TLS-recorded massive bedrock erosion of a hyperconcentrated flow in an Alpine Gorge: approaches to modelling the event (Höllentalklamm, Germany)

2021 ◽  
Author(s):  
Verena Stammberger ◽  
Benjamin Jacobs ◽  
Michael Krautblatter
Keyword(s):  
Morphological Changes ◽  
Precipitation Event ◽  
Rheological Parameters ◽  
Data Set ◽  
Erosion Rates ◽  
Erosion Processes ◽  
Bedrock Erosion ◽  
Hyperconcentrated Flow ◽  
The Impact ◽  
Modelling Approaches

<p>High-intensity precipitation events and the resulting extreme discharges in mountain torrents are immensely dangerous and destructive hazards that can put lives in danger and cause expensive damages to infrastructure. There is a high probability that further changes in climate will favour the genesis and therefore increase the frequency of such extreme events. Nevertheless, there is a pronounced desire to experience breathtaking mountainous landscapes, especially when easy accessible. An example is the Höllental gorge (between 1032 and 1062 m a.s.l., Wetterstein mountains, Germany), a key touristic attraction in the region with up to 100k visitors per year. Especially for such highly frequented places, the knowledge and comprehension of possible risks from hydrological and geomorphic hazards is crucial. With this in mind, we are reconstructing and discussing possible modelling approaches of a recent event of a hyperconcentrated flow through the gorge.</p><p>In June 2020 a local extreme precipitation event between 50 and 60 mm/h caused a rapid accumulation of the surface runoff due to the steep slopes of the Höllental (inclination of ø 110%). Secondary sediment storages were mobilized and transported to the main channel where a hyperconcentrated flow developed at the beginning of the gorge. Depending on the percentage of transported sediment in the flow, temporary transitions to a debris flow were possible. Throughout the ravine, massive forces reshaped the rock walls and the channel bed by particle erosion, shearing and relocation of boulders up to 20 m<sup>3</sup>.</p><p>In this study we present a comparison of two terrestrial laser scan campaigns, the first two weeks prior to the event and the second just five days after. We were able to accurately calculate the morphological changes along the sides of the channel and obtained a unique data set for bedrock erosion rates due to the impact of a hyperconcentrated flow. We mapped the flow height throughout the whole gorge by identifying the visible transition of undisturbed to roughened rock surfaces. DEM difference calculation upstream allows to determine the erosion and deposition heights as well as the corresponding volumes. Additionally, electrical resistivity tomographies reveal the thickness of (still) available sediment upstream.</p><p>Here we discuss possible numerical and analytical modelling approaches and analyse preliminary results. We aim at coupling the observed erosion rates to calculated velocities of a model that integrates the complex topography as well as the rheological parameters of the flow. A calibration of the model will be achieved with the mapped flow height in the gorge. Due to the complexity of the gorge, a frequently used numerical simulation as well as a analytical open-channel flow model will be analyzed and compared.</p><p>This study presents a unique dataset of effective erosion rates with records collected pre- and post-event. The results contribute to strongly improve the understanding of the flow dynamics in hyperconcentrated flows and give unparalleled information about erosion processes in narrow bedrock channels.</p>

A multi-decade assessment of the impact of large fire events on sediment redistribution using LAPSUS - the Águeda catchment, north-central Portugal

2021 ◽  
Author(s):  
Dante Föllmi ◽  
Jantiene Baartman ◽  
João Pedro Nunes ◽  
Akli Benali
Keyword(s):  
Soil Depth ◽  
Spatial Scales ◽  
Fire Severity ◽  
Sediment Dynamics ◽  
Land Uses ◽  
Erosion Rates ◽  
Erosion Processes ◽  
Sediment Redistribution ◽  
Central Portugal ◽  
The Impact

