant wave heights
were about 10m and were found in the area east and
northeast of Marinduque.
For the first period, the center of the storm can be
seen in the area west of Marinduque with relatively low
significant wave heights (Figure 22a). Within the Verde
Passage, waves can still be significant (8m) although
smaller in magnitude compared to the waves in the
Sibuyan Sea. An estimate of the amount of wave energy
available at the coast to stir up sediments and infer
erosion potential is the plot of bottom orbital velocity
(Figure 22b). Note that the largest values of orbital
velocity are found in areas with shallow gently sloping
bathymetry such as along the coast of Tayabas Bay and
the northern coast of Lubang.
For the second period used was after a period of 6
hours, the typhoon has moved westwards and the
center can be found west of Puerto Galera. Maximum
significant wave heights can still be found in the
northwestern Sibuyan Sea along the coast of Batangas
and Quezon (Figure 23a). Wave heights within the
VIP although quite large, are still much lower than the
maximum significant wave heights.
Surprisingly the areas with high bottom orbital velocities
are essentially the same as the model results 6 hours
earlier (Figure 23b). These areas have two things in
common; shallow gently sloping bathymetries and wide
expanse of water facing the coast.
With almost 160 typhoons going through within 200 km
from Verde Island since 1952, it becomes necessary
to integrate the effects of all these typhoons to assess
the vulnerability with regards to storminess. This was
a) b)
20'
9
20'
0.9
14ºN
8
14ºN
0.8
7
0.7
40'
6
40'
0.6
latitude
20'
5
4
latitude
20'
0.5
0.4
13ºN
3
13ºN
0.3
2
0.2
40'
1
40'
0.1
120ºE 30' 121ºE 30' 122ºE 30'
longitude
120ºE 30' 121ºE 30' 122ºE 30'
longitude
Figure 22. Simulations for a category 5 typhoon when storm was still on the eastern side of the VIP. a) Significant wave height
during typhoon with center west of Marinduque, and b) Bottom orbital velocity during typhoon with center west of Marinduque.
a) b)
20'
9
20'
0.9
14ºN
8
14ºN
0.8
7
0.7
40'
6
40'
0.6
latitude
20'
5
4
latitude
20'
0.5
0.4
13ºN
3
13ºN
0.3
2
0.2
40'
1
40'
0.1
120ºE 30' 121ºE 30' 122ºE 30'
longitude
120ºE 30' 121ºE 30' 122ºE 30'
longitude
Figure 23. Simulations for a category 5 typhoon when storm was still on the western side of the VIP. a) Significant wave
height (m) during a typhoon with the center located near Puerto Galera, and b) Bottom orbital velocity (ms -1 ) from wave model
forced by typhoon with center west of Puerto Galera.
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