Václav David

Historical ponds of the Czech Republic: an example of the interpretation of historic maps

ABSTRACT The paper presents a map of historical ponds of the whole Czech Republic which was created on the basis of the 2nd Military Survey (1: 28,000) from the period 1836 to 1852. This source was selected with respect to its age, precision, validity and accessibility at the Czech National Geoportal via the Web Map Service. All water areas, which had existed in the 2nd Military Survey within the current Czech Republic, were identified on this basis and vectorised in the Geographic Information System. Historical ponds larger than 0.5 ha were then picked from this layer, complemented with other attributes and analysed in combination with the current geodata (occurrence of pond, prevailing land use of extinct ponds, etc.). The resulting map may serve as a measure for potential attempts at restoring some extinct ponds, out of which over 3400 ponds larger than 15,500 ha have been discovered. This map source may be practically applied in Spatial Planning and in particular measures taken against changes in the global climate, specifically in the Czech Republic against droughts. The map source may be utilised by state authorities or local administrations.

Determining the protective effect of agricultural crops on the soil erosion process using a field rainfall simulator.

In this paper the data measured by application of the MDS NZ2 field rainfall simulator have been used to demon strate the effect of vegetation cover on surface runoff generation and soil loss. The results of 15 experiments for two crops (oats and wheat) are presented. Canopy cover and the leaf area index are used to describe the vegetation development. Measured soil loss decreased with growing vegetation significantly from the maximum values 74.7 g/min for oats (38.4 g/min for wheat) to 0.4 g/min (1.5 g/min respectively) from the experimental plot of 16 m 2 . Thus, this work clearly demonstrates the positive effect of canopy development on soil loss. However, the ef fect of the developing cover on the surface runoff generation was not significant.

Analysis of Flood Hydrographs in Order to Predict the Shape of Their Falling Limbs

This paper presents preliminary analyses carried out in order to assess the possibility to treat a small simple catchment as linear reservoir when modeling the runoff from a precipitation event. This analysis was carried out for the catchment of Cerna Desna stream to the profile Jezdecka. The applicability of linear reservoir concept was tested by calculating the recession constant values for hydrographs falling limbs which were then evaluated in a statistical way. Specifically, five events were selected for the detail analysis. The results indicate that the linear reservoir concept can be applied in this case to predict relatively well the discharges in next 48 h. However, the results also show that there are limitations in the application of linear concept and that the introduction of non-linear reservoir could improve the prediction results.

Geophysical Evaluation of the Inner Structure of a Historical Earth-Filled Dam

Small earth dams usually lack the detailed seepage monitoring system that would provide high resolution data on changes in seepage flow. Alternative solution is monitoring of the temperature and electrical resistivity in the body of the dams. Geophysical methods are useful techniques for a non-destructive exploration of the subsurface. We have utilized the combination of electrical resistivity tomography (ERT), ground penetrating radar (GPR) and multi-depth electromagnetical conductivity meter (CMD) techniques to observe the inner structure, especially internal failures, of the historical earth-filled dams. Longitudinal and transversal profiles of four typical fishpond dams in the Czech Republic were measured within this research. The dams were constructed as early as in the 15th century, some of them went through minor reconstruction. The aim of the application of geophysical methods for investigation of old fishpond dams was to detect and localize the boundary of the dam foundation, new earth material from the reconstruction works, cone of water depression, technical objects location, potential internal erosion, cavities, inhomogeneity in the water content pattern and any other anomalies. The primary results show that the ERT is suitable to observe the dam stratification, dam foundation, bedrock below the dam and large anomalies. GPR is suitable for small objects and anomalies detection in the shallow depths.