<p><strong>Abstract</strong></p><p>Wildfires have become an increasing threat for Mediterranean ecosystems, due to increasing climate change induced wildfire activity and changing land management practices. Apart from the initial risk, fire can alter the soil in various ways depending on different fire severities and thus post-fire erosion processes are an important component in assessing wildfires’ negative effects. Recent post-fire erosion (modelling) studies often focus on a short time window and lack the attention for sediment dynamics at larger spatial scales. Yet, these large spatial and temporal scales are fundamental for a better understanding of catchment sediment dynamics and long-term destructive effects of multiple fires on post-fire erosion processes. In this study the landscape evolution model LAPSUS was used to simulate erosion and deposition in the 404 km<sup>2</sup> Águeda catchment in northern-central Portugal over a 41 year (1979-2020) timespan. To include variation in fire severity and its impact on the soil four burnt severity classes, represented by the difference Normalized Burn Ratio (dNBR), were parameterized. Although model calibration was difficult due to lack of spatial and temporal measured data, the results show that average post-fire net erosion rates were significantly higher in the wildfire scenarios (5.95 ton ha<sup>-1</sup> yr<sup>-1</sup>) compared to those of a non-wildfire scenario (0.58 ton ha<sup>-1</sup> yr<sup>-1</sup>). Furthermore, erosion values increased with a higher level of burnt severity and multiple fires increased the overall sediment build-up in the catchment, fostering an increase in background sediment yield. Simulated erosion patterns showed great spatial variability with large deposition and erosion rates inside streams. Due to this variability, it was difficult to identify land uses that were most sensitive for post-fire erosion, because some land-uses were located in more erosion-sensitive areas (e.g. streams, gullies) or were more affected by high burnt severity levels than others. Despite these limitations, LAPSUS performed well on addressing spatial sediment processes and has the ability to contribute to pre-fire management strategies. For instance, the percentage soil loss map (i.e. comparison of erosion and soil depth maps) could identify locations at risk.</p>

scholarly journals Bedload transport controls bedrock erosion under sediment-starved conditions

2015 ◽  
Vol 3 (3) ◽  
pp. 291-309 ◽  
Author(s):  
A. R. Beer ◽  
J. M. Turowski
Keyword(s):  
Erosion Rate ◽  
Landscape Evolution ◽  
Bedload Transport ◽  
Minor Importance ◽  
Stream Power ◽  
Catchment Scale ◽  
Data Set ◽  
Erosion Processes ◽  
Bedrock Erosion ◽  
Mountainous Landscape

Abstract. Fluvial bedrock incision constrains the pace of mountainous landscape evolution. Bedrock erosion processes have been described with incision models that are widely applied in river-reach and catchment-scale studies. However, so far no linked field data set at the process scale had been published that permits the assessment of model plausibility and accuracy. Here, we evaluate the predictive power of various incision models using independent data on hydraulics, bedload transport and erosion recorded on an artificial bedrock slab installed in a steep bedrock stream section for a single bedload transport event. The influence of transported bedload on the erosion rate (the "tools effect") is shown to be dominant, while other sediment effects are of minor importance. Hence, a simple temporally distributed incision model, in which erosion rate is proportional to bedload transport rate, is proposed for transient local studies under detachment-limited conditions. This model can be site-calibrated with temporally lumped bedload and erosion data and its applicability can be assessed by visual inspection of the study site. For the event at hand, basic discharge-based models, such as derivatives of the stream power model family, are adequate to reproduce the overall trend of the observed erosion rate. This may be relevant for long-term studies of landscape evolution without specific interest in transient local behavior. However, it remains to be seen whether the same model calibration can reliably predict erosion in future events.

scholarly journals Impact of Land Use/Cover Changes on Soil Erosion in Western Kenya

2020 ◽  
Vol 12 (22) ◽  
pp. 9740
Author(s):  
Benjamin Kipkemboi Kogo ◽  
Lalit Kumar ◽  
Richard Koech
Keyword(s):  
Land Use ◽  
Soil Erosion ◽  
Soil Loss ◽  
Crop Production ◽  
Western Kenya ◽  
Useful Knowledge ◽  
Erosion Rates ◽  
Erosion Processes ◽  
Multi Temporal ◽  
The Impact

