Geoscience Reference
In-Depth Information
are developing a system whereby electricity can be
transferred between towers using microwaves, thus
eliminating cables.
STORM SURGES
(Wiegel, 1964; Coastal Engineering Research Center, 1977;
Anthes, 1982)
Intro
duction
Storm surge, as alluded to above, plays a significant
role in tropical and extra-tropical cyclone damage.
Storm surge was the main cause of death in
Bangladesh (East Pakistan) in the 1970 and 1985
cyclones; the main cause of destruction in the
February 1953 North Sea storm; and the main reason
that waves were so effective in eroding beaches in
the May-June 1974 storms in New South Wales. In the
United States storm surge is considered the main
threat necessitating evacuation of residents from
coastal areas preceding tropical cyclone landfall. Here,
evacuation was instituted in response to the Galveston
hurricane disaster of September 1900, during which
6000 people died because of storm-surge inundation.
The phenomenon is also a recurring hazard in the
embayments along much of the Japanese and south-
east Chinese coastlines. For example, approximately
50 000 people lost their lives around Shantou
(Swatow), China, on 3 August 1922 and, as recently as
September 1959, 5500 people lost their lives in Ise
Bay, Japan, because of storm surges. In this concluding
section, the causes of storm surge and the concept of
probability of occurrence will be discussed.
Fig. 3.24
The effect of freezing precipitation and wet snow on wires
and tree branches in Ontario, Canada (photograph from
Canadian Atmospheric Environment Service).
period of between 35 and 85 years, and that the
damage was comparable to a storm that struck
the same region in December 1929. In Canada, the
storm paralyzed the city of Montreal and its population
of four million for several weeks. Here, the accumula-
tion of ice around objects was unprecedented and
amounted to 100 mm at some locations - double any
previous storm. Around Montreal, more than 1000
power transmission towers and 30 000 wooden utility
poles crumbled under the weight. Over 120 000 km of
power lines and telephone cables were downed. Close
to 1.4 million people in Quebec and 230 000 in Ontario
were without electricity for over a week. Temperatures
dropped to -40°C afterwards and 100 000 people had
to be evacuated to shelters for a month because of a
lack of home heating. Twenty-five people died - mainly
from hypothermia, 20 per cent of Canada's work force
missed work, 25 per cent of its dairy industry was
suspended and five million sugar maples lost the
capacity to produce syrup for 30 to 40 years. Over
16 000 Armed Forces personnel had to be brought in
to assist overwhelmed utility workers. The total coast
to the economy was in excess of $CAD2 billion.
Two recent innovations may go a long way towards
minimizing the downing of power lines by ice. The first
utilizes a property of ice whereby the top layer of water
molecules exposed to air is quasi-liquid and conducts
electricity. Ice can be melted from power lines simply
by passing a high-frequency electrical current at
50 watts m
-1
along the cables. The second innovation
completely does away with power lines. The French
Cau
ses
Storm surge is generated by a number of factors
including:
• wind set-up,
• decreases in the atmospheric weight on a column of
water,
• the direction and speed of movement of the
pressure system,
• the shallowness of the continental shelf, bay or lake,
and
• the shape of the coastline.
This discussion will ignore any addition effects due to
river runoff, direct rainfall, wave set-up inside the surf
zone, or Coriolis force.
The main reason for storm surge would appear to be
the piling up of water by wind. The exact amount of
