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CLIMATE CHANGE
TROPICAL CYCLONES
TROPICAL CYCLONES
Global Warming
Damage Components
Sea Level Rise
Storm Surge
WIND
EXACERBATED IMPACTS
Higher sea level = deeper faster flowing storm surge +
higher breaking waves + faster floating debris, resulting
in higher hydrodynamic pressure, stronger wave impact
and higher wave run-up, stronger debris impact.
Continually growing potential for damage to the built
environment in coastal regions, from impact of storm
surge driven by recurring hurricanes.
 1988 Ricardo A. Alvarez
 Positive
Wind-velocity pressure
 Negative
Wind-velocity pressure
 Vortices
 Eddies
 Wind stagnation
 Flying debris impact
Water impact  Wind impact x 1.9x10 by volume a
a (Assumes: Surge flow = 8.3 m/s, Wind velocity = 53.3 m/s)
QUANTIFYING THE IMPACT OF STORM SURGE
The design methodology is based on calculating the impact energy of the
medium (water or air) to quantify the pressure per unit of area acting on
the building. This is based on the well known equation for energy:
or energy = mass x square of velocity
In the case of storm surge a two-step process is involved in calculating the
actual load applied to the building by the rushing water:
1. Calculate the hydrodynamic pressure using the following equation:
𝑷=
𝟏
𝟐
Cd
 V2
2. Calculate the total hydrodynamic load :
Where:
P=
Cd=
 =
V =
F =
A=
 2005 Ricardo A. Alvarez
PROBLEM
To establish design criteria for a building in coastal locations engineers must
quantify the loads acting on it under the impact of wind and water, during a
hurricane.
𝒆=
 Hydrodynamic pressure
 Wave impact
 Hydrostatic pressure
 Drag
 Scouring
 Erosion
 Wave runup
 Floating debris impact
Water  800 x density of air @ sea level. In the case of
storm surge this ratio could reach 1000:1 because of
salt water and sediment content.
 2005 Ricardo A. Alvarez
𝟐
𝒎𝒗
WATER
hydrodynamic pressure
drag coefficient
mass-density of water
velocity of flow
total force against building
submerged area of bldg. face
F = PA
In the case of wave loads the process is similar, but with the additional step of
calculating the height of the wave breaking against the building
Velocity of flow is a critical factor in the calculation of
loads acting on a building as a result of storm surge and
waves.
Relative to this, standards, such as ASCE7, and codes
used by engineers, such as the Florida Building Code or
the International Building Code are rather general about
this specific topic or do not address it at all. SLOSH, the
model used by NOAA to simulate storm surge, does not
include velocity of flow or waves.
NOAA’s Hurricane Research Division suggests using the
speed at which a hurricane is moving as a proxy for
velocity of flow for storm surge, but this could result in
large uncertainties.
We lack a reliable source of velocity of flow data to use
in calculating forces generated by the most damaging
component of a hurricane, one which is being
exacerbated by climate change!
RECOMMENDATION:
The scientific community in collaboration with relevant
federal agencies would make an invaluable contribution
by pursuing research, which would allow engineers to
have reliable data on the velocity of storm surge flow on
a basin-specific basis. This could be incorporated on a
storm-surge flow-velocity map similar to the basic wind
speed map in ASCE-7, to be adopted by building codes.
1 2011 RICARDO A. ALVAREZ
2 Florida Center for Environmental Studies (CES), Florida Atlantic University (FAU)
[email protected]; www.mitigat.com; (305)931-0871; FAX (305) 931-4704