This study examined the impact of land use/cover changes on soil erosion in western Kenya in the years 1995 and 2017. The study used the GIS-based Revised Universal Soil Loss Equation (RUSLE) modelling approach and remote sensing assessment. The results showed that the average soil loss through sheet, rill and inter-rill soil erosion processes was 0.3 t/ha/y and 0.5 t/ha/y, in the years 1995 and 2017, respectively. Of the total soil loss, farms contributed more than 50%, both in 1995 and 2017 followed by grass/shrub (7.9% in 1995 and 11.9% in 2017), forest (16% in 1995 and 11.4% in 2017), and the least in built-up areas. The highest soil erosion rates were observed in farms cleared from forests (0.84 tons/ha) followed by those converted from grass/shrub areas (0.52 tons/ha). The rate of soil erosion was observed to increase with slope due to high velocity and erosivity of the runoff. Areas with high erodibility in the region are found primarily in slopes of more than 30 degrees, especially in Mt. Elgon, Chereng’anyi hills and Elgeyo escarpments. This study forms the first multi-temporal assessment to explore the extent of soil erosion and seeks to provide a useful knowledge base to support decision-makers in developing strategies to mitigate soil erosion for sustainable crop production.

Estimation of erosion model erodibility parameters from media properties

Soil Research ◽  
2000 ◽  
Vol 38 (2) ◽  
pp. 265 ◽  
Author(s):  
G. J. Sheridan ◽  
H. B. So ◽  
R. J. Loch ◽  
C. M. Walker
Keyword(s):  
Overland Flow ◽  
Prediction Models ◽  
Field Capacity ◽  
Stepwise Multiple Regression ◽  
Organic Carbon Content ◽  
Regression Equations ◽  
Sediment Delivery ◽  
Data Set ◽  
Erosion Rates ◽  
Erosion Processes

The aim of this research was to enable erodibility values for hillslope-scale erosion prediction models to be determined from easily measured media properties. Simulated rainfall and overland flow experiments were carried out on 34 soils and overburdens from 15 Queensland open-cut coal mines at The University of Queensland Erosion Processes Laboratory. Properties of the 34 media determined included aggregate stability, Atterberg limits, bulk density, cation exchange capacity, dispersion ratios, electrical conductivity, exchangeable sodium percentage, organic carbon content, pH, texture, and water content at field capacity and wilting point. Correlation and stepwise multiple regression procedures were used to determine those media properties that could best be used to predict rill and interill erodibility. Correlations between media properties and sediment delivery at each of 5, 10, 15, 20, and 30% slope revealed that different media properties were correlated with erosion rates at different slopes. A media property could show a strong correlation with erodibility at 30% slope, and a low correlation at 5% slope. Splitting the data set into soils only, and overburdens only, showed that properties that were positively correlated with erosion rates for one group could be negatively correlated for the other group. Therefore, in this study, erodibility could not be explicitly linked to one set of media properties for all medium types and erosive conditions. It was concluded that a single regression equation could not be used to predict erodibility under all conditions. Instead, 4 equations were developed to predict rill and interill erodibility, for soils and overburdens separately. The need for separate regression equations was attributed to the presence of different erosive sub-processes for specific combinations of medium type and slope gradient.

scholarly journals Evaluating post-glacial bedrock erosion and surface exposure duration by coupling in situ optically stimulated luminescence and <sup>10</sup>Be dating

2019 ◽  
Vol 7 (3) ◽  
pp. 633-662 ◽  
Author(s):  
Benjamin Lehmann ◽  
Frédéric Herman ◽  
Pierre G. Valla ◽  
Georgina E. King ◽  
Rabiul H. Biswas
Keyword(s):  
Exposure Duration ◽  
Numerical Approach ◽  
Optically Stimulated Luminescence ◽  
Surface Erosion ◽  
Erosion Rates ◽  
Exposure Dating ◽  
Quaternary Glaciation ◽  
Bedrock Erosion ◽  
Bedrock Surface ◽  
The Impact

