SSS11.4

Raindrop driven erosion – what is in the black box ?

P.I.A. Kinnell

Faculty of Science and Technology, University of Canberra, Canberra, Australia

Many experiments applying rainfall to produce erosion on soil surfaces consider the inputs and outputs in a black box situation where little or no consideration is given to the actual mechanisms controlling erosion. It is well known that rainfall erosion is caused by raindrop impact and flow forces acting singly or together. Raindrops impacting directly or through surface water detaches soil material from where it is held within the soil surface by cohesion and inter-particle friction  and erosion occurs if the detached material is transported away from the site of detachment. The movement of detached material downslope may be in the air by splash or more importantly in surface water flows where raindrop impact may induce coarse sediment may to move when sediment transport normally associated with undisturbed flow does not occur. These transport processes vary in space and time during laboratory and field experiments. How this influences the amounts of soil loss during these experiments is the subject of  this presentation .

How to cite: Kinnell, P.: Raindrop driven erosion – what is in the black box ?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8548, https://doi.org/10.5194/egusphere-egu21-8548, 2021.

Mechanized vineyard floor tillage aims at minimizing negative impact of weeds on water competition and spread of pests and diseases without herbicide application. It includes tillage between vines, in the vine row, and in headlands around vineyard blocks. While there is an increased awareness from vine growers and scientists concerning water erosion, wind erosion and dust emission are largely unnoticed processes that have not been investigated yet. The emission of soil particles seems to be strongly associated to the working of the soil surface by means of (tracked) tractor. This impact may be particularly important on surfaces considered erosion stable due to vegetation or stone cover preventing soil from direct detachment by wind.

The row-tillage only underneath the vines is an important management practice in modern and in organic viticulture because of the strongly reduced soil disturbance compared with clearing of the complete vineyard floor area. We investigated tillage as a trigger for wind erosion and dust production on particularly inclined vineyards in this study.

Three different tillage tools in three combinations were tested on two different steep-slope vineyards by means of modified Wilson and Cook Sampler (MWACS): rotary hoe, disc plow, and finger weeder.

We measured eroded material on both sites for different states of soil moisture and wind intensity. The results suggest a relationship between particular tillage tool combinations and airborne substrate particles that correspond to the general mechanical procedure.

These first results for measurement of tillage-induced wind erosion and dust emission indicate a considerable potential of vineyards to release dust that is related to specific management device needs to be investigated by means of qualitative analysis, flux measurements and monitoring.

How to cite: Marzen, M., Iserloh, T., Porten, M., and Ries, J. B.: Measurement of wind erosion and dust emission triggered by different tillage tools, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9754, https://doi.org/10.5194/egusphere-egu21-9754, 2021.

The Mosel wine region (Rhineland-Palatinate, Germany) is the largest steep vineyard region in the world. Due to extreme slopes, tillage with heavy machinery, increase in extreme precipitation events, and new planting of vines, these vineyards are among the agricultural systems most affected by soil erosion.

As a result of viticulture since the Roman period and their special characteristics, almost all vineyard soils in the Mosel region are classified as Terric Anthrosols. These soils are characterized by a very high rock fragment content (mainly Devonian argillaceous schists and fluvial sediments) and a loose surface horizon over a compact one due to tillage or weathered parent material. This structure enables subsurface flows within the upper horizon, especially in periods of very high soil moisture.

There is a knowledge gap concerning the identification and quantification of transported soil particles in this subsurface flow. If these soil particles reach relevant amounts, superficial protective measures against soil erosion may be partially ineffective, and the soil degrades due to substantial loss of fine material. In consequence, there is a need to develop a method to determine this subsurface particle transport in situ.

In this study, a first experimental approach for assessing the occurrence of subsurface erosion of fine-grained soil particles within soils is presented. Using this experimental set-up, it is possible to prove the process of fine soil material transport as well as the development of sediment traps for in situ measurements.

