In this study, the particle size distribution (PSD) of the soil sediment from topsoil obtained from soil erosion experiments under different conditions was measured. Rainfall simulators were used for rain generation on the soil erosion plots with slopes 22°, 30°, 34° and length 4.25 m. The influence of the external factors (slope and initial state) on the particle and aggregate size distribution were evaluated by laser diffractometer (LD). The aggregate representation percentage in the eroded sediment was also investigated. It has been found that when the erosion processes are intensive (steep slope or long duration of the raining), the eroded sediment contains coarser particles and lower amounts of aggregates. Three methods for the soil particle analyses were tested: (i) conventional–sieving and hydrometer method; (ii) PARIO Soil Particle Analyzer combined with sieving; and (iii) laser diffraction (LD) using Mastersizer 3000. These methods were evaluated in terms of reproducibility of the results, time demands, and usability. It was verified that the LD has significant advantages compared to other two methods, especially the short measurement time for one sample (only 15 min per sample for LD) and the possibility to destroy soil aggregates using ultrasound which is much easier than using hexametaphosphate.
Soil erosion is recognized as a threat to humankind and to natural ecosystems when sustainable limits are exceeded. Several researchers have used various tools, such as rainfall simulators, to assess extreme rainfall events and non-sustainable soil management practices. However, combinations of two different devices of different sizes has not been tested before, especially in vineyards. The aim is to verify whether plot size, connectivity processes and rainfall distribution affect the activation of soil erosion. In this research on soils cultivated with vineyards in the Moravia Region in the south-eastern part of the Czech Republic, we have performed various rainfall simulation experiments with a small device (1 × 1 m) and with a large device (8 × 1 m). Our results show that the surface runoff was approximately 30% higher on the small plot than on the large plot. The large rainfall simulator produced sediment concentration that was up to 3 times higher, and soil loss that was up to 1.5 times higher, even when the surface runoff was 30%–50% lower for the large rainfall simulator. We therefore conclude that there is a clear influence of surface length and plot size on surface runoff, soil loss and sediment concentration activation. When planning their experiments, researchers need to consider that the type of device can have a drastic influence on the final results. Two devices subjected to the same rainfall intensity (60 mm h−1) can produce very different results, e.g., depending on plot size and kinetic energy. Our results can be effectively used to plan soil protection measures and to inform local authorities about areas prone to flooding and about loss of sediments.
<p>Soil erosion is a long-term problem that causes the degradation of the earth's surface depending on geomorphological and climatic conditions. Adverse combinations of these conditions can create situations where not only sheet erosion occurs, but also rill processes begin to occur due to the concentration of surface runoff. Erosion processes become undesirable and dangerous when they occur on construction sites. The presented project is basically focused on the effectiveness of protective geotextiles against soil erosion, but processes related to sheer and rill erosion were also investigated. The research was carried out on experimental plots of 4x1 meters, which were placed in the outdoor laboratory in Jirkov. These three plots were set at slopes from 22&#176; to 34&#176; and artificial rain was simulated on them using a rainfall simulator. A second experimental area of &#8203;&#8203;the same size was available at the laboratory rainfall simulator at the CTU in Prague, where a modern facility was created for the purpose of soil erosion testing on steep slopes. This device can create slopes up to 40&#176;.</p> <p>The photogrammetric method &#8222;Structure from Motion&#8220; was used for monitoring soil surface before and after each simulation. Orthophotos and digital elevation models were compared with each other to get digital elevation models of difference. Calculation of the ratio between sheet and rill erosion was done by manually creating rill polygons and by calculating the volume changes above the polygons of these rills and over the whole surface. According to preliminary results on these 4 m long slopes, the rill volume represented approximately 30 % compared to the overall volume change.</p> <p>Shifts of stabilizing natural geotextiles by surface runoff and eroded material were also monitored using photogrammetric methods. Deformations and displacements were measured from differences in the detailed images before and after the simulation. Transversal veins and their shift along the slope were evaluated.</p> <p>This research is funded by the TA CR &#160;- TH02030428.</p>
