experts said that it was the storm surge that left tacloban, the whole province of leyte and other areas with utter destruction. CP david, my geology professor back when i was a UP diliman freshie, explains what this super alien phenomenon all about.
Storm Surge 101: What they are, and how to prepare for them
"Daluyong." This is the closest Filipino translation to what we now know as a "storm surge," according to National Artist and Chairman of the Komisyon ng Wikang Filipino Virgilio S. Almario.
The majority of Filipinos are probably unfamiliar with the Filipino
term, but by now everyone knows how destructive storm surges can be in
the aftermath of super typhoon Yolanda. Storm surges, like other natural
hazards present in the country—e.g., earthquakes, volcanic eruptions,
floods and landslides—will surely happen again in the future. Thus, it
is only appropriate that we learn about what storm surges really are:
when the ocean reclaims part of the land during a typhoon.
What's a storm surge?
A storm surge is an abnormal rise of the ocean generated by a weather
disturbance such as a tropical cyclone, over and above the predicted
high tide mark. The US National Weather Service says that the rise in
water is mainly wind-driven and therefore, the stronger the winds
brought by a typhoon, the higher the storm surge.
Hurricane Katrina, which hit the southern coast of the United States in
2005, had maximum sustained winds of 280 kph and produced 8-meter storm
surges. Katrina was one of the strongest typhoons to hit land—but it's a
far cry from Yolanda’s 315 kph winds, according to the Joint Typhoon
Warning Center.
Along with sustained wind
speeds, another critical factor is the size of the typhoon itself. The
bigger the typhoon, the longer it will have an impact on a particular
area as it moves along. Size will have a direct correlation with how
long the storm surges will be in effect.
'Coastal geometry'
Resio and Westerink (2008) discussed other factors that contribute to
the height of storm surges. They say that besides the typhoon’s wind
speed and size, the geometry of the coastal area may very well tell how
far storm surges will go inland.
A coastal area
with a very gentle slope—you know this from beaches where you can walk a
hundred meters and the water will still only be up to your waist—is
more prone to storm surges.
In contrast, beaches with steep ocean floors will be less prone to surges.
Resio and Westerink also said that, as waters come in towards the land,
friction between the advancing water and the ocean floor underneath can
slow down a storm surge. Coral reefs and rocky shores help dissipate
the wave energy.
Surge barriers
Barriers—man-made seawalls and breakwaters and natural mangroves and
wetlands—also help block storm surges up to a certain extent.
Typhoon Pedring in 2011 caused storm surges to flood the Roxas
Boulevard baywalk and Hotel Sofitel by up to 4 feet. The surges would
have been higher, if not for the Manila Bay breakwaters and seawall.
Another factor that worsened the effect of the storm surge in Tacloban
is the city’s location: Yolanda may havepushed the ocean water from San
Pablo Bay, into its narrowest part San Juanico Strait, where Tacloban is
located.
There might still be debate on whether
daluyong is the best Filipino word for storm surge but there will
definitely be no argument on the threat it poses and the need for us to
do something before it happens again. — TJD/HS, GMA News
Dr.
Carlos Primo "CP" David is a geology professor at the University of the
Philippines-National Institute of Geological Sciences (NIGS). He earned
his Ph.D. in Environmental Science and Geology from Stanford University
and is the project leader of Climate X.
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