Jana Podhrázská

Aerodynamic Parameters of Windbreak Based on its Optical Porosity

Abstract The paper summarizes the results of wind velocity measurement in different distances from windbreak in combination with optical porosity (OP) determination in different periods. Experimental data were obtained by direct measurement of wind speed and OP analyses of images of four windbreaks in Southern Moravia (part of Czech Republic). Wind speed at 2 m above the soil surface in a defined distance from windbreak had been measured since 2006. Thirty images of different phenological stages of selected windbreaks from 2006 to 2010 were analyzed. Windward or leeward images were converted into black and white spectrum. All available measurements were used for a map creation. The highest values of OP (up to 50%) are achieved in non-vegetation period. Due to the high OP variability in height of terminal tree branches “OP reduced” was also assessed (just squares to 2/3 height of windbreaks were evaluated). The wind speed reduction on the leeward side relatively strongly correlated with OP value. The highest correlation was found out when the wind speed measurement at 50 m on leeward side was used. The dependence decreases with increasing distance. Full foliage in summer (10% OP) reduces a wind speed about 60% at 50 m and about 30% at 150 m on the leeward. These values for non-foliaged windbreaks decrease to 80 and 90%. Maximum distance of windbreak effect on wind speed reduction was found out by the extrapolation of the curves constructed using the regression equation of wind speed reduction in dependence on OP and different distances from the windbreak. Regardless of OP value, the reduction effect disappears at a distance of 250 m. The quietest zone of evaluated windbreak with an average height of windbreaks 15-18 m was detected in the area about four times the height (4H). The effect of windbreaks decreases with increasing porosity.

Landscape Metrics as a Tool for Evaluation Landscape Structure – Case Study Hustopeče

Abstract The contribution presents the method of evaluation of rural landscape development in Hustopeče microregion by means of the analysis of landscape structure. Based on the computation of the values of landscape ecological indexes, development and typical and specific features in selected time horizons are interpreted. The time of the stable cadastre mapping (1825) was chosen as the initial period, other periods were the actual situation at present (2006) and the time between these two periods (the sixties of the 20th century). It is an agricultural landscape in southern Moravia used for intensive farming. Analysis results illustrate long-term continuing landscape utilization for agricultural production. All evaluative indexes indicate reduction of number of patches and edge effect, enlarging of patch area and, consequently, increasing of geometrical extent and coarse-grained landscape pattern.

Land Degradation by Erosion and its Economic Consequences for the Region of South Moravia (Czech Republic)

The quality of agricultural land fund in the Czech Republic is assessed via a valuation system based on the ecological-productive land evaluation. This system was established in the 1960-1980s after a complex survey of agricultural land. It provided integral information on the agricultural land quality and on the price of agricultural land parcels derived from their productive capacity. Starting from the 1990s, evidence in the database of Evaluated Soil-Ecological Units (ESEU) has been regularly updated. Intensive cultivation of wide-spaced crops, namely in extended, largely sloped land parcels, has resulted in degradation of land characteristics by the effects of erosion. The ESEU updating makes it possible to detect these changes and their quantification by differences in land price. This approach was applied to evaluate the economic impacts of erosion at two model localities in intensively exploited agricultural areas, in the region of the most productive soils of the Czech Republic. We compared the price per 1m 2 of land according to the land characteristics determined by the first land valuation with the current soil price based on the ESEU update. We also compared changes in the land characteristics. In the GIS environment, we established the mean long-term soil loss by erosion based on the original ESEU and compared it with the calculated soil loss based on the updated ESEU. The calculation method used was in accordance with the valid methodology for erosion calculation in the Czech Republic.

Priority Areas for Initiating Land Consolidations Related to Erosion and Water Retention in the Landscape, Czech Republic

Land consolidations represent a unique tool for managing the problems of the rural space. They help to settle the land property rights and meet the current requirements associated with the protection and formation of a stable, permanently sustainable rural landscape. In the Czech Republic, complex land consolidations have been completed in 1,965 cadastral areas out of the total 13,100, and in 2,134 more they are in the preparation phase (up to 1st September 2015). It means that about 60% of cadastral areas in CR still await land consolidation. Our study aimed to localize the priority localities (cadastral areas and regions) for preferential implementation of land consolidation. The authors selected three thematic factors to determine the risk of their occurrence in particular localities and, consequently, the need to initiate the land consolidation. The analysis is based on the assumption that the cadastral areas where land consolidations have been completed or are under way have already dealt with the above-mentioned risk factors or will do so soon. Therefore, such areas have not been included into our study. The key selected thematic factors relevant for the preferential implementation of land consolidation include: the risk of water and wind erosion in arable land, water management, and water retention in the landscape. For each of these three factors, a map of preferential localities (based on the degree of risk/suitability) was processed for initiation of land consolidation. At the same time, a simple multi-criteria analysis of the extent of the Czech Republic’s erosion (water and wind) has been prepared. The result of this analysis is the ranking of regions according to the degree of risk of erosion. The most vulnerable regions of the Czech Republic include Jihomoravský (South Moravian Region), Středočeský (Central Bohemia) and Pardubice.

