1. CAPE 2009 P2/U1 #6
a) From the passage above, identify FOUR characteristics of a tsunami which
contribute to its destructive power. [4 marks]
Four characteristics of a tsunami which contribute to its destructive power are:
Recession of the water leads to huge waves in excess of 20 feet in some cases.
The velocity of the tsunami as it makes touchdown, is so powerful, it destroys everything
in its path.
The loud hissing sound of the tsunami is associated with its impact on land as it may be
so powerful it modified the beach completely.
The height of the water as it swept inland may have been destructive as it covered the 10
foot top of the beach ridge.
b) Describe the operation of the Pacific Tsunami Warning System. [ 6 marks]
The Tsunami Warning System in the Pacific has the functions of monitoring seismological
and tidal stations throughout the Pacific Basin to evaluate potentially tsunami genic earthquakes
and disseminating tsunami warning information. The Pacific Tsunami Warning Center (PTWC)
is the operational center of the Pacific Tsunami Warning System.
If the location and magnitude of an earthquake meet the known criteria for generation of a
tsunami, a tsunami warning is issued to warn off an imminent tsunami hazard. The warning
includes predicted tsunami arrival times at selected coastal communities within the geographic
area defined by the maximum distance the tsunami could travel in a few hours. A tsunami watch
with additional predicted tsunami arrival times is issued for a geographic area defined by the
distance the tsunami could travel in a later time period.
Tsunami watch, warning and information bulletins are disseminated to appropriate
emergency officials and the general public by a variety of communication methods. The PTWC
disseminates bulletins to local, states, international and national users as well as the medis. These
users, in turn, disseminate the tsunami information to the public, generally over commercial
radio and television channels.

2. CAPE 2009 P2/U1 #6
c) Explain how climate, the characteristics of the river basin, and human activities
might cause rivers to flood. [20 marks]
Rivers can flood as a result of climate, characteristics of the river basin and human
activities. These all have different root causes for which the river floods.
Firstly, a river might flood because of the climate. Climate is defined as the atmospheric
conditions of a geographical area over a long period of time usually 30-35 years. In the some
Caribbean countries such as Trinidad and Tobago which have a distinct dry season and wet
season, can cause rivers to flood on its own. During the dry season, the precipitation levels are
considerably lower than that of the wet season. By extension, the dry season is usually
characterized by temperatures exceeding on average, 32oC. Such temperatures cause severe
drought in these Caribbean islands. Severe temperatures are usually accompanied by forest fires
which in many cases remove all the tree cover in mountainous regions. When this vegetation
cover is removed by forest fires, it means that it has the potential for flooding in the future. This
is because; extremes in temperatures restrict infiltration and increase surface runoff. When the
wet season arrives, and precipitation levels are once again high, increased rainfall usually causes
increased surface runoff to exceed the infiltration capacity. This results in an increase in the
levels of water in rivers hence causing rivers to flood its banks. A case in point, the 2010 dry
season in Trinidad and Tobago led to severe flooding in the wet season.
Secondly, the characteristics of the river basin might cause rivers to flood. The river basin
is the area drained by the river. Characteristics of the river basin include; basin size and relief. If
a basin is small it is likely that rainfall will reach the main channel more rapidly than in a larger
basin where the water has much further to travel. This means that the river has the potential to
flood where the basin size is smaller as the length of time it takes for water to reach the main
river, may not give sufficient time for the water in the river to drain properly and it may back up
and cause flooding. Additionally, the slope of the basin and its valley sides also determines
whether a river floods. In steep sided upland valleys, water is likely to reach the river more
quickly than in gently sloping lowland areas. This, as a result, may cause a river to flood since;
again, the river may not get enough time to drain the water.
Lastly, human activities can also cause rivers to flood. Land management techniques such
as drainage systems, digging ditches, ploughing up and down a slope may also increase the risk
of flooding by a river. However, urbanization and deforestation are the two most common human
activities to increase the possibility of flooding by a river. By building new towns or increasing
the size of urban areas makes land surface impermeable. It increases the amount of runoff by
removing topsoil for construction and compacting the ground with earth moving machinery.
Also, straightening river channels and lining them with concrete to enable building plans to
proceed increases runoff. This leads to faster delivery of water downstream of the urban area

3. CAPE 2009 P2/U1 #6
increasing the risk of flooding in those areas. Deforestation is also another human cause that
causes a river to flood. The removal of trees reduces interception and evapotranspiration
resulting in increased runoff and soil erosion. The eroded material finds its way into water
courses where it aggrades the river bed. This reduces channel capacity increasing the likelihood
of flooding. Deforestation in the Himalayas, the upper reaches of the River Ganges, may be
increasing the frequency of flooding in Bangladesh.