17 Water Problems in Urban Areas
401
of 6.9% of the entire country (21.6 thousand km
2 ). For comparison, in Europe,
the urban population is 74.2% of the total population [75]. The quoted data indicate an advanced state of urbanization and industrialization processes in Poland,
and this contributes significantly to changes in the water cycle and the degradation
of the aquatic environment and related ecosystems. Therefore, there are conflicts
between human activities, water protection as well as ensuring the safety of people
and property. Therefore, it is necessary to conduct sustainable development in these
areas, taking into account the multidirectional needs of water and socio-economic
environments [71, 76, 77].
The chapter presents selected issues of the water environment of Polish cities
regarding:
• periodic excess of rainwater and surface runoff,
• flood risk,
• the importance of small streams and reservoirs,
• water usage and wastewater treatment.
17.2 Periodic Excess of Water
The specificity of urban areas is their large sealing. It results mainly from the coverage
of a significant amount of area by residential buildings, commercial buildings, warehouse halls, industrial facilities, etc. The buildings are accompanied by impermeable
road surfaces or poorly permeable surfaces of sidewalks, squares and car parks. This
means that the sealed area with not-rough and impervious surfaces without vegetation
increases. There are then clear hydrological and geomorphological consequences in
small urban catchments. The former result mainly from the reduction of infiltration
and increase of the surface runoff component, and the second from significant spatial
differentiation and intensification of erosion processes, including surface wash, especially along artificially oriented zones, most often of a linear nature and accumulation.
The extensive drainage and hydrotechnical network enable quick drainage of excess
water along with the carried matter to a river or a collecting channel. Here, due to the
large and almost simultaneous supply of water and matter from different areas of a
catchment, there is a rapid increase in flows and fluvial transport. Rapid reaction of
a drainage system in an urbanized area is conducive to an increase in the energy of
flowing waters, which initiate and intensify the processes of erosion, transport and
accumulation in river channels [25–28, 30, 35, 78, 79].
The share of built-up and urbanized lands in the total area of Poland in 2016 was
5.37%, and it shows an upward trend [80]. This indicator in all Polish cities in 2014
reached 27.8%, and in individual cities, it showed a significant variation, especially
in small cities: from 1.5% in Krynica Morska (Pomorskie Voivodeship) to 87.7% in
Piastów (Mazowieckie Voivodeship). In capitals of voivodeships, the share of sealed
areas in 2016 ranged from 31.3% in Szczecin to 55.4% in Warsaw, with its average
value of 42.1% (Fig. 17.1).
401
of 6.9% of the entire country (21.6 thousand km
2 ). For comparison, in Europe,
the urban population is 74.2% of the total population [75]. The quoted data indicate an advanced state of urbanization and industrialization processes in Poland,
and this contributes significantly to changes in the water cycle and the degradation
of the aquatic environment and related ecosystems. Therefore, there are conflicts
between human activities, water protection as well as ensuring the safety of people
and property. Therefore, it is necessary to conduct sustainable development in these
areas, taking into account the multidirectional needs of water and socio-economic
environments [71, 76, 77].
The chapter presents selected issues of the water environment of Polish cities
regarding:
• periodic excess of rainwater and surface runoff,
• flood risk,
• the importance of small streams and reservoirs,
• water usage and wastewater treatment.
17.2 Periodic Excess of Water
The specificity of urban areas is their large sealing. It results mainly from the coverage
of a significant amount of area by residential buildings, commercial buildings, warehouse halls, industrial facilities, etc. The buildings are accompanied by impermeable
road surfaces or poorly permeable surfaces of sidewalks, squares and car parks. This
means that the sealed area with not-rough and impervious surfaces without vegetation
increases. There are then clear hydrological and geomorphological consequences in
small urban catchments. The former result mainly from the reduction of infiltration
and increase of the surface runoff component, and the second from significant spatial
differentiation and intensification of erosion processes, including surface wash, especially along artificially oriented zones, most often of a linear nature and accumulation.
The extensive drainage and hydrotechnical network enable quick drainage of excess
water along with the carried matter to a river or a collecting channel. Here, due to the
large and almost simultaneous supply of water and matter from different areas of a
catchment, there is a rapid increase in flows and fluvial transport. Rapid reaction of
a drainage system in an urbanized area is conducive to an increase in the energy of
flowing waters, which initiate and intensify the processes of erosion, transport and
accumulation in river channels [25–28, 30, 35, 78, 79].
The share of built-up and urbanized lands in the total area of Poland in 2016 was
5.37%, and it shows an upward trend [80]. This indicator in all Polish cities in 2014
reached 27.8%, and in individual cities, it showed a significant variation, especially
in small cities: from 1.5% in Krynica Morska (Pomorskie Voivodeship) to 87.7% in
Piastów (Mazowieckie Voivodeship). In capitals of voivodeships, the share of sealed
areas in 2016 ranged from 31.3% in Szczecin to 55.4% in Warsaw, with its average
value of 42.1% (Fig. 17.1).