All cities are considered to be vulnerable systems due to ongoing climate changes [1
]. Depending on the macroclimate position, as well as land cover structure of the urbanized landscape, quite obvious consequence of climate change has been the occurrence of urban heat islands (UHI) and surface urban heat islands (SUHI) [3
]. Depending on the urban forms of built-up areas and the characteristics of green infrastructure at the level of micro-scale, UHI has a negative impact on the thermal comfort of citizens [5
]. Climate change, however, causes an extreme level of hydrologic regime in an urban landscape [6
]. On one hand, municipalities have to solve problems related to droughts, lack of groundwater and a limited amount of natural moisture for urban greenery [8
]. On the other hand, they have to introduce measures to mitigate the impacts of heavy rains, floods on a built-up area of a city, capacity overload of drainage systems that cause negative impact on quality of water in watercourses [2
]. The abovementioned issues became relevant for the cities in Central Europe as well [4
The planning for adaptation of cities to climate changes must interlink a traditional approach of urban and strategic planning with modern scientific knowledge of urban climatology and urban hydrology, which contribute to the design of effective measures for specific types of sites in the city [7
]. Methodological procedures are being developed that integrate adaptation measures into complex environmental tools for practice [14
]. An important part of the interconnection of hydrological and climatological models is the balance of energy flows [15
]. The concept of blue-green infrastructure (BGI) is often recommended as a suitable tool for city adaptation [16
]. Using BGI is presented as a new system for stormwater management, which supports the quality and the retention of water in the urban landscape. Moreover, it is beneficial for public space, for adaptation to climate change, as well as for biodiversity [18
]. Unlike traditional approaches that are focused on technical solution to drain stormwater through combined sewerage as quick as possible out of the urban areas, BGI is designed as a system similar to natural water circulation. It connects green infrastructure as an organized system of urban greenery and stormwater management in the city [17
]. It can always be problematic, when two approaches—a technical one and a nature-based one—are differentiated in a simplifying way [19
]. Thus, there are blended terminologies occurring in the literature, such as blue-green-gray [20
], hybrid or mixed infrastructure [21
The urban planning of sustainable cities requires specialized maps that visualize spatial differentiation of the urban landscape according to appropriate environmental parameters [14
]. Based on the definition of local climate zones (LCZ), tools for modeling of urban climate have been developed that can be used for the purpose of planning for adaptation measures [22
]. Professional discussion on the LCZ delimitation has been happening in terms of scale of spatial units processed via GIS-based [25
], selection of thermal analysis techniques [28
] or automatic data processing [27
]. The current analysis of European LCZ studies shows the need to focus on the refining LCZ and higher accuracy in defining training areas [28
Different properties of LCZ affect thermal comfort mainly through evaporation depending on air flow and the effect of green infrastructure [30
]. Thermal comfort conditions have a significant daily regime [32
]. What is good about LCZ when the urban climate is modeled, is that they can be also used for making scenarios on how the development of the urbanized landscape impact climatic conditions or for assessment of proposed adaptation measure’s impact. LCZ application is usually focused on urban climate modelling, on UHI intensity delimitation, on thermal comfort assessment [28
] eventually on energy balance of buildings, especially in terms of building carbon emission [33
]. Standardized LCZ units can also be used as a basis for assessing the impact of urban landscape transformation on ecosystem services [34
]. An important factor, which influences UHI intensity, is how the BGI elements are spatially distributed in the city [11
]. Thus, it is expected that there are certain causalities across LCZ classes and spatial characteristics of BGI in cities. Discovering these causalities would enable the application of a world-wide standardized process of LCZ definition to broader scale of climate change impacts in cities. This intention is consistent with a trend to strengthen multidisciplinary approaches of adaptation measures that should not only help to decrease thermal discomfort of citizens [11
] but also contribute to the solution of extreme hydrological events [19
], to support biodiversity in cities [36
] and enhance the quality of public space [37
]. Holistic approaches become the basis for integrated planning methodology for sustainable development of cities [38
This study is focused on the links between LCZ and ecohydrological qualities in our paper. Only a few studies dealing with interactive models between energy and water in urban areas have been focused on the linkages between LCZ and hydrologic processes [15
]. A dominant link of this interaction is a process of evapotranspiration [40
]. Our research is focused especially on a relationship between LCZ and the runoff regime of areas in a context with BGI elements.
The analysis of geodata is based on a case study of the city of Pilsen (Czech Republic), for which previous projects defined and demarcated LCZ [43
], as well as ecohydrological spatial units with a link to BGI proposals. Both zonations in the city come up from different geodata and their spatial units have different scales. This fact reflects in a methodology of the analysis. That is why the authors first present the methodology of ecohydrological zonation in an urban landscape, which was made in GIS as a basis for blue-green infrastructure planning in Czech cities.