The experimental approach consists of a sediment trap prototype, based on a drainage pipe, which is positioned into a test flume. The dimensions of this flume are 2.7 m x 0.9 m x 0.2 m (L x W x H). It is filled with material from a vineyard soil of the Mosel valley flanks. Water enters the flume from the upper end with the help of an 0.11 m high overflow. The sediment trap is 0.86 m long and has an 0.855 m x 0.4 m long side-cut-out where a mesh (mesh aperture 3 mm x 6 mm) is installed. It is connected to a separate drain where the water and eroded sediment are collected. This is analysed in the laboratory to quantify the amount and characteristics of the eroded material. Additionally, the total subsurface flow is measured by a drain at the lower end of the soil body for having a total mass budget of runoff and erosion.

The preliminary results show a clear correlation between the measured total subsurface flow and sediment transport with the ones collected with the sediment trap. The results suggest that this sediment trap prototype is clearly suitable to quantify the subsurface soil erosion. In the further course of the work, the sediment trap will be installed in situ in the vineyards to test its field applicability to determine valid subsurface erosion rates in vineyard soils.

How to cite: Kögler, L., Iserloh, T., Helmer, A., Steehouwer, E., Ruby, A., Seeger, M., and Ries, J. B.: Subsurface particle transport in coarse-grained vineyard soils – a laboratory flume experiment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4841, https://doi.org/10.5194/egusphere-egu21-4841, 2021.

Rainfall simulation experiments are widely used in soil science, geomorphology and hydrology research and teaching. Such experimental setups are particularly important in the study of rainfall-runoff, erosion and pollutant transport processes. Rainfall simulators have been applied within laboratory- and field-based studies and have the advantage of enabling controlled and reproducible rainfall events of varying intensity, duration and drop spectra. The flexibility and adaptability of rainfall simulators to examine diverse research applications of varying temporal and spatial scales means that hundreds of tailor-made rainfall simulator setups can be identified across the literature. Although it is beneficial for researchers to adapt their experimental designs to suit their specific research objectives, the diversity in the type, sizing, form, operation and methodologies of rainfall simulators ultimately results in complications when comparing results and outputs obtained between studies.

Currently, comparisons between studies can be very difficult, if not impossible, as the different measurement methods, artificial rainfall event characteristics and test conditions result in considerable difficulties when benchmarking results and findings obtained from rainfall simulation experiments. We recommend that the scientific community should establish a set of methodological procedures aimed at harmonising basic procedures in rainfall simulator-based studies in the fields of hydrological and geomorphological sciences. This would ensure that results obtained from different rainfall simulator studies and setups are harmonised, regulated and comparable. On the one hand, this process involves harmonising rainfall simulators design characteristics, whereas further steps should focus on measurement methods and metrics so results can be more readily compared.

This presentation highlights the inherit problems in benchmarking and comparing studies at present due to large variations in the way that researchers and institutions assess and quantify rainfall simulator performance and present results. Some degree of ‘standardisation’ of rainfall simulator approaches is needed. However, standardising approaches used within rainfall simulation does not allow researchers to adapt their experimental setups to suit their specific research needs, which is one of the key benefits of using rainfall simulators. Instead, ‘harmonisation’ (i.e. ensuring that the scientific community develop a set of regulated and comparable methodological procedures and best practices for use in rainfall simulator studies whilst still allowing some degree of adaptability for specific research practices) is required. Here we present a series of harmonisation procedures, which should be developed to ensure that rainfall simulators are designed and constructed to allow for harmonisation, as well as suggesting a series of steps towards harmonising the methods and metrics used to quantify and compare experimental results.

With these objectives in mind, we aim to stimulate the discussion and enhance understanding of the difficulties and requirements of rainfall simulator based experimental research, namely by creating a platform that embraces and consults the International research community across multiple research facilities and institutes. This presentation will kick-start discussions (via web seminar sessions beginning in Summer 2021) leading up to a future international symposium addressing and acting upon these issues and disseminating the findings of this consultation period (Spring/Summer 2022 in Coimbra, Portugal). Everyone is invited to join this step towards harmonisation in rainfall simulation.

