Theoretical Background - Response of Flood Events to Land Use and Climate Change - page 29

2.8 Land Use Change and Anthropogenic Factors
Apart from climatic factors that have affected floods (as mentioned in Sect. 2.6 ),
according to Kundzewicz and Schellnhuber [ 96 ] another significant reason, for
increasing flood hazards can be related to nonclimatic anthropogenic factors:
Changes in socioeconomic systems include land-use changes such as deforesta-
tion, urbanization, elimination of floodplains area, as well as river regularizations
[ 96 ], which lead to reducing of water storage, reducing of infiltration capacity, and
increasing of runoff coefficient [ 97 ]. WMO [ 22 ] also reported that the first category
of nonclimatic anthropogenic factors effects resulting from human actions which
have affect on the ecosystem changes are deforestation and urbanization. These
lead to changes in the ecosystem that magnify the consequences of heavy pre-
cipitation, converting this precipitation into floods of a greater severity than
otherwise would have resulted [ 22 ].
Xiaoming believes that land use change is a major reflection of the land eco-
system change, which will then lead to the hydrology regime changes. The
hydrology regime changes can then feedback on environmental and land use
change, which generates a complex and international system.
By floodplain development, increasing accumulation of population and wealth
in flood-prone areas, humans have been driven to occupy unsafe areas (e.g.,
informal settlements on floodplains), thereby increasing the loss potential.
Where urbanization occurs on the floodplain, the ability of the floodplain to
attenuate a flood peak by promoting storage, infiltration, and alternative flow
pathways is reduced. This effect is greatly enhanced where flood defenses are
erected; such structural measures may also cause residents to lose their sense of
natural river dynamics and reduce the perceived risk for further development [ 98 ].
The history analysis of urban growth indicates that urban areas are the most
dynamic places on the earth's surface. Despite their regional economic impor-
tance, urban growth has also a considerable impact on the surrounding ecosystem
changes [ 99 ]. In the last few decades, an increase in urban areas has occurred in
the world, and demographic growth is one of the major factors responsible for
these increasing changes. By 1900 only 14 % of the world's population was
residing in urban areas, but it had increased to 47 % by 2000 [ 100 ]. Urban growth
is a common phenomenon in almost all countries over the world. Currently,
increases in urban areas are the major environmental concerns that have to be
analyzed and monitored for any future planning.
Urbanization and its increasing trend may have particularly severe influences
on small catchments, where a high percentage of the catchment area may undergo
a change in land use within a short time period. In a larger catchment, the effects of
land use change would to a greater extent be damped by the remainder of the
catchment area [ 101 - 103 ]. Since the end of the 1960s, the scientific literature
reported the results of studies on the possible effects on the fluvial regime of
intense deforestation and urbanization which had occurred in some drainage basins
of the United States [ 104 ]. Some previous studies also have analyzed the effects of