Search

A quantitative analysis of the shoreline migration pattern at various timescales is important to understand the coastal ecosystem and interaction behaviour between sea and land. The sea-level rise due to polar ice and glacier melting has directly affected the coastal environment. The present study attempts to analyze the potential migration characteristics of Jambudwip Island of the Sundarban biosphere in the Bay of Bengal. GIS, Remote Sensing and Statistical analyses have been utilized for this observation. Digital Shoreline Analysis System (DSAS) was used to assess the shoreline change over time span. Moreover, Linear Regression Rate (LRR) and End Point Rate (EPR) were used for statistical analysis to measure the rate of change of shoreline during 2011, 2013, 2015, and 2017. NDVI and single-band threshold method (IR band) has been applied on the Landsat-7 and OLI data to identify the shoreline position. The result showed that the Western part of the island was the most erosive zone and Eastern part is the most accretive zone. Overall, the maximum rate of erosion was 49.08 m/yr and accretion 122.4 m/yr. In consequence, shoreline length has also been changed between 2011and 2017, from approximately 11879.91m to 10374.42 m.

Coastal cliff erosion is alongshore-variable and episodic, with retreat rates that depend upon sediment as either tools of abrasion or protective cover. However, the feedbacks between coastal cliff planform morphology, retreat rate, and sediment cover are poorly quantified. This study investigates Sargent Beach, Texas, USA, at the annual to interannual scale to explore (1) the relationship between temporal and spatial variability in cliff retreat rate, roughness, and sinuosity and (2) the response of retreat rate and roughness to changes in sand and shell hash cover of the underlying mud substrate as well as the impact of major storms using field measurements of sediment cover, erosion, and aerial images to measure shore platform morphology and retreat. A storm event in 2009 increased the planform roughness and sinuosity of the coastal cliff at Sargent Beach. Following the storm, aerial-image-derived shorelines with annual resolution show a decrease in average alongshore erosion rates from 12 to 4 m yr−1, coincident with a decrease in shoreline roughness and sinuosity (smoothing). Like the previous storm, a storm event in 2017 increased the planform roughness and sinuosity of the cliff. Over shorter timescales, monthly retreat of the sea cliff occurred only when the platform was sparsely covered with sediment cover on the shore platform, indicating that the tools and cover effects can significantly affect short-term erosion rates. The timescale to return to a smooth shoreline following a storm or roughening event, given a steady-state erosion rate, is approximately 24 years, with the long-term rate suggesting a maximum of ∼107 years until Sargent Beach breaches, compromising the Gulf Intracoastal Waterway (GIWW) under current conditions and assuming no future storms or intervention. The observed retreat rate varies, both spatially and temporally, with cliff face morphology, demonstrating the importance of multi-scale measurements and analysis for interpretation of coastal processes and patterns of cliff retreat.

The glacial landscape of the Alps has fascinated generations of explorers, artists, mountaineers, and scientists with its diversity, including erosional features of all scales from high-mountain cirques to steep glacial valleys and large overdeepened basins. Using previous glacier modelling results and empirical inferences of bedrock erosion under modern glaciers, we compute a distribution of potential glacier erosion in the Alps over the last glacial cycle from 120 000 years ago to the present. Despite large uncertainties pertaining to the climate history of the Alps and unconstrained glacier erosion processes, the resulting modelled patterns of glacier erosion include persistent features. The cumulative imprint of the last glacial cycle shows a very strong localization of erosion potential with local maxima at the mouths of major Alpine valleys and some other upstream sections where glaciers are modelled to have flowed with the highest velocity. The potential erosion rates vary significantly through the glacial cycle but show paradoxically little relation to the total glacier volume. Phases of glacier advance and maximum extension see a localization of rapid potential erosion rates at low elevation, while glacier erosion at higher elevation is modelled to date from phases of less extensive glaciation. The modelled erosion rates peak during deglaciation phases, when frontal retreat results in steeper glacier surface slopes, implying that climatic conditions that result in rapid glacier erosion might be quite transient and specific. Our results depict the Alpine glacier erosion landscape as a time-transgressive patchwork, with different parts of the range corresponding to different glaciation stages and time periods.

