scholarly journals Emergent simplicity despite local complexity in eroding fluvial landscapes

2021 ◽  
Author(s):  
Gareth Roberts
Keyword(s):  
Field Observations ◽  
Local Conditions ◽  
Erosion Rates ◽  
Local Complexity ◽  
Small Scales ◽  
River Profiles ◽  
Topographic Evolution

Much understanding of continental topographic evolution is rooted in measuring and predicting rates at which rivers erode. Flume tank and field observations indicate that stochasticity and local conditions play important roles in determining rates at small scales (e.g. < 10 km, thousands of years). Obversely, preserved river profiles and common shapes of rivers atop uplifting topography indicate that erosion rates are predictable at larger scales. These observations indicate that the response of rivers to forcing can be scale dependent. Here I demonstrate that erosional thresholds can provide an explanation for why profile evolution can be very complicated and unique at small scales yet simple and predictable at large scales.

scholarly journals Emergent simplicity despite local complexity in eroding fluvial landscapes

Geology ◽  
2021 ◽  
Author(s):  
Gareth G. Roberts
Keyword(s):  
Current Understanding ◽  
Field Observations ◽  
Local Conditions ◽  
Erosion Rates ◽  
Local Complexity ◽  
Small Scales ◽  
River Profiles ◽  
Topographic Evolution

Much of our current understanding of continental topographic evolution is rooted in measuring and predicting the rates at which rivers erode the landscape. Flume tank and field observations indicate that stochasticity and local conditions play important roles in determining rates at small scales (e.g., &lt;10 km, thousands of years). Obversely, preserved river profiles and common shapes of rivers atop uplifting topography indicate that erosion rates are predictable at larger scales. These observations indicate that the response of rivers to forcing can be scale dependent. I demonstrate that erosional thresholds can provide an explanation for why profile evolution can be very complicated and unique at small scales yet simple and predictable at large scales.

scholarly journals Seasonal variability of hydrodynamics in the Vistula Estuary in 1994

2007 ◽  
Vol 36 (4) ◽  
Author(s):  
Małgorzata Robakiewicz
Keyword(s):  
Wind Direction ◽  
Water Body ◽  
Seasonal Variability ◽  
River Mouth ◽  
Meteorological Conditions ◽  
Field Observations ◽  
Mixing Processes ◽  
Local Conditions ◽  
Open Sea ◽  
Region Model

Seasonal variability of hydrodynamics in the Vistula Estuary in 1994The Vistula Estuary is a coastal water body boasting free connection with the open sea, where mixing processes of marine and fluvial waters are maintained by local conditions. Based on results from a hydrodynamic model, applied to represent conditions in the year 1994, and using salinity as a tracer, it was found that fluvial water has a tendency to spread westward from the river mouth. This is in contradiction with the dominant wind direction in the region. Model results confirmed field observations of specific hydrological and meteorological conditions required to transport fluvial water northward, towards the Hel Peninsula.

Evaluating the effect of variable lithologies on rates of knickpoint migration in the Wutach catchment, southern Germany

2020 ◽  
Author(s):  
Andreas Ludwig ◽  
Wolfgang Schwanghart ◽  
Florian Kober ◽  
Angela Landgraf
Keyword(s):  
Transient Response ◽  
Stream Power ◽  
Main Trunk ◽  
Southern Germany ◽  
Level Change ◽  
Base Level ◽  
Bulk Parameter ◽  
River Profiles ◽  
Topographic Evolution ◽  
Headward Erosion

&lt;p&gt;The topographic evolution of landscapes strongly depends on the resistance of bedrock to erosion. Detachment-limited fluvial landscapes are commonly analyzed and modelled with the stream power incision model (SPIM) which parametrizes erosional efficiency by the bulk parameter K whose value is largely determined by bedrock erodibility. Inversion of the SPIM using longitudinal river profiles enables resolving values of K if histories of rock-uplift or base level change are known. Here, we present an approach to estimate K-values for the Wutach catchment, southern Germany. The catchment is a prominent example of river piracy that occurred ~18 ka ago as response to headward erosion of a tributary to the Rhine. Base level fall of up to 170 m triggered a wave of upstream migrating knickpoints that represent markers for the transient response of the landscape. Knickpoint migration along the main trunk stream and its tributaries passed different lithological settings, which allows us to estimate K for crystalline and sedimentary bedrock units of variable erodibility.&lt;/p&gt;

scholarly journals MORPHODYNAMIC OF BEACH SCARPS ON A MACROTIDAL COAST DURING EXCEPTIONAL WATER LEVEL EVENTS (NORMANDY, FRANCE)

