Human activities are diverse and a key component in influencing the level of hazard1
and risk2
presented by the physical environment. The relationship between human activities, flood
hazards and risks is an area of particular interest given the arguments surrounding climate
change, and the increasing productivity of human populations and stresses on the physical
environment that such developments initiate. In fact, the alteration of the physical environment,
be it through natural processes or through human activities will always have some sort of impact,
whether negative or otherwise. The impact of natural hazards is no longer considered a function
of geological processes or climatic factors alone. There are numerous examples of human
activities and modification of the natural and physical environment that have increased the risks
of natural hazards. For instance in Italy, the impact of landslides is greater in the residential
areas on hill tops than in less populated areas of the Italian landscape (Guzzetti et al., 2005). The
increased risks of damage from earthquakes and volcanoes, loss of life and livelihood in
Indonesia is higher than ever before because of the density of population and increase in the built
environment (Boer and Sanders, 2002; Thornton, 1996). In small island states, predominantly in
the Pacific, tropical cyclones alone have the potential to dent an entire economy particularly
where natural resources are the mainstay of the economy (McKenzie et al., 2005)3
. In places like
New Orleans, its structural measures such as the levees designed for a 100 year return period
flood in magnitude, failed in the face of Hurricane Katrina, a category 3 hurricane. The failure
of the structural measures has been attributed to the engineering of the levees and the sociopolitical
influences at the time of their construction which failed to address its weaknesses and
implement measures beyond the 40 year life span of the levees (van Heerden, 2007).