The goal of the analysis is to compare the ecohydrological zonation of the territory of the city with the standardized climatological zonation based on LCZ. A fundamental question of our study is whether defining of LCZ can help to plan measures not only to mitigate thermal stress, plus also provide more complexed adaptation measures that take into account other climate changes impacts, especially extreme hydrological events.
In the methodological part of the paper, the ecohydrological zoning of the urban landscape, which was created in GIS as a basis for planning the blue-green infrastructure of cities in the Czech Republic, is presented. The essence of the methodology is a two-level categorization of territorial units, which is based on the possibility to determine some ecohydrological parameters at various levels of detail. The resulting ecohydrological zoning of the city of Pilsen and parameterization at the level of microstructures was compared with the zoning of the city by a standardized procedure for defining LCZ. The resulting evaluation of raster cells of individual LCZ classes according to ecohydrological parameters must be considered as a case study, the generalization of which is limited. The limit of generalization is both the specific characteristics of the urban landscape of Pilsen and also own procedure of ecohydrological zoning, based on available data sets for the city. The comparison of methodological procedures for the definition of LCZ and zoning of ecohydrological microstructures with parameterization based on elementary areas results in a different level of scale for distinguishing the characteristics of the urban landscape. Standardized procedures for delimiting LCZ are aimed at defining larger territorial units of the same morphology of built-up areas and land cover in a grid scale of 100 × 100 m. A more universal use of the LCZ classification would be helped by the choice of more detailed data and the resulting scale of spatial units [25
], or a link to territorial units of administrative-functional use [29
]. For practical application of the results is more suitable, when units delimited as urban blocks according to type of built-up area are used for the assessment of the territory on the basis of LCZ [27
]. On the other hand, the standardization of procedures is limited by the fact that LCZ categorization is applied worldwide in different climatic zones with different urban development.
Defining and parameterizing the ecohydrological properties of microstructures purposefully takes into account the functional use of areas and the slope of the area, seeking to distinguish elementary areas up to a grid level of 0.5 m. However, the process of defining microstructures has not been fully automated and the accuracy of the resolution depends on the underlying data, such as the availability and quality of the urban green spaces inventory. Based on the zoning of the area into ecohydrological microstructures, adaptation measures can be better spatially targeted, for example thanks to a separate assessment of street corridors. Despite the mentioned differences in climatological and ecohydrological zoning, it was proved on the example of the territory of the city of Pilsen that both zonations correspond to a certain extent. In other words, the defined LCZ classes show different ecohydrological properties.
However, the presented statistical description of both zonings of the area cannot prove a detailed dependence of climatic and ecohydrological properties for two reasons: it is not based on direct measurements and cannot take into account detailed differences within units. For example, the categorization of buildings does not take into account the occurrence of green roofs and facades, which may affect the outflow or evapotranspiration [35
]. However, this must be demonstrated by detailed research and measurements on individual surfaces in different microclimatic position [10
The zoning of the area according to LCZ is, of course, too rough to capture the microclimatic differences affected by the detailed parameterization of street corridors, buildings and individual surfaces of the city in the horizontal and vertical scale. The used ecohydrological classification is also unable to distinguish some details of the area, e.g., greenery leaf size (leaf area index), green roofs hydration degree [35
], but it showed the possibilities of supplementing the structure of data on individual areas of LCZ, so that they are more generally applicable for the evaluation of the potential of BGI of the city.
The determined distribution of the level of runoff, evapotranspiration and BAF coefficients in the territory of Pilsen mainly corresponds to the share of permeable and impervious areas, which is one of the standardized parameters defining the types of LCZ. The permeability parameters of the areas mediate a significant link to other properties of the area—the potential distribution of infiltration, runoff and evaporation of rainwater. Results confirm that types of residential areas are significantly associated with some types of ecosystem service [63
The links between water circulation and climatic parameters are demonstrated on the basis of modeling the energy significance of the evapotranspiration process [40
]. However, less attention is paid to runoff links, although this is a more measurable component of the hydrological balance. The inclination of the area as an important parameter of runoff is distinguished. Climatological zonations take it into account only in the case of the effect on exposure to solar radiation.
There is currently a discussion about the possible extension of the LCZ classification to aspects of forms of urban landscape relief, which are described as part of non-urban effects. The proposed combination of LCZ types and orographic classification of urban sites is driven by an effort to better capture the topoclimatic conditions in the hilly relief in some cities. The use of the classification of relief forms could thus support a holistic expression of the characteristics of the urban landscape [64
], also taking into account runoff conditions. However, a more accurate distinction of the slope of the area is more important for determining the runoff conditions.