Abstract. Assessing the impact of Quaternary glaciation at the Earth's surface implies an understanding of the long-term evolution of alpine landscapes. In particular, it requires simultaneous quantification of the impact of climate variability on past glacier fluctuations and on bedrock erosion. Here we present a new approach for evaluating post-glacial bedrock surface erosion in mountainous environments by combining terrestrial cosmogenic nuclide 10Be (TCN) and optically stimulated luminescence (OSL) surface exposure dating. Using a numerical approach, we show how it is possible to simultaneously invert bedrock OSL signals and 10Be concentrations into quantitative estimates of post-glacial exposure duration and bedrock surface erosion. By exploiting the fact that OSL and TCN data are integrated over different timescales, this approach can be used to estimate how bedrock erosion rates vary spatially and temporally since glacier retreat in an alpine environment.

scholarly journals Moderate topsoil erosion rates constrain the magnitude of the erosion-induced carbon sink and agricultural productivity losses on the Chinese Loess Plateau

2016 ◽  
Vol 13 (16) ◽  
pp. 4735-4750 ◽  
Author(s):  
Jianlin Zhao ◽  
Kristof Van Oost ◽  
Longqian Chen ◽  
Gerard Govers
Keyword(s):  
Loess Plateau ◽  
Carbon Sink ◽  
Agricultural Productivity ◽  
Chinese Loess Plateau ◽  
Maximum Magnitude ◽  
Chinese Loess ◽  
Erosion Rates ◽  
Erosion Processes ◽  
Recent Estimate ◽  
The Impact

Abstract. Despite a multitude of studies, overall erosion rates as well as the contribution of different erosion processes on Chinese Loess Plateau (CLP) remain uncertain, which hampers a correct assessment of the impact of soil erosion on carbon and nutrient cycling as well as on crop productivity. In this paper we used a novel approach, based on field evidence, to reassess erosion rates on the CLP before and after conservation measures were implemented (1950 vs. 2005). We found that current average topsoil erosion rates are 3 to 9 times lower than earlier estimates suggested. Under 2005 conditions, more sediment was produced by non-topsoil erosion (gully erosion (0.23 ± 0.28 Gt yr−1) and landsliding (0.28 ± 0.23 Gt yr−1) combined) than by topsoil erosion (ca. 0.30 ± 0.08 Gt yr−1). Overall, these erosion processes mobilized ca. 4.77 ± 1.96 Tg yr−1 of soil organic carbon (SOC): the latter number sets the maximum magnitude of the erosion-induced carbon sink, which is ca. 4 times lower than one other recent estimate suggests. The programs implemented from the 1950s onwards reduced topsoil erosion from 0.51 ± 0.13 to 0.30 ± 0.08 Gt yr−1 while SOC mobilization was reduced from 7.63 ± 3.52 to 4.77 ± 1.96 Tg C yr−1. Conservation efforts and reservoir construction have disrupted the equilibrium that previously existed between sediment and SOC mobilization on the one hand and sediment and SOC export to the Bohai sea on the other hand: nowadays, most eroded sediments and carbon are stored on land. Despite the fact that average topsoil losses on the CLP are still relatively high, a major increase in agricultural productivity has occurred since 1980. Fertilizer application rates nowadays more than compensate for the nutrient losses by (topsoil) erosion: this was likely not the case before the dramatic rise of fertilizer use that started around 1980. Hence, erosion is currently not a direct threat to agricultural productivity on the CLP but the long-term effects of erosion on soil quality remain important.

scholarly journals Splash Erosion on Terraces, Does It Make a Difference If the Terracing Is Done before or after a Fire?