How to cite: Iserloh, T., Isidoro, J. M. G. P., de Lima, J. L. M. P., Marzen, M., de Lima, M. I. P., Green, D., Seeger, M., and Ries, J. B.: Moving towards harmonisation in rainfall simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5667, https://doi.org/10.5194/egusphere-egu21-5667, 2021.

Vineyards are vulnerable to soill loss due to the several inherent factors highly discussed in the literature. A lot of research is being carried out on this topic and hundreds of experiments were conducted around the world in past decades. The use of rainfall simulators is very extensive with prominent results; however, the use of different scales is scarce in exact places but using different plot sizes. Small (1-4 m²) and big plots (>4 m²) can detect the initiation of specific processes such as surface runoff and initial of soill particle detachment. However, mechanisms such as connectivity, sedimentation or linear erosion differ among plot sizes. Also, the size, high water consumption and time-consuming of the big rainfall simulator makes its use something scarce. Therefore, the main goal of this research was to compare the big and small rainfall simulators and the obtained results considering the continuous development of various rainfall simulators on the CTU’s Department of Landscape Water Management (Prague, Czech Republic). The small rainfall simulator with 1x1 m plot and the big one covering two experimental plots of 8x1 m size were used next to each other in a conventional vineyard in the viticultural region of Moravia. The results showed different processes both of them key to understand from a holistic point of view the inititaion of soil erosion processes in vineyards.

This study has been supported by the Grant Agency of the Czech Technical University in Prague, grant No. SGS20/156/OHK1/3T/11 and the Project QK1910029.

How to cite: Neumann, M., Kavka, P., Devátý, J., Strouhal, L., Tejkl, A., Stašek, J., Kubínová, R., and Rodrigo-Comino, J.: Rainfall simulation experiments in vineyards comparing two different plot scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5031, https://doi.org/10.5194/egusphere-egu21-5031, 2021.

Research of evaporation height is curtailing for measuring of the water balance in small catchments and for proper and efficient running of irrigation systems.

Ongoing project to develop the simple and reliable, easy to reproduce evaporation measuring device. Core part of the device are measuring of the water level in field in cheap form. 3D printed design in combination with open-source cheap electronics is utilised. Methodology and results of the ongoing research project will be presented. Project investigates the affordable and simple technical measures that have a potential to increase the number of opportunities for the measuring of evaporation.

Continuously the theories are developed and tested, subsequently conclusions are implemented into the next generation of the device. Seven generations of 3D printed part have been done, and now the research focus on the water supply part of the device. Durability and reliability of the device is tested in field, in three locations. All plots are monthly checked by research staff and data is saved and later compared with data measured by device. Refilling of the evaporation pan is done automatically.

Prototype seven uses the experience of all previous prototypes. The construction is equipped with 50 individual electrodes, each electrode is 1 mm shorter than previous. Another 2 electrodes serve as a negative collector. The total measuring range is 50 mm. The whole structural part of prototype seven is designed as a printout on a 3D printer, electrodes are printed from conductive material. Above the electrodes there is a printed circuit board carrying the microelectronics control.

The principle of measurement consists in measuring of capacity of capacitors joined in parallel. Charge goes through the capacitors to needles, then through water environment to negative collector needle and to negative terminal. Because different lengths of the needles, change of water depth, changes the number of submerged needles and thus number of connected capacitors. So, water depth is directly related to measured capacity.

A commonly used evaporation unit is mm of water column per day. It is therefore necessary to analyze a long time series, at least longer than one day, and covering the entire day from 00:00 to 23:59. On the other hand, there is need for redundant data, so measuring step six hours is chosen.

The sites are the grounds of the CTU Faculty of Civil Engineering in Dejvice, the experimental sites of the CULS in Prague Suchdol and the Water Research Institute in Prague Podbaba.

The research is funded by the Technological Agency of the Czech Republic (research project TJ02000351 - Development of Tools and Methods Improving Estimation of annual Evaporation Balance).