<p>It this contribution partial results of the project, which is focused on hydrological modelling as a tool for designing small water management construction and soil conservation measure and in the landscape are presented. For the hydrological response, design rainfall and the initial condition, the current state of the river basin as well as the characteristics of the area under consideration are important. For the hydrological response, design rainfall, the current conditions of the catchment area as well as the characteristics of the solved area are important.&#160;</p><p>Design precipitation in relation to initial conditions (soil moisture and surface condition) is one of the project goals. This data are important for hydrological modelling that is a tool for designing water management measures on small watercourses and in river basin areas is relevant for catchment size where long-term measurements and possible analogy cannot be used. The design of small hydrotechnical buildings based on hydrological modelling is used for catchments up to the area of &#8203;&#8203;5 km2.</p><p>Basic categorization of small catchments in the Czech Republic is presented. At present, the Czech catchments are categorized into four levels. From the main river catchment to the catchment of the category IV. order (small catchments). There are considerable differences in size in the fourth category. From catchment areas of over 20 km2 to supplementary catchment areas of less than 1 km2. The categorization of these catchments in terms of their potential hydrological response is described in the past. For the categorization of the territory of the Czech Republic at the level of small catchment areas in terms of hydrological response, the different size of the area is one of the hardly definable parameters.</p><p>For these reasons, the project addresses also the delimitation of small catchments in the Czech Republic, which fall into the category of areas up to 5 km2 and significant areas outside the watercourse and their subsequent classification in terms of possible hydrological response. The activities were in this ongoing project focused on delimitation of these catchments and research of suitable data for their classification.</p><p>Detailed model of terrain in the resolution 5x5 m and watercourse layer were used as input data for delimitation of small catchments. ArcGIS tools and Python scripting language were used for processing. As it is a relatively large data set, the following analyses were gradually repeated for the catchment III. order with the extension of the boundary, so as to ensure possible discrepancies between the delimitation of the basin and the distribution boards defined on the basis of a detailed terrain model.</p><p>Nine categories were selected as significant areas ranging from contributing areas of 0,3 to 5,5 km2. In the category of the smallest catchments (categories from 0,3 to 0,7 km2) there are over 70 thousand areas defined in the Czech Republic. In the category from 4,5 to 5,5 km2 there are over 4 thousand catchments. A categorization both for individual classes and overall for the territory of the Czech Republic according to the largest contributing area is presented.</p>
<p>In this contribution the grain size distributions of the soil sediment obtained from soil erosion experiments were analysed. All the tests were done on arable topsoil&#8217;s, separately the size distribution of the soil aggregates and individual soil particles were evaluated. Soil erosion was initiated under the controlled conditions in the laboratories. The rainfall was artificially generated with use of a nozzle type rainfall simulator. The sediment transported due to the surface runoff and rill erosion was collected from the discharge of the inclined soil erosion plots (slopes 20 &#8211; 34&#176;, slope length 4 m).</p><p>The soil sediment was collected in four sampling times. The first and the second were collected in fifteen and thirty minutes from the beginning of the simulation, then followed fifteen minutes long pause without raining and then the simulation continued and soil samples were collected again in fifteen and thirty minutes from the beginning of the rain. After ten days long pause whole process were repeated at the same experimental plot contains rills from previous simulation. Experimental plots were vertically divided into two parts. On one part was an eel and on the second part were different types of rolled erosion control products (RECPs) &#8211; Enkamat 7010, Biomac-C, coir fibres K700 and K400, jute, Macmat 8.1 with soil, mulch, hay and nonwoven. The influence of RECPs to the grain size distribution was investigated.</p><p>Laser diffraction has been selected as a method to determine grain size distribution and device Mastersizer 3000 was used. By the comparison of the grain size distribution, of more than five hundreds samples, the different response to the soil erosion mechanism and the influence of external factors (experimental plot slope, sampling time from the surface runoff and presence of RECPs) on the grain size distribution and soil aggregates content in eroded sediment were investigated. It has been found that both the particle size and aggregates size distribution of the eroded sediment changes considerably in time.</p><p>This research is funded by the TH02030428&#160;- &#8222;Design of technical measures for slopes stabilization and soil erosion prevention&#8221;.</p>
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