2012 ◽  
Vol 1 (33) ◽  
pp. 11
Author(s):  
Yoann Bonte ◽  
Franck Levoy
Keyword(s):  
Water Level ◽  
Conceptual Models ◽  
High Tide ◽  
Weather Conditions ◽  
Qualitative Description ◽  
Field Observations ◽  
Fair Weather ◽  
Physical Processes ◽  
Data Set ◽  
Local Conditions

Although there are numerous studies on the morphology and physical processes affecting the dune's scarp and many conceptual models describing beach scarps on microtidal and mesotidal environments (Sunamura, 1985a ; Short,1999), really quantitative informations about the beach scarp formation is lacking, especially along tidal environments where the tide controls the level of wave attack. However, Sherman and Nordstrom(1985) give a qualitative description of beach scarp formations and evolution based on field observations but without data set. The coast of Calvados (Normandy, France) is a fine example of a macrotidal coast, where beach scarps have been often observed. Along macrotidal beaches, the formation of a berm is classically observed during fair weather conditions which contribute to stabilize the coastline. During stormy conditions, the low atmosphere pressure, short waves and onshore winds cause an increase of the water level, which during spring tides, increases the high tide water level time action. Consequently, the natural berm protecting the dune foot, or sometimes a seawall foot, is threatened by erosion and often destroyed. The goal of this study is to quantify the beach scarp destruction (foot and crest scarp retreat speed, eroded volume...) in relation with the hydraulic and morphologic local conditions.

scholarly journals A segmentation approach for the reproducible extraction and quantification of knickpoints from river long profiles

2018 ◽  
Author(s):  
Boris Gailleton ◽  
Simon M. Mudd ◽  
Fiona J. Clubb ◽  
Daniel Peifer ◽  
Martin D. Hurst
Keyword(s):  
Landscape Evolution ◽  
Channel Length ◽  
Negative Slope ◽  
Erosion Rates ◽  
Quadrilátero Ferrífero ◽  
Extraction Algorithm ◽  
Tectonically Active ◽  
Segmentation Approach ◽  
Reproducible Method ◽  
River Profiles

Abstract. Changes in the steepness of river profiles or abrupt vertical steps (i.e. waterfalls) are thought to be indicative of changes in erosion rates, lithology, or other factors that affect landscape evolution. These changes are referred to as knickpoints or knickzones and are pervasive in bedrock river systems. Such features are thought to reveal information about landscape evolution and patterns of erosion, and therefore their locations are often reported in the geomorphic literature. It is imperative that studies reporting knickpoints and knickzones use a reproducible method of quantifying their locations, as their number and spatial distribution play an important role in interpreting tectonically active landscapes. In this contribution we introduce a reproducible knickpoint and knickzone extraction algorithm that uses river profiles transformed by integrating drainage area along channel length (the so-called integral or χ method). The profile is then statistically segmented and the differing slopes and step changes in elevations of these segments are used to identify knickpoints and knickzones, and their relative magnitudes. The output locations of identified knickpoints and knickzones compare favourably with human mapping: we test the method on Santa Cruz Island, CA, using previously reported knickzones and also test the method against a new dataset from the Quadrilátero Ferrífero in Brazil. The algorithm allows extraction of varying knickpoint morphologies, including stepped, positive slope-breaks (concave upward) and negative slope-break knickpoints. We identify parameters that most affect the resulting knickpoint and knickzone locations, and provide guidance for both usage and outputs of the method to produce reproducible knickpoint datasets.

scholarly journals A segmentation approach for the reproducible extraction and quantification of knickpoints from river long profiles

2019 ◽  
Vol 7 (1) ◽  
pp. 211-230 ◽  
Author(s):  
Boris Gailleton ◽  
Simon M. Mudd ◽  
Fiona J. Clubb ◽  
Daniel Peifer ◽  
Martin D. Hurst
Keyword(s):  
Landscape Evolution ◽  
Channel Length ◽  
Negative Slope ◽  
Erosion Rates ◽  
Quadrilátero Ferrífero ◽  
Extraction Algorithm ◽  
Tectonically Active ◽  
Segmentation Approach ◽  
Reproducible Method ◽  
River Profiles