How to cite: Tejkl, A. and Kavka, P.: Next generation of Automated Low Investment Cost Evaporometers (ALICE), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7236, https://doi.org/10.5194/egusphere-egu21-7236, 2021.

In this contribution the particle size distributions of the soil sediment obtained from soil erosion experiments were analysed. All the tests were done on arable topsoil’s, separately the size distribution of the soil aggregates and individual soil particles were evaluated. Soil erosion was initiated under the controlled conditions. CTU Prague laboratory rainfall simulator and field laboratory in Jirkov were used for this research. 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 – 34°, slope length 4 m).
During each experiment, eight samples were collected. Four samples were collected during the first experimental rainfall. For the next ten days, the container was kept aside the rainfall. Afterwards, the raining with the rainfall simulator on plot (which now had different initial condition compared to the plot during the first experimental rainfall as the plot already contained erosion rills from the previous episode) has been resumed and another four samples were collected.
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) – Enkamat 7010, and 7020, Biomac-C, coir fibres K700 and K400, jute, Macmat 8.1, mulch, hay, nonwoven, fortrac 3D and triangle. The influence of RECPs to the particle size distribution was investigated.
Laser diffraction has been selected as a method to determine particle size distribution and device Mastersizer 3000 was used. By the comparison of the particle size distribution, of more than five hundred samples, the different response to the soil erosion mechanism and the influence of external factors (slope of the experimental plot, initial condition and presence of RECPs) on the particle 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.
This research is funded by the TH02030428 - „Design of technical measures for slopes stabilization and soil erosion prevention” and by the International CTU grant SGS20/156/OHK1/3T/11.

How to cite: Kubínová, R., Kavka, P., Neumann, M., and Kubát, J.-F.: The influence of different roll erosion control products to the particle size distribution of the soil sediment eroded on artificial slopes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9417, https://doi.org/10.5194/egusphere-egu21-9417, 2021.

Determining the particle size is a current problem in many earth science sub-disciplines. Particle size distributions of sediments provide insight into the physicochemical environment, transport, accumulation and accumulation of particle formation, and post-deposition transformation processes. Therefore, granulometric proxies are widely used in paleoclimate research and many soil properties depend on their particle size distribution. Several studies are available comparing different laser diffraction devices, optical theories, and optical settings. Ignoring limitations of laser diffraction technique can result in poorly comparable granulometric data sets, however, inadequate chemical pretreatment procedures are also limiting factors, which are often overlooked. In this study, we examined different sediment types from various geomorphological environments from the Carpathian Basin: lake, eolian, fluvial sediments and paleosols. Our aim is to review and create a reliable methodology for laser diffraction particle size analysis and optical particle shape investigations. The widely used pretreatment methods (total of 13) were compared. The results showed that the samples with different textural parameters were differently affected by the preparation procedures. Compared to the silty textured loess and paleosol samples, applied techniques did not cause substantial changes of results of sandy materials, although the duration and the applied amount of the reagent had some impact on the grain size data.  Using cluster analysis, the various pretreatment methods could be separated from each other proving that these procedures are able to create substantially different grain size datasets. Shape parameters of the particles were also modified by the pretreatment methods, significant changes could be observed in the circularity, convexity characteristics. The study is supported by the ÚNKP-19-3 New National Excellence Program of the Ministry for Innovation and Technology. The support of the National Research, Development, and Innovation Office (projects NKFIH KH130337 and K120620) is gratefully acknowledged.

How to cite: Gresina, F., Szalai, Z., and Varga, G.: Chemical pretreatment effects on grain size results of clastic sediments and soils, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13109, https://doi.org/10.5194/egusphere-egu21-13109, 2021.