Water Retention in a Small Agricultural Catchment and its Potential Improvement by Design of Water Reservoirs – A Case Study of the Bílý Potok Catchment (Czechia)

Abstract Water retention in the landscape is discussed in the context of conservation and improvement of both its productive and non-productive functions. We analysed the retention potential of a small agricultural catchment associated with the Bílý potok brook, investigating the possibility to improve its retention capacity and slow down the surface runoff, thus increasing the underground water resources. Method of curve numbers was used for that purposes. From results, it emerged that present maximum water retention in the Bílý potok catchment is 96.2 mm. It could increase by 101.3 mm in case of grassing about 20% arable land threatened by soil erosion. As next possibility to retain water from precipitations in landscape, capacity and transformation effect of reservoirs designed in master plans was analysed. The latest programming tools working in the GIS environment were used to assess the retention capacity of both the catchment surface and the reservoirs. Analysing master plans in the catchment, it was found that 16 designed water reservoirs (from 31) have a good potential to intercept water and transform flood discharges. In the result, priority for building of reservoirs was recommended according to their pertinence and efficiency in the studied catchment. Presented complex approach can be widely implemented, especially for better effectivity and cohesion of landscape planning and land consolidations processes.

Historical Changes in the Land Use Connected with Appropriation of Agricultural Land – Case Study of Cadastral Areas Dolní Věstonice and Modřice (Czech Republic)

Abstract The article focuses on the issue of agricultural soil sealing in the Dolní Věstonice and Modřice cadastres (South Moravian Region). Available data and map resources were used for this purpose (historical and up-to-date). Data was processed using manual digitalisation which helped to generate the needed map output. The decrease in area of agricultural land is analysed in individual periods starting in the year 1824 (source of data stable cadastre - the first half of the 19th century) until the present, and the sealing of different types of plots and soil kinds is assessed according to Evaluated Soil-Ecological Units (ESEU). In most cases, agricultural land sealing is associated with municipal expansion. To compare future development, potential (forthcoming) agricultural land sealing proposed within the valid landscape plans was also explored. Likewise, the overall price of sealed plots in both locations was calculated. The results show that there was a significant change in the use of both model territories between 1824 and the present. In Modřice, the area of the built-up area was changed from 16 ha (1824) to 409 ha (2016). The area of the site has expanded from 90% to agricultural land. The most significant change in this area is the development of builtup areas on agricultural land. In the model territory of Dolní Věstonice, the area of the built-up area increased from 16 ha (1824) to 48 ha (2016). The area of the site has expanded from 70% to agricultural land. Due to the construction of water reservoirs “Nové Mlýny”, the area of water bodies increased by 569 ha (during the period 1824- 2016). The water reservoirs occupy 65% of the cadastral area of Dolní Věstonice. The most significant change in landscape is the increase in water areas in Dolní Věstonice. Should this trend persist, an extensive reduction in agricultural soil and ensuing problems associated with sustainable agriculture, potentially also deficient food resources must be anticipated.

A universal meteorological method to identify potential risk of wind erosion on heavy-textured soils

Abstract The climate of Central Europe, mainly winter seasons with no snow cover at lower altitudes and a spring drought as well, might cause erosion events on heavy-textured soils. The aim of this paper is to define a universal method to identify the potential risk of wind erosion on heavy-textured soils. The categorization of potential wind erosion risk due to meteorological conditions is based on: (i) an evaluation of the number of freeze-thaw episodes forming bare soil surfaces during the cold period of year; and (ii), an evaluation of the number of days with wet soil surfaces during the cold period of year. In the period 2001–2012 (from November to March), episodes with temperature changes from positive to negative and vice versa (thaw-freeze and freeze-thaw cycles) and the effects of wet soil surfaces in connection with aggregate disintegration, are identified. The data are spatially interpolated by GIS tools for areas in the Czech Republic with heavy-textured soils. Blending critical categories is used to locate potential risks. The level of risk is divided into six classes. Those areas identified as potentially most vulnerable are the same localities where the highest number of erosive episodes on heavy-textured soils was documented.