17 Water Problems in Urban Areas
405
was significantly lower than at the same time in the neighboring suburban catchments
[35].
In cities located by large rivers, there is a possibility of winter floods: ice jam and
frazil ones. A significantly greater threat occurs in the lower reaches of the Vistula
River than the Odra River. On the Vistula during this type of flood, the absolute
historical maximum water levels were recorded [109]. After building the dam of the
water reservoir in Włocławek and putting it into use in 1970, the risk of flooding
associated with the river icing and the occurrence of congestion distinctly increased
above the reservoir, and decreased below it [110]. The largest disastrous ice-jam flood
in Poland occurred in January 1982 in the upper part of the Włocławek reservoir,
covering, among others, left-bank part of the city of Płock [111, 112]. In turn, a
huge frazil jam formed on Wisła cross-cut in Gda´ nsk ( ´
Swibno) in March 1956 and
caused a unique high water accumulation in the river and the breaking of the flood
embankment. On the regulated section of the Odra, congestions threatening Szczecin
are eliminated by icebreaking actions (e.g. in March 2018). Floods of this type also
occur on the Warta and Note´ c rivers (including Wiele´ n at the turn of 2011/2012).
Storm floods occur in cities located at river estuaries on the Baltic Coast, on
˙
Zuławy and the Vistula Lagoon and the Szczecin Lagoon [113, 114]. They are a
hydrological effect of the movement of low pressure from the Norwegian Sea to
the east or south-east, mainly in the period from November to February. There are
inflows of sea waters into riverbeds and river valleys, and water levels rise up to
2 m in them [115, 116]. An example of such an extreme event was a storm flood in
January 1983, which occurred in cities along the entire Baltic coast ( ´
Swinouj´ scie,
Kołobrzeg, Ustka, Władysławowo, Gda´ nsk), and was caused by a wind of 8–10
o on
the Beaufort scale [117]. The storm flood was also lately reported (October 2009)
in Elbl˛ ag on the Vistula Lagoon. A backwater in the Elbl˛ ag River bed was formed
then.
Massive material losses in cities over the last dozen or so years have been caused by
floods resulted from failures of water accumulation structures on rivers. The reasons
were extremely high sums of atmospheric precipitation in their catchments, and in
some cases design, implementation and exploitation errors of a dam and reservoir.
Examples of such events come from all over Poland. On the night of February 2,
2000, the reservoir dam on the Młynówka River (Warmian-Masurian Voivodeship)
was destroyed and a wave of a height of approx. 7 m flooded Górowo Iławeckie
[67]. Unfortunately, three fatalities were the result of this flood. Another incident
was a failure of the structural coffer of the Wióry reservoir on July 24, 2001, on the
´
Swi´ slina River in the Holy Cross Mountains. After an extremely high rainfall (daily
sum in Kielce—155.2 mm), with high humidity of the ground in the catchment, the
water accumulated and the embankment was destroyed. The surge wave exceeding
the height of 8 m caused significant damage in two cities far away from the event, i.e.
in Kunów and Ostrowiec ´
Swi˛ etokrzyski (8.5 km and 17.0 km away, respectively).
Another spectacular example of the collapse of an accumulating construction, the
effects of which were also felt in two cities (in Bogatynia and Zgorzelec), was the
destruction of the dam in Niedów on the Witka river (Dolno´ sl˛ askie Voivodeship) in
405
was significantly lower than at the same time in the neighboring suburban catchments
[35].
In cities located by large rivers, there is a possibility of winter floods: ice jam and
frazil ones. A significantly greater threat occurs in the lower reaches of the Vistula
River than the Odra River. On the Vistula during this type of flood, the absolute
historical maximum water levels were recorded [109]. After building the dam of the
water reservoir in Włocławek and putting it into use in 1970, the risk of flooding
associated with the river icing and the occurrence of congestion distinctly increased
above the reservoir, and decreased below it [110]. The largest disastrous ice-jam flood
in Poland occurred in January 1982 in the upper part of the Włocławek reservoir,
covering, among others, left-bank part of the city of Płock [111, 112]. In turn, a
huge frazil jam formed on Wisła cross-cut in Gda´ nsk ( ´
Swibno) in March 1956 and
caused a unique high water accumulation in the river and the breaking of the flood
embankment. On the regulated section of the Odra, congestions threatening Szczecin
are eliminated by icebreaking actions (e.g. in March 2018). Floods of this type also
occur on the Warta and Note´ c rivers (including Wiele´ n at the turn of 2011/2012).
Storm floods occur in cities located at river estuaries on the Baltic Coast, on
˙
Zuławy and the Vistula Lagoon and the Szczecin Lagoon [113, 114]. They are a
hydrological effect of the movement of low pressure from the Norwegian Sea to
the east or south-east, mainly in the period from November to February. There are
inflows of sea waters into riverbeds and river valleys, and water levels rise up to
2 m in them [115, 116]. An example of such an extreme event was a storm flood in
January 1983, which occurred in cities along the entire Baltic coast ( ´
Swinouj´ scie,
Kołobrzeg, Ustka, Władysławowo, Gda´ nsk), and was caused by a wind of 8–10
o on
the Beaufort scale [117]. The storm flood was also lately reported (October 2009)
in Elbl˛ ag on the Vistula Lagoon. A backwater in the Elbl˛ ag River bed was formed
then.
Massive material losses in cities over the last dozen or so years have been caused by
floods resulted from failures of water accumulation structures on rivers. The reasons
were extremely high sums of atmospheric precipitation in their catchments, and in
some cases design, implementation and exploitation errors of a dam and reservoir.
Examples of such events come from all over Poland. On the night of February 2,
2000, the reservoir dam on the Młynówka River (Warmian-Masurian Voivodeship)
was destroyed and a wave of a height of approx. 7 m flooded Górowo Iławeckie
[67]. Unfortunately, three fatalities were the result of this flood. Another incident
was a failure of the structural coffer of the Wióry reservoir on July 24, 2001, on the
´
Swi´ slina River in the Holy Cross Mountains. After an extremely high rainfall (daily
sum in Kielce—155.2 mm), with high humidity of the ground in the catchment, the
water accumulated and the embankment was destroyed. The surge wave exceeding
the height of 8 m caused significant damage in two cities far away from the event, i.e.
in Kunów and Ostrowiec ´
Swi˛ etokrzyski (8.5 km and 17.0 km away, respectively).
Another spectacular example of the collapse of an accumulating construction, the
effects of which were also felt in two cities (in Bogatynia and Zgorzelec), was the
destruction of the dam in Niedów on the Witka river (Dolno´ sl˛ askie Voivodeship) in