In the Arctic, air temperatures are warming and sea ice is declining, resulting in larger waves and a longer open water season, all of which intensify the thaw and erosion of ice-rich coasts. This change in climate has been shown to increase the rate of Arctic coastal erosion, causing problems for industrial, military, and civil infrastructure as well as changes in nearshore biogeochemistry. Numerical models that reproduce historical and project future Arctic erosion rates are necessary to understand how further climate change will affect these problems, and no such model yet exists to simulate the physics of erosion on a pan-Arctic scale. We have coupled a bathystrophic storm surge model to a simplified physical erosion model of a partially frozen cliff and beach. This Arctic erosion model, called ArcticBeach v1.0, is a first step toward a parameterization of Arctic shoreline erosion for larger-scale models, which are not able to resolve the fine spatial scale (up to about 40 m) needed to capture shoreline erosion rates from years to decades. It is forced by wind speeds and directions, wave period and height, sea surface temperature, all of which are masked during times of sea ice cover near the coastline. Model tuning requires observed historical retreat rates (at least one value), as well as rough nearshore bathymetry. These parameters are already available on a pan-Arctic scale. The model is validated at two study sites at Drew Point (DP), Alaska, and Mamontovy Khayata (MK), Siberia, which are respectively located in the Beaufort and Laptev Seas, on different sides of the Arctic Ocean. Simulated cumulative retreat rates for DP and MK respectively (169 and 170 m) over the time periods studied at each site (2007–2016, and 1995–2018) are found to be within the same order of magnitude as observed cumulative retreat rates (172 and 120 m). Given the large differences in geomorphology and weather systems between the two study sites, this study provides a proof-of-concept that ArcticBeach v1.0 can be applied on very different partially frozen coastlines. ArcticBeach v1.0 provides a promising starting point to project the retreat of Arctic shorelines, or to evaluate historical retreat in places that have had few observations. Further, this model can provide estimates of the flux of sediment from land to sea for Arctic nearshore biogeochemical studies, while leaving an opportunity for further development of modelling the physics of a partially frozen shoreline.

Over the past few decades, developments in remote sensing have resulted in an ever-growing availability of topographic information on a global scale. A recent development is TanDEM-X (TerraSAR-X add-on for digital elevation measurements), an interferometric synthetic aperture radar (SAR) mission of the Deutsche Zentrum für Luft- und Raumfahrt, providing near-global coverage and 12 m resolution digital elevation models (DEMs). Moreover, ongoing developments in uncrewed aerial vehicle (UAV) technology have enabled acquisitions of topographic information at a sub-meter resolution. Although UAV products are generally preferred for volume assessments of geomorphic features, their acquisition remains a time-consuming task and is spatially constrained. However, some applications in geomorphology, such as the estimation of regional or national erosion quantities of specific landforms, require data over large areas. TanDEM-X data can be applied at such scales, but this raises the question of how much accuracy is lost because of the lower spatial resolution. Here, we evaluated the performance of the 12 m TanDEM-X DEM to (i) estimate gully volume, (ii) establish an area–volume relationship, and (iii) determine mobilization rates through comparison with a higher-resolution (0.2 m) UAV structure-from-motion (SfM) DEM and a lower resolution (30 m) Copernicus DEM. We did this for six study areas in the Lake Alaotra region (central Madagascar), where lavaka (gullies) are omnipresent and surface area changes over the period 1949–2010s are available for 699 lavaka. Copernicus-derived lavaka volume estimates were systematically too low, indicating that the Copernicus DEM is too coarse to accurately estimate volumes of geomorphic features at the lavaka scale (100–105 m2). Lavaka volumes obtained from TanDEM-X were similar to UAV-SfM volumes for the largest features, whereas the volumes of smaller features were generally underestimated. To deal with this bias we introduce a breakpoint analysis to eliminate volume reconstructions that suffer from processing errors as evidenced by significant fractions of negative volumes. This elimination allowed the establishment of an area–volume relationship for the TanDEM-X data with fitted coefficients within the 95 % confidence interval of the UAV-SfM relationship. Our calibrated area–volume relationship enabled us to obtain large-scale lavaka mobilization rates ranging between 18 ± 3 and 311 ± 82 tha-1yr-1