Abstract. Changes in the steepness of river profiles or abrupt vertical steps (i.e. waterfalls) are thought to be indicative of changes in erosion rates, lithology or other factors that affect landscape evolution. These changes are referred to as knickpoints or knickzones and are pervasive in bedrock river systems. Such features are thought to reveal information about landscape evolution and patterns of erosion, and therefore their locations are often reported in the geomorphic literature. It is imperative that studies reporting knickpoints and knickzones use a reproducible method of quantifying their locations, as their number and spatial distribution play an important role in interpreting tectonically active landscapes. In this contribution we introduce a reproducible knickpoint and knickzone extraction algorithm that uses river profiles transformed by integrating drainage area along channel length (the so-called integral or χ method). The profile is then statistically segmented and the differing slopes and step changes in the elevations of these segments are used to identify knickpoints, knickzones and their relative magnitudes. The output locations of identified knickpoints and knickzones compare favourably with human mapping: we test the method on Santa Cruz Island, CA, using previously reported knickzones and also test the method against a new dataset from the Quadrilátero Ferrífero in Brazil. The algorithm allows for the extraction of varying knickpoint morphologies, including stepped, positive slope-break (concave upward) and negative slope-break knickpoints. We identify parameters that most affect the resulting knickpoint and knickzone locations and provide guidance for both usage and outputs of the method to produce reproducible knickpoint datasets.

Olivine enrichment in dehydration veins in serpentinites by reactive fluid flow

2021 ◽  
Author(s):  
Konstantin Huber ◽  
Johannes C. Vrijmoed ◽  
Timm John
Keyword(s):  
Fluid Flow ◽  
Subduction Zones ◽  
Water Cycle ◽  
Oceanic Lithosphere ◽  
High Abundance ◽  
Field Observations ◽  
Reactive Fluid ◽  
Ligurian Alps ◽  
Small Scales ◽  
Reactive Fluid Flow

&lt;p&gt;Serpentinite dehydration in subduction zones plays an important role in Earth&amp;#8217;s deep water cycle. In order to keep this water cycle in balance, an efficient rock dehydration mechanism at depth is needed to keep pace with loss of ocean water due to subduction of hydrated oceanic lithosphere. Field observations in non-deformed meta-serpentinites in Erro Tobbio, Ligurian Alps, show that serpentinite dehydration at depth occurs by a channelized vein network rather than pervasive flow. The mineral assemblage in the veins is characterized by a high abundance of metamorphic olivine. Pl&amp;#252;mper et al. (2017) showed that on small scales (&amp;#956;m-mm) the formation of these veins is controlled by intrinsic chemical heterogeneities in the rock. Field observations suggest that on larger scales the fluid escape is governed by mechanical processes such as hydraulic fracturing. On small scales, where dehydration is chemically controlled, reactive fluid flow is an important process because changes in the fluid chemistry may trigger or hinder further dehydration reactions in the rock. Because of its high solubility and high abundance as a rock forming component, Si might be a key metasomatic agent for first-order effects on the dehydration process.&lt;/p&gt;&lt;p&gt;Following the approach of Beinlich et al. (2020) we extended the model of Pl&amp;#252;mper et al. (2017) to a reactive fluid flow model for serpentinite dehydration that accounts for the Si content of the fluid. As input for our model we use mineral chemical data of non-dehydrated serpentinites from the Mirdita ophiolite in Albania that are representative for serpentinized oceanic lithosphere that enters a subduction zone, hence has not experienced any subduction-related metamorphic processes. The results of our model suggest that the high abundance of metamorphic olivine observed in the Erro Tobbio meta-serpentinites hence the purification towards a olivine-dominated assemblage is the result of interaction with an external fluid in the veins after they have been formed from the intrinsic chemical heterogeneities.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Beinlich, A. et al. (2020). &amp;#8220;Instantaneous rock transformations in the deep crust driven by&lt;br&gt;reactive fluid flow&amp;#8221;. In: Nature Geoscience 13.4, pp. 307&amp;#8211;311. doi: 10.1038/s41561-&lt;br&gt;020-0554-9.&lt;/li&gt; &lt;li&gt;Pl&amp;#252;mper, O. et al. (2017). &amp;#8220;Fluid escape from subduction zones controlled by channel-&lt;br&gt;forming reactive porosity&amp;#8221;. In: Nature Geoscience 10.2, pp. 150&amp;#8211;156. doi: 10.1038/&lt;br&gt;NGEO2865.&lt;/li&gt; &lt;/ul&gt;

scholarly journals Biological Productivity of the Great Lakes of Russia: Comparison of Simulating Results and Field Observations

2017 ◽  
Author(s):  
Keyword(s):  
Great Lakes ◽  
Mass Balance ◽  
Trophic Status ◽  
Balance Model ◽  
Expert Assessment ◽  
Field Observations ◽  
Mass Balance Model ◽  
Biological Productivity ◽  
Local Conditions ◽  
Fish Catch

