Theoretical Background - Response of Flood Events to Land Use and Climate Change - page 19

Any DEM should therefore be created with care, using the best available data
sources and processing techniques. Efficient detection of spurious features in
DEMs can lead to improvements in DEM generation techniques, as well as
detection of errors in the source data, as indicated above.
Since most applications of DEMs depend on representations of surface shape
and drainage structure, absolute measures of elevation error do not provide a
complete assessment of DEM quality [ 20 , 21 ]. A number of graphical techniques
for assessing data quality have been developed. These are nonclassical measures of
data quality that offer means of confirmatory data analysis without the use of an
accurate reference DEM [ 23 ].
2.4 Flood hazard: Concepts and definitions
World meteorological organization (WMO) [ 22 ] reported that floods events are
among the most common, costly and deadly of natural hazards and have been a
major concern to people residing near rivers and coastal areas throughout history.
Despite the great developments in science and technology in recent decades, the
hazards of flooding have not been eradicated [ 24 ].
According to the European Parliament and the Council of the European Union's
directives, the ''floods'' means the temporary covering by water of land not nor-
mally covered by water. This shall include floods from rivers, mountains torrents,
Mediterranean ephemeral water course, and floods from the sea in the coastal areas
and may exclude floods from sewerage systems [ 25 ].
UN-ISDR [ 26 ] also defined flood hazard as the ''potentially damaging physical
events, phenomenon or human activity that may cause the loss of life or injury,
property damage, social and economic disruption or environmental degradation''.
Wassef and Aysan [ 27 ] discussed the geographical distribution of disasters and
compared the flood hazard to other natural phenomenon in their research and
found floods as the worst phenomenon that affected people's lives. According to
Davis [ 28 ] investigation, there were 118 major flood events from the biblical
deluge to the present, and Wasseff [ 29 ] also listed 87 floods during the period of
1947-1991 which resulted in homelessness of at least 50,000 people. In 1887, one
of the worst recorded flood event occurred along the Yellow River in China. This
flood resulted in at least 1.5 million deaths and caused as many as 10 million
homeless ([ 28 ]. During 1982-1991, flood events left approximately 21,000 deaths
per year and affected 73 million persons per year [ 27 ]. The investigation results of
Wijkman and Timberlake [ 30 ] and Wasseff [ 26 ] indicate that since 1960, each
passing decade shows an increase in the number of flood disasters, and the number
of people which were affected by these flood events. Yen and Yen [ 31 ] has also
shown that relative flood damages in the USA as a fraction of the annual Gross
National Product, which expressed a declining trend between 1929 and 1993.
More recently, flooding has occurred in Pakistan in 2010, which has directly