As our analysis of the inclination of the area according to the types of LCZ on the example of Pilsen has shown, there are differences between the individual types (Table 6
, Figure 6
). There is also a large variance of values for LCZ 6, 8 and 9. However, these differences do not explain the level of distribution of the runoff coefficient in individual LCZ. LCZ with higher values of inclination (LCZ 9, LCZ 6) represent the area of detached houses, which can be situated with their gardens on the slopes of river valleys, etc. However, this character of the urban landscape with the representation of greenery generally shows lower values of runoff than flat areas built up by large buildings of industrial, trade and services (LCZ 8) or modernist high-rise apartment buildings (LCZ 5). The assumption that the area of LCZ 8 needs to be addressed as a priority not only from the point of view of thermal overheating [65
], but also from the point of view of ecohydrology, was confirmed. These areas also show unfavorably high values of surface runoff. Moreover, in the case of Pilsen, LCZ 8 has a significant representation in some sectors of the inner city, where industrial zones extend [45
]. To discuss the effect of inclination, it should be added that this parameter has no additional effect on the parameterization of runoff for impervious surfaces, because the standards assign a level of coefficient 1 regardless of the inclination of the area.
Impermeability of areas and lack of greenery in the built-up area, typically in the microstructures of production and storage areas, classified mainly in LCZ 8, are essential for the risk of extreme runoff events. In this case, it is confirmed that the delimitation of LCZ in cities can be used to plan not only the mitigation of thermal stress, but also to more comprehensive planning of adaptation measures. However, it is appropriate to supplement the zoning of LCZ at a more detailed level with other parameters of the area important for BGI planning (e.g., slope of the area, possibilities of water retention in the area or risk of pollution of direct runoff).
Other links between LCZ typology and ecohydrological zoning exist through parameters such as e.g., surface covered by high vegetation, surface covered by low vegetation [61
]. In the territory of Pilsen, differences in the level of ecosystem services of individual city zones classified according to LCZ were proved via BAF indicator. In the detail of individual plots or functional microstructures, it is possible to develop the use of complex BGI indexes, such as biotope area factor. However, complex indicators should not only take into account rainwater management, but also other ecosystem services, including the level of microclimatic effects of the area.
In this case, it is possible to explain the variability of the values of ecohydrological parameters of individual types of LCZ by the required accuracy of the resolution of both zonations and the accuracy of the used data on the territory. However, more general conclusions can be made after testing in a larger number of cities, because the results may be affected by the specific structure of the territory and the development of built-up areas in the city of Pilsen. More detailed research and verification of links in other cities [34
] can thus be a way to generalize the parameterization of LCZ to the level of expression of other ecosystem services, such as water retention, impact on health, air quality, etc. The result could be a comprehensive zoning system of the city as a basis for environmental modeling, including not only climatic aspects, but also runoff conditions, the possibility of solar energy production or effects on air quality [14
The presented study brings new findings in three fields: (1) it compares methodological approaches to ecohydrological and climatological zoning of the cities, (2) it records the ecohydrological properties of the areas of individual LCZ classes in the model area, (3) it discusses the possibilities of supplementing the classification parameters of LCZ with other aspects, especially the slope of the territory.
(1) A comparison of two approaches to the zoning of the territory of the city of Pilsen has shown that it is possible to seek a connection between methodological approaches based on research in both climatology and ecohydrology. Based on the presented case study, it is possible to recommend further verification of the links between climatic and ecohydrological processes in the city, both towards the generalization of knowledge for Central European cities and towards standardization of data sources and their effective processing for city management.
(2) The direct connection of climatological and ecohydrological properties of the area is enabled by common parameters such as permeability of areas or the degree of greenery. A significant difference factor between the properties defining LCZ and the parameters of ecohydrological microstructures is the slope of the area, influencing the degree of surface runoff. In the territory of Pilsen, however, it turned out that the slope of the territory is not an explanatory factor of differences in the runoff coefficient in the built-up areas between LCZ classes.
(3) The results indirectly show that the slope of the area is related to the spatial distribution of LCZ types. This could be developed when defining orographic subtypes of LCZ for use at least in Central European conditions. This direction of supplementing the LCZ classification with non-urban effects will help a holistic approach to the classification of the urban landscape.
Further unification of approaches for the processing of analytical maps will be beneficial for the practice of cities in the field of adaptive measures to climate change, because it is also appropriate to unify tools of adaptation and look for the synergistic effects of BGI planning.