Results of analysis of the mass-balance model simulating biotic energy flows in the great lakes of Russia –Ladoga, Onego and Baikal- ecosystems have been presented. Season-average biomass and annual production of prime producers, reducers and consumers including fish have been forecasted. Permissible fish catch has been assessed. The model data were compared with the field observations results. Importance of the great lakes of Russia researches with the use of the mass-balance model is stipulated by their size and value as the biggest and Europe, besides, Lake Baikal is the greatest water body of the world in terms of the fresh water stock. Determination of these lakes’ trophic status is of primary importance for water quality assessment and for prediction their total biological productivity, fish productivity and permissible fish catch. This is possible only provided application of the balance-energy approach based on the knowledge of regularities of the organic matter and energy transfer through the ecosystem trophic units. A forecast of the lakes biological productivity was composed on the basis of quantitative links between key biotic and abiotic components of an aquatic ecosystem summed up in the form of the massbalance model. Results of the model test by the empiric data have shown that it possesses sufficient prediction reliability and is applicable for development of the lacustrine ecosystems’ biotic balances. The model can serve as a good tool for reconstruction of the lacking data and expert assessment of the ecosystems’ trophic status provided the specific local conditions are taken into account. Moreover, it can be used for cross-checking of empiric and the model predicted data reliability.

scholarly journals MODELLING EROSION AND LANDSLIDES INDUCED BY FARMING ACTIVITIES AT HILLY AREAS, CAMERON HIGHLANDS, MALAYSIA

2019 ◽  
Vol 81 (6) ◽  
Author(s):  
A. F. Abdullah ◽  
Aimrun W. ◽  
N. M. Nasidi ◽  
K. Hazari S. A. F. ◽  
L Mohd. Sidek ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Historical Data ◽  
Control Measures ◽  
Field Observations ◽  
Agricultural Activities ◽  
Geospatial Techniques ◽  
Erosion Rates ◽  
Landslide Event ◽  
Cameron Highlands ◽  
Bivariate Statistical Analysis

This work was conducted at hilly farms of Cameron Highlands to model the incidences of soil erosion and landslides using historical data and field observations. IfSAR data with spatial resolution of 5 m was used which enable clear observation and delineation of the geographic features within the study area. Field visits were conducted to various places where landslides occurred on agricultural farms in order to validate the model. Also, the rate of soil erosions was evaluated using geospatial techniques. The potential landslide event and its probability of occurrence were combined using bivariate statistical analysis. The results revealed that most of the landslides incidents were occurred at areas with intensive agricultural activities with no proper erosion control measures. It was gathered that more than 75% of landslides occurred in agricultural activities areas are under sheltered farms. The annual soil erosion rates in both Telom and Bertom Catchments ware 38 ton /ha/year and 73.9 ton /ha/year respectively. It was revealed that, there is high risk of erosion-induced landslides in agricultural farms. However, the erosion induced landslide map shows that most the landslide occurred close to the rivers. This indicated that both agricultural operations and proximity to rivers are influencing factors for the incidences. 

scholarly journals Alpine Rockwall Erosion Patterns Follow Elevation-Dependent Climate Trajectories

2021 ◽  
Author(s):  
Daniel Draebing ◽  
Till Mayer ◽  
Benjamin Jacobs ◽  
Samuel McColl
Keyword(s):  
Climate Change ◽  
Climate Warming ◽  
Landscape Scale ◽  
Tectonic Uplift ◽  
Future Climate ◽  
European Alps ◽  
Field Observations ◽  
Erosion Rates ◽  
Crustal Strength ◽  
The Alps

Abstract Mountainous topography reflects an interplay between tectonic uplift, crustal strength, and climate-conditioned erosion cycles. During glaciations, glacial erosion increases bedrock relief, whereas during interglacials relief is lowered by rockwall erosion. In the first landscape-scale, multi-process investigation of postglacial rockwall erosion patterns, we show that paraglacial, frost cracking and permafrost processes jointly drive rockwall erosion. Field observations and modelling experiments demonstrate that all three processes are strongly conditioned by elevation. Our findings provide a multi-process explanation for the increase of rockwall erosion rates with elevation across the European Alps. As alpine basins warm during deglaciation, changing intensities and elevation-dependent interactions between periglacial and paraglacial processes result in elevational shifts in rockwall erosion patterns. Future climate warming will shift the intensity and elevation distribution of these processes, resulting in overall lower erosion rates across the Alps, but with more intensified erosion at the highest topography most sensitive to climate change.

Sign in / Sign up

Export Citation Format

Share Document