Journal of Ecological Engineering Volume 16, Issue 2, Apr. 2015, pages 13–18 DOI: 10.12911/22998993/1854 Research Article FLOOD RISK FACTORS IN SUBURBAN AREA IN THE CONTEXT OF CLIMATE CHANGE ADAPTATION POLICIES – CASE STUDY OF WROCLAW, POLAND Szymon Szewrański1, Jan Kazak1, Marta Szkaradkiewicz1, Józef Sasik1 1 Department of Spatial Economy, Wroclaw University of Environmental and Life Sciences, Grunwaldzka 53, 50-357 Wrocław, Poland, e-mail: [email protected]; [email protected]; marta.szkaradkie- [email protected] Received: 2014.11.21 ABSTRACT Accepted: 2015.02.04 The uncontrolled sprawl of urban development exerts environmental impact in rural Published: 2015.04.01 areas. The aim of this study is to identify areas vulnerable to climate change in the context of implementation of policies adapting to climate change at the local level. Such areas can be defined as those where the negative implication of flesh flood over- lapping with soil sealing is observed. The study areas composed of municipalities which are influenced by the urban sprawl process of the city of Wroclaw, Poland. The analyses were performed using publicly available spatial data from aerial orthophoto- maps from 2004–2012, the satellite images; archival and current land use maps. The database CORINE 1990, 2000, 2006; Urban Atlas and geodatabase of the European Environment Agency were also of an important usage for this study. Keywords: climate change adaptation, water management, flood risk, soil sealing. INTRODUCTION Flood events are expected to increase in the fu- ture [Falloon and Betts 2010]. Integrated manage- The main climatic factors of floods, among ment of water resources requires the development other, include precipitation (volume of rainfall, its strategy of both mitigation and adaptation to up- intensity and duration) or air temperature (espe- coming changes in the environment. The choice of cially important for the formation of winter floods) the mitigation and adaptation solution depends on [Kundzewicz 2014]. Whereas the non-climatic the availability of economic resources and social factors include catchment topography, slopes, soil acceptance [Kundzewicz and Matczak 2012]. type, land use, density of the river network, etc. [De Roo et al. 2003, 2001]. Analysis of these con- ditions is necessary in order to correctly identify MATERIALS AND METHODS areas vulnerable to climate change, which in the case of Polish include mainly floods and droughts. The research area consists of the city of Wro- Historical records and ongoing hydro-meteo- claw and rural municipalities near Wroclaw: rological observations prove that there have been Kostomłoty, Miękinia, Oborniki Slaskie, Wisznia approx. 90 recorded floods in Oder river basin (an Mała, Czernica, Długołęka, Katy Wroclaw, Kobi- average of 1 over 10 years). Most of them were erzyce, Siechnice and Żórawina. Within these ad- small floods. Big floods occurred less frequently ministrative bodies, 266 cadastral units were care- [Dubicki et al. 2005]. Floods were not signifi- fully investigated. The analyses were performed cantly limited by hydro-technical treatments (riv- using publicly available spatial data from aerial er training, levees, flood-control reservoirs etc.). orthophotomaps from 2004–2012, the satellite The size of economic and social losses was often images; archival and current land use maps. The the result of improper land management in the database CORINE 1990, 2000, 2006; Urban At- catchment area. las and geodatabase of the European Environment 13 Journal of Ecological Engineering vol. 16(2), 2015 Agency were also of an important usage for this The greatest risk of flooding occurs in the study. Having the above sources analysed, changes Odra valley, particularly in the area of the city of in land use in the suburban area of Wrocław from Wroclaw, due to large amount of water (cadas- 1990 to 2006 were identified. The analyses were tral unit: Wroclaw, Paniowice, Kotowice, Bliza- performed using open GIS systems. The area cov- nowice–Trestno) and numerous tributaries of the ered by the study is subject to strong structural river. The smallest number of areas being at risk and spatial transformations. Spreading residen- of flooding are located in the valley of the river tial zone, increasing the number of investments Ślęza (cadastral units: Wroclaw, Żerniki Great Ga- in infrastructure and new industrial facilities have lowice), a bit more in the valley of the Bystrzyca caused changes in the quality of the natural envi- (cadastral units: Wroclaw, Samotwór, Skalka, ronment [Szewranski et al. 2013]. Romnów, Sadowice, Krobielowice, Gniechowice, The holistic analysis of the precipitation, mi- Zachowice, Kamionna and Czereńczyce) and the croclimate and hydrological conditions can be largest in the catchment of the Olawa (cadastral useful in choosing the location of investments units: Wroclaw, Mokry Dwór, Groblice, Zębice, in the context of adaptation to climate change. Grodziszów, Siechnice–Prawocin, Święta Katar- These conditions were compared with the current zyna) and the Widawa (cadastral units: Szymanów, trends in the