Rain throughfall under vegetation is determined by characteristics of the vertical structure and the associated plant traits. It goes both ways: A protective layer of ground covering vegetation or leaf litter can decrease throughfall kinetic energy (TKE), whereas the formation of large drips in the canopy layers has been found to increase TKE. Abstracting the three-dimensional vegetation structure into usable quantitative metrics is challenging, and therefore these processes have not yet been sufficiently integrated into spatial erosion models. The vegetation splash factor (VSF) was designed to close this gap (Senn et al. 2020, DOI: 10.1002/esp.4820). The VSF quantifies the influence of vegetation on TKE and can be calculated from aerial lidar point clouds. In the first step, we derive the vegetation cover in a voxel space, which then allows modelling the proportional contribution of drips per layer to reach the ground. Hence, the approach is strictly based on the 3D structure rather than conventional forestry parameters, e.g. crown diameter or leaf sizes. Here, we present the result of the first application of the VSF in a small scale field study using splash cup measurements to validate and refine the concept.

We implemented the experiment in a mixed-broadleaf forest near Bretten, Germany with a beech and an oak-dominated plot to cover a variety of vertical forest structure configurations and a diverse composition of species. Each plot comprised two transects of ten splash cups to measure sand loss - as a proxy for TKE - during six individual rainfall events. In addition, we used micro-scale runoff plots to determine the effect of soil covering layers such as leaf litter or biological soil crusts in comparison to bare soil. The VSF was calculated in R with a voxel resolution of 0.5 x 0.5 x 0.25 m using a UAV lidar dataset. 

Initial results from the splash cup measurements showed that young oak induced about 70 % higher TKE than adult beech trees. Among the individual cup positions, the lowest energy values were measured without canopy influence as freefall kinetic energy (FKE), TKE at positions with an intermediate young growth and shrub layer showed medium values. In near-trunk and mid-positions without intermediate layers, we measured TKE values more than twice as high as FKE. This resulted in significant sediment removal beneath the tree layer when the ground covering vegetation layer was removed, which is in accordance with studies from other ecosystems. Grouped according to these conventional vegetation structural criteria, we found that the calculated VSF values clustered around similar values and correlated with sand loss from splash cups. From these initial results, we assume general suitability of the VSF to reflect the influence of vegetation structure on TKE. Further, more detailed analysis will now be done to adjust and calibrate the VSF model to produce more indicative results. The preliminary findings presented here will be further expanded to be presented at vEGU21.

How to cite: Senn, J. A., Seitz, S., Fassnacht, F. E., Hosseini, Z., and Schäfer, J.: Time for 3D: UAV-based lidar for modelling splash erosion under vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7816, https://doi.org/10.5194/egusphere-egu21-7816, 2021.

There is still uncertainty in determining vegetation cover and management factor (C factor) for Universal Soil Loss Equation (USLE). Data we use today are often outdated, not specific and not representing local conditions. Current technologies in agriculture and recent crop varieties substantially vary from processes known during USLE (RUSLE) development.

Use of a rainfall simulator on a defined field crop is one way to obtain data for vegetation protection effect. Simulated rainfall is applied on experimental field with crop and bare soil as a reference. Plot size is 8x2 m and runoff and sediment transport is measured. Soil loss ratios are measured for three crop-development stages. Pre-sowing and post-harvest phases are measured as well. All measured data give information about soil protection for the whole season. In the span of 5 years, we have conducted over 340 field experiments on 15 typical, but also newly used crops and various management practices. The results are used in soil erosion and sediment transport analyses or models’ calibration. Metadata of experiments and results are added into a complex and public available database.

The contribution was prepared in the frame of projects No. QK1920224 (Possibilities of anti-erosion protection on farms to avoid the use of glyphosate), and H2020 SHUi (Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping systems).

How to cite: Stašek, J., Krása, J., Roudnická, A., Dostál, T., Mistr, M., and Devátý, J.: Experimental assessment of soil protection by vegetation for current crops and for up-coming EU glyphosate ban, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9451, https://doi.org/10.5194/egusphere-egu21-9451, 2021.