Close Range Photogrammetry and Thermal Imagery in Monitoring of Soil Moisture in Dam Structures of Historical Fishponds

Degradation of reservoir dams can lead to water percolation through dam structure. Here, close-range photogrammetry and UAV (Unmanned Aerial Vehicle) thermal imagery can be used to monitor differences in dam moisture. The article presents a study of the dam of Podvinak Fishpond (Czech Republic). The TDR (Time Domain Reflectometry) data (soil moisture), the Theta probe data (soil moisture), and the temperature data of the dam top profile and the grassed area below the dam were compared. Analysis focused on the comparison between sampled data, and UAV data obtained by Optris TIM 450 (Portsmouth, USA) and Flir Tau2 336 (Wilsonville, USA) IR cameras. Based on the study, the spectral resolution, the accuracy of the results, and the reliability of both UAV monitoring systems is similar.

Floodplain retention capacity assessment for Lužnice river

One of main topics of interdisciplinary project NIVA – Water Retention in Floodplains and Possibilities of Retention Capacity Increase is the assessment of flood wave transformation in the floodplain. The project focuses on broad field of floodplain ecosystem services and flood mitigation is a phenomenon which is researched by the team from Czech Technical University from different points of view and using different methods. Despite the fact that the main influence on flood wave transformation is flow retardation due to the flow velocity decrease, the retention in surface depressions within floodplain has been analyzed to get better overview of whole transformation process. Detailed digital relief model (DRM) has been used for given purposes to be able to analyze terrain depressions volumes. First, the methodology of analysis was prepared and tested on artificial surface. This surface was created using random raster generation, filtration and resampling with final resolution of 1,000 × 1,000 units and height of maximum 10 units above datum. The methodology itself is based on analysis of areas inundated by water at different elevation levels. Volume is then calculated for each depression using extraction of terrain elevations under corresponding water level. The method was then applied on the area of Lužnice River floodplain section to assess the retention capacity of real floodplain with natural character which usually means higher surface retention capacity in comparison to trained rivers. Results obtained from above mentioned analysis applied on Lužnice river are presented in this paper. The importance of floodplain retention capacity for flood transformation is low as results from obtained values.

Sediment transport and water quality in Máchovo Lake (Czech Republic)

Sediment transport and water quality in Máchovo Lake (Czech Republic) Máchovo Lake is a historical reservoir founded by Czech King Charles IV. in 14th century. Located in northern part of central Bohemia it has been widely used for recreation purposes for many decades (or even centuries). Its catchments (ca 100 sq km) consist of intensively used agricultural land (ca 25% of area) and of large forested area under nature protection. Several other lakes (ponds) are chained on the two reservoirs inlets. Irrespective of its great recreation potential Máchovo Lake is one of the Bohemian lakes known for its problems with eutrophication and water quality. The project was set up to point out sources of nutrients and to search for proper solutions. Sediment loads in every lake within the catchments were measured and sampled in order to quantify the nutrients and other pollution. Point and non point sources of phosphorus and other nutrients were searched. Sediment transport within catchments was modelled using WaTEM/SEDEM model. Interestingly, the water quality in the particular ponds varies significantly even though each one of several hundred years old ponds is heavily silted. Soil erosion protection measures within catchments were proposed altogether with flood protection measures in the stream valleys and waste water treatment facilities in surrounding villages. Setting up water quality sampling devices in selected stream profiles was tested and designed. The continual proper management should lead to water quality improvement. Transport sedymentu i jakość wody w Jeziorze Mahovo (Republika Czeska) Położone w północnych Czechach Jezioro Máchovo jest zbiornikiem dla celów rekreacyjnych zbudowanym w XIV wieku przez czeskiego króla Karola IV. Jego zlewnia o powierzchni 100 km2 jest w 25% intensywnie użytkowana rolniczo, a pozostały zalesiony obszar podlega ochronie. Jakość wody i eutrofizacja wód jeziora oraz towarzyszących mu silnie zamulonych stawów stanowi poważny problem ekologiczny. Celem badan było określenie punktowych i powierzchniowych źródeł dostawy składników pokarmowych i rozwiązanie tego problemu. Do oceny dostawy sedymentu zastosowano WaTEM/SEDEM model. Została zaproponowana przeciwpowodziowa i przeciwerozyjna ochrona gleby przed erozją oraz gospodarka ściekami w obrębie zlewni. Działania te powinny doprowadzić do polepszenia jakości wody.