spatial development of real estates. Psary, Krzyżanowice, Wilczyce, Wroclaw). The conclusions of these studies enable answer- This can be explained by downslopes of ing the question whether the current planning sys- each sub-catchment and soil permeability. If the tem requires more intense inclusion of an envi- downslopes are larger and soils are more com- ronmental impact assessment of the policy. Such pact peak flow occurs faster. That was a cause analyses seem to be necessary in the context of which triggered the fact that such a wave usually the implementation of The National Strategy for occurs much earlier in the area of Wroclaw, than Adaptation to Climate Change 2020 [SAP2020]. in the Oder River. There were two main reasons for the catastrophic floods in the Odra River in July 1997: an intense flow of water and impeded RESULTS drainage of water. The average annual precipitation in the study In order to identify the cadastral units where area is about 550–660 mm. A flood type that pre- the risk of flooding is greatest, hydrological maps vails in the Oder River is widespread rainfall based on floods’ greatest spatial distribution in the floods caused by prolonged rains of large scale case study area have been investigated (Figure 1). and considerable intensity. A flood type in the Figure 1. Flood plains in the case study area 14 Journal of Ecological Engineering vol. 16(2), 2015 tributaries of the Oder River (river: Bystrica, Ol- society and economy, severe heat waves must be awa, Ślęza, Widawa, etc.) is of torrential rainfall mentioned (continuous days with daily maximum caused among many factors by convective storms temperature ≥30 °C persisting for at least 3 days) in river basins. When analysing the effect of pre- and hot days (the temperature ≥30 °C), the most cipitation on flood creation one should take into common in the region of south-western part of the consideration not only annual, monthly or ten-day Poland. sums but also their distribution in time and space. In comparison to suburban are, solar ra- In the study area there are rarely embolic type of diation in Wroclaw is weakened, the number of flooding caused by local rising due to ice floes. hours of sunshine reduced, night cooling is less It is assumed that by 2030, the biggest threat to intense. The result is an increase of air temper- the economy and society will be extreme weather ature, known as the urban heat island, which is and climate (torrential rains, flooding, landslides, easily recognised during clear nights in summer heat waves, droughts, hurricanes, etc.). These phe- when there is more than 5 °C. The average annual nomena will occur with increasing frequency and relative humidity in the city centre is approx. 6% intensity, and will cover more and more areas of lower than outside the city during clear nights in the country. In the case study area heavy precipita- the summer by up to 40%. tion will increase in the first half of the summer, The geological structure and terrain affect the with intensities exceeding 5 mm/min, with a prob- development of the river network, and indirectly ability of ≥10%. The change in precipitation pat- the development of hydrographical networks and terns meaning a rapid increase in the number of the formation of river floods. Areas which have a days with high intensity precipitation (daily pre- large river network density are characterized by cipitation ≥50 mm for 2 days/decade (SAP2020, high rainfall, low evaporation losses, varied ter- 2013) will occur on the majority of the land in rain and impermeable surface. Poland (including the study area). From the hydrological point of view, the most Climatic conditions of Wroclaw exhibits important geological and soil factor that has got characteristics typical of large urban and indus- impact on the formation of the outflow is the per- trial agglomerations, where the impact of the meability of the ground. This feature determines economic activity is reflected by a change in the the seepage of rainwater and depends on the physical characteristics of the surface, air pollu- constant physical properties of the soil. The phe- tion and artificial heat emission produced in mu- nomenon which is very important is the growth nicipal and industrial processes. Whereas non- of built-up areas, especially in urban areas. This urbanized areas are characterized by significant is done at the expense of green spaces, reducing deviations of particular climate components - in the area of land covered with natural cover. Wro- particular precipitation and temperature. The in- claw in hydrological terms resembles a mountain creased rainfalls in Wroclaw were identified for basin, where because of the intensive real-estate the city centre, the Old Town and Karłowice development, increased runoff occurs (Figure 2). and less intensive rainfall in the eastern districts Cadastral units with the highest soil sealing (Biskupin, Swojec), as well as western – the aver- (above 5%) are Wilkszyn, Jeszkowice, Sośnica- age annual total precipitation is about 30–50 mm Różaniec, Ratowice, Żórawina, Łany, Pietrzyko- larger [Schmuck 1967].