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A. Magnuszewski
in generating floods. To analyze the flood occurrence and spatial distribution, we
assume that the processes of flood generation are statistically stationary and are not
a subject of trend. In the study of [1] it has been proved that Elbe and Odra rivers do
not show any increase of flood frequency in long time horizon. Based on long-term
time series they found decreasing winter flood occurrence, while summer floods
showed no trends [2] so the process of flood generation can be considered as random
and not showing any trend. Also, in the study of [3] based on the data from period
1951–2006, it has been found no evidence of a trend in frequency and magnitude of
floods.
New study results of potential effects of a global warming on meteorological and
hydrological extremes at regional scales are given at [4]. In their work an ensemble
of EURO-CORDEX RCP8.5 scenarios is used in connection with distributed hydrological model to assess the projected changes in flood hazard in Europe through the
current century. A positive trend for the maximum daily precipitation is found in
most of the study region, with scale and statistical significance becoming stronger
moving toward Eastern and Northern Europe. Hydrological response to increase of
precipitation is more complicated due to a interaction of different runoff formation
processes, reduced snow cover accumulation, increase of evapotranspiration. In the
study it was found reduction of peak discharges in southern Spain, Scandinavia and
Baltic countries, while a large portion of central Europe and the British Isles are likely
to experience a progressive increase in the magnitude and frequency of maximum
discharges.
According to report of European Environmental Agency [5] there is observed an
increase of flood losses in Europe since the 1970s. In Poland recent catastrophic
floods of 1997 on the Odra River and 2010 on the Vistula River had more negative
consequences much more losses than previous events that they led to significant
changes in flood risk estimation methods. The trend for increasing losses from river
floods is primarily attributable to increase of society wealth, but also growing exposure to risk due to improper spatial planning and growth of settlement at flood prone
areas. In Poland after the flood of 2010 there has been initiated a national program
of flood reduction risk called ISOK (informatics system of risk assistance and evaluation). As the first step of the program it was made inventory of the major historical
floods and their range. In this program a whole country has been covered by the
accurate measurements of elevation DEM (Digital Elevation Model). This data are
indispensable for calculations of flood range of given probability with the use of
hydrodynamic models. In ISOK terrain elevation has been measured by the lidar
altimeter in the basic field element of 1 × 1 m, with the density 4 points/m
2 at the
open areas (including forest), and in the cities 12 points/m
2 . Accuracy of elevation
measurement is on a flat country surfaces in the range of ≤0.15 m, and for the cities
≤0.10 m. In the forest area accuracy is lower – 0.25–0.30 m.
Accurate DEM and hydrodynamic modeling have been applied to prepare for the
major river valleys maps of flood range and flood risk. The ISOK flood risk maps can
be obtained in pdf. format from https://mapy.isok.gov.pl/imap/. Example of ISOK
map index is shown at Fig. 14.1.
A. Magnuszewski
in generating floods. To analyze the flood occurrence and spatial distribution, we
assume that the processes of flood generation are statistically stationary and are not
a subject of trend. In the study of [1] it has been proved that Elbe and Odra rivers do
not show any increase of flood frequency in long time horizon. Based on long-term
time series they found decreasing winter flood occurrence, while summer floods
showed no trends [2] so the process of flood generation can be considered as random
and not showing any trend. Also, in the study of [3] based on the data from period
1951–2006, it has been found no evidence of a trend in frequency and magnitude of
floods.
New study results of potential effects of a global warming on meteorological and
hydrological extremes at regional scales are given at [4]. In their work an ensemble
of EURO-CORDEX RCP8.5 scenarios is used in connection with distributed hydrological model to assess the projected changes in flood hazard in Europe through the
current century. A positive trend for the maximum daily precipitation is found in
most of the study region, with scale and statistical significance becoming stronger
moving toward Eastern and Northern Europe. Hydrological response to increase of
precipitation is more complicated due to a interaction of different runoff formation
processes, reduced snow cover accumulation, increase of evapotranspiration. In the
study it was found reduction of peak discharges in southern Spain, Scandinavia and
Baltic countries, while a large portion of central Europe and the British Isles are likely
to experience a progressive increase in the magnitude and frequency of maximum
discharges.
According to report of European Environmental Agency [5] there is observed an
increase of flood losses in Europe since the 1970s. In Poland recent catastrophic
floods of 1997 on the Odra River and 2010 on the Vistula River had more negative
consequences much more losses than previous events that they led to significant
changes in flood risk estimation methods. The trend for increasing losses from river
floods is primarily attributable to increase of society wealth, but also growing exposure to risk due to improper spatial planning and growth of settlement at flood prone
areas. In Poland after the flood of 2010 there has been initiated a national program
of flood reduction risk called ISOK (informatics system of risk assistance and evaluation). As the first step of the program it was made inventory of the major historical
floods and their range. In this program a whole country has been covered by the
accurate measurements of elevation DEM (Digital Elevation Model). This data are
indispensable for calculations of flood range of given probability with the use of
hydrodynamic models. In ISOK terrain elevation has been measured by the lidar
altimeter in the basic field element of 1 × 1 m, with the density 4 points/m
2 at the
open areas (including forest), and in the cities 12 points/m
2 . Accuracy of elevation
measurement is on a flat country surfaces in the range of ≤0.15 m, and for the cities
≤0.10 m. In the forest area accuracy is lower – 0.25–0.30 m.
Accurate DEM and hydrodynamic modeling have been applied to prepare for the
major river valleys maps of flood range and flood risk. The ISOK flood risk maps can
be obtained in pdf. format from https://mapy.isok.gov.pl/imap/. Example of ISOK
map index is shown at Fig. 14.1.