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 180
Author(s):  
María Fernández-Raga ◽  
Martinho A. S. Martins ◽  
Elena Marcos Porras ◽  
Roberto Fraile ◽  
Jan Jacob Keizer
Keyword(s):  
Meteorological Data ◽  
Soil Aggregates ◽  
Type Model ◽  
Subsurface Hydrology ◽  
Splash Erosion ◽  
Erosion Rates ◽  
Erosion Processes ◽  
High Degree ◽  
The Impact ◽  
Fire Conditions

Terraces are a common Mediterranean feature influencing soils, slopes and subsurface hydrology; however, little is known about their impact on erosion processes, especially in humid regions. The purpose of this study was to assess how terracing after a fire affected erosion processes such as splash erosion. For 8 months, the study monitored splash erosion in three terraced plots, one plot under pre-fire conditions and the other two under post-fire conditions. Assessment of the impact of the terracing treatment in such plots was carried out by the installation of two different splash erosion quantitative systems: cups and funnels. An analysis of the splash data obtained in 17 rainfall events and meteorological data collected during each one of those periods was then performed. A significant positive correlation between the amount of rainfall and the splash erosion was observed. The two splash sampling systems show a high degree of concordance; however, the funnel-type model seems to be the most appropriate when it comes to preventing loss of splashed soil samples. The post-fire treatment with terracing leads to a smaller stability of surface soil aggregates, causing higher splash erosion rates. Sampling using the funnel system collects three times the amount of splashed soil than that collected by the cup system, although both systems correlate appropriately with the meteorological parameters.

Quantifying the erosion of the world’s largest impact crater using cosmogenic nuclides: the Vredefort Dome, South Africa.

2021 ◽  
Author(s):  
Rivoningo Khosa ◽  
Stephen Tooth ◽  
Jan Kramers ◽  
Vela Mbele ◽  
Lee Corbett ◽  
...  
Keyword(s):  
Impact Crater ◽  
Single Channel ◽  
Cosmogenic Nuclides ◽  
River Channel ◽  
Erosion Rates ◽  
Rock Types ◽  
Vaal River ◽  
Bedrock Erosion ◽  
The World ◽  
The Impact

&lt;p&gt;The world&amp;#8217;s largest meteorite impact crater, the Vredefort Dome, has been the subject of extensive studies relating to its age, geology and geomorphology. However, there are no studies pertaining to the rate at which the rocks in the crater remnant are eroding, which can provide insight into the development of the landform over time. This study used the cosmogenic nuclides &lt;sup&gt;10&lt;/sup&gt;Be and &lt;sup&gt;26&lt;/sup&gt;Al, extracted from purified quartz samples, to investigate erosion rates along the Vaal River as it traverses the impact crater. The Vaal River flows in mixed bedrock-alluvial terrain through the dome, crossing two different bedrock lithologies. The river is multi-channelled (anabranching) atop the granitoids exposed in the core of the dome, then downstream flows as a single channel through a narrow canyon cut into the quartzites that form the rim of the dome. We collected 14 samples from the two rock types to assess lithologic controls on erosion rate and determine landscape erosion history. Results from the analysis of both isotopes were in close agreement; here, we report outcrop erosion rates based on the &lt;sup&gt;10&lt;/sup&gt;Be. The average &lt;sup&gt;10&lt;/sup&gt;Be-determined erosion rates (&amp;#177; 1 SD)&lt;strong&gt; &lt;/strong&gt;along the active river channel for the quartzite (n = 4) and granitoid (n = 6) regions are 1.90 &amp;#177; 0.12 and 2.19 &amp;#177; 0.14 m/Ma respectively. &amp;#160;Additional samples from older, now elevated (&gt;5 m) strath terraces developed atop quartzite (n = 4) indicate slightly lower average apparent erosion rates of 1.65 (&amp;#177; 0.09) m/Ma. &amp;#160;The data demonstrate that the erosion rates along the active river channel are similar between the two lithologies despite differences in rock hardness. &amp;#160;The resistant, slowing eroding quartzites serve as the local base level for the river upstream, promoting the development of anabranching, which disperses bedrock erosion over a wider area of the crater. We infer that both bedrock hardness and channel characteristics are important controls on erosion rates along the river.&amp;#160; Collectively, the dataset further illustrates the low bedrock erosion rates that prevail across large areas of the southern African interior.&lt;/p&gt;

scholarly journals The impact of road and railway embankments on runoff and soil erosion in eastern Spain