Many studies have focused on soil erosion in unmanaged Japanese cypress plantations because the sparse understory vegetation and litter covering the forest ground enhance soil erosion. Many studies also indicated that soil erosion and overland flow have large spatial variation. However there are less studies focusing on sampling strategy to obtain the slope scale soil erosion and overland flow in forested slope area. In this study, soil erosion, litter, and overland flow measurements were conducted over 14 months (March 2016 to April 2017) to identify the spatio-temporal variation and examine the optimal sample size in an unmanaged Japanese cypress plantation located in Aichi Prefecture, Japan. We used small-sized traps to collect sediment, litter and overland flow simultaneously. These traps with dimensions of 0.15 × 0.25 × 0.20 m (height × width × depth) was made by stainless- steel. Each trap was connected to a storage plastic tank installed downslope of trap to store the overland flow. To capture sediment and litter, the outlet of downslope-facing trap was wrapped by 1 mm mesh. To estimate the sediment that passed this mesh, water stored in the plastic tank was sampled to obtain the sediment concentration. Fifteen traps were installed in line along the bottom of a 15-m wide slope. The sampling interval was approximately 1 month. The range across all traps in terms of soil erosion was 79.2 to 596.8 g m^-1, while for litter it was 132.8 to 246.4 g m^-1 and for overland flow, 42.0 to 612.4 L m^-1. The temporal coefficient of variation of soil erosion and overland flow was highest during dry seasons, while smaller during wet seasons. These results indicated that soil erosion and overland flow had larger spatio-temporal variations as compared to litter. To examine the relationship between sample size (number of traps) and potential errors caused by the spatio-temporal variation of soil erosion, litter and overland flow measurements, stratified Monte Carlo random sampling was performed. This random sampling analysis showed that the rate of decrease in spatio-temporal variation became moderate as the sample size increased beyond six. This result indicated that the optimal sample size was five, the total width of which was equivalent to about 8% of the monitored slope width.

How to cite: Sato, T., Tanaka, N., Nainar, A., Kuraji, K., Gomyo, M., and Suzuki, H.: Soil erosion and overland flow in Japanese cypress plantations: Spatio-temporal variations and a sampling strategy., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15740, https://doi.org/10.5194/egusphere-egu21-15740, 2021.

The endemic argan tree (Argania spinosa) in Morocco, which is the source of the valuable argan oil, forms open-canopy forests that are highly degraded due to overgrazing, illegal cutting of firewood and the expanding intensive agriculture. Because of the high grazing pressure young sprouts cannot establish themselves, reforestation measures are often unsuccessful and the bare areas between the isolated trees are expanding. In a previous study, we could already show that these intertree areas are more degraded than the areas under the trees, regarding various soil parameters as well as their erodibility and infiltration capacity.

The spatial extent of argan trees on soil quality from the trunk to the intertree area is so far unknown. Hypothetically, the tree influences the soil of the intertree area by wind drift of tree litter and soil material towards the East, i.e. main wind direction, and downhill by runoff and erosion processes of soil material downslope. Tree shadow in the hot midday and afternoon sun should have positive influences on soil moisture in northern or northeastern directions. To test this hypothesis, we took 424 soil samples around 31 argan trees in four directions, uphill, downhill and in both directions parallel to the slope towards the nearest neighbouring tree in that direction. Samples along these transects were taken near the trunk, just inside and just outside the area covered by the tree crown and in the intertree area in the middle between two trees. The soil samples were analysed for various soil parameters (C/N, percolation stability, electrical conductivity, pH, soil moisture).

The first results show that the influence of the trees is not limited to the crown-covered area but for some trees extends further into the intertree area in specific directions according to the hypothesis (East due to wind drift, North due to shade and downslope due to slope runoff). For other trees the influence of the trees does not even encompass the whole crown-covered area, where we found similarly lower soil quality as for the bare intertree areas. These differences may result from the degradation state of the tree as well as from the different characteristics of the study areas. Understanding the way argan trees influence their surrounding intertree areas would enable structured reforestation measures with a higher chance of successful rejuvenation of the argan forest.

How to cite: Kirchhoff, M., Romes, T., Marzolff, I., Seeger, M., Aït Hssaine, A., and Ries, J. B.: Spatial patterns of argan-tree influence on soil quality of intertree areas in open woodlands in South Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2252, https://doi.org/10.5194/egusphere-egu21-2252, 2021.