2015 ◽  
Vol 12 (12) ◽  
pp. 12947-12985 ◽  
Author(s):  
P. Pereira ◽  
A. Gimeìnez-Morera ◽  
A. Novara ◽  
S. Keesstra ◽  
A. Jordán ◽  
...  
Keyword(s):  
Land Use ◽  
Soil Erosion ◽  
Overland Flow ◽  
Erosion Rates ◽  
Infiltration Rates ◽  
Erosion Processes ◽  
Land Use Types ◽  
Soil Erosion Rates ◽  
On The Road ◽  
The Impact

Abstract. Road and railway infrastructure increased in the Mediterranean region during the last three decades. This included the building of embankments, which are assumed to be a~large source of sediments and runoff. However, little is known about soil erosion rates, the factors that control them, and the processes that contribute to detachment, transport and deposition of sediments from road and railway embankments. The objective of this study was therefore to assess the impacts of road and railway embankments as a source of sediment and water, and compare them to other land use types (citrus plantations and shrublands) representative of the Cànyoles watershed to evaluate the importance of road embankments as a~source of water and sediment under high magnitude low frequency rainfall events. Sixty rainfall experiments (1 m2 plots; 60 min duration; 78 mm h−1 rainfall intensity) were carried out on these land use types: 20 on two railway embankments (10 + 10), 20 on two road embankments (10 + 10), and 10 on citrus and 10 on shrubland. Road and railway embankments were characterized by bare soils with low organic matter and high bulk density. Erosion processes were more active in road, railway and citrus plots, and null in the shrublands. The non-sustainable soil erosion rates of 3 Mg ha−1 y−1 measured on the road embankments were due to the efficient runoff connectivity plus low infiltration rates within the plot as the runoff took less than one minute to reach the runoff outlet. Road and railway embankments are both an active source of sediments and runoff, and soil erosion control strategies must be applied. The citrus plantations also act as a~source of water and sediments (1.5 Mg ha−1 y−1), while shrublands are sediment sinks, as no overland flow was observed due to the high infiltration rates.

scholarly journals An optimal data set approach for erosion-impacted soil quality assessments---A case study of an agricultural catchment in the Mollisol region of Northeast China

2021 ◽  
Author(s):  
Jiaqiong Zhang ◽  
Fenli Zheng ◽  
Zhi Li ◽  
Zhizhen Feng
Keyword(s):  
Soil Erosion ◽  
Soil Quality ◽  
Selection Procedure ◽  
Data Set ◽  
Erosion And Deposition ◽  
Erosion Rates ◽  
Novel Approach ◽  
Cesium 137 ◽  
Quality Assessments ◽  
The Impact

Given that soil erosion is a primary cause of land degradation globally, it has been receiving increasing attention in food production regions, such as the Mollisol region in northeastern China. This study assessed soil quality under soil erosion degradation using a novel optimal data set (ODS) approach and a comparative minimum data set (MDS) approach based on soil quality indices (SQIs) within an agriculture watershed in Bin County, Heilongjiang Province, China. SQIs selection was contingent on multiple soil factors. Soil erosion rates was determined using cesium-137 technique. Relationships between soil quality and erosion or deposition rates were also analyzed. Results showed that erosion primarily drove soil redistribution, and soil quality grades were generally extremely low (approx. 80% of sampling sites), based on results from both the MDS and ODS approaches. However, soil quality varied significantly between erosion and deposition sites, it increased from upstream to midstream to downstream areas. Moreover, changes in SQIs and erosion rates exhibited spatially opposite trends, indicative of the impact that soil erosion has on soil quality, which was also confirmed by comparing representative soil properties at soil erosion and deposition sites. The good correlation between the MDS and ODS approaches indicated the feasibility of the ODS approach in estimating soil quality. Finally, the ODS approach is a cause-related method applying a relatively strict indicator selection procedure, which, compared to the MDS approach, could theoretically obtain more reliable results. Further studies are nevertheless necessary to assess the feasibility of this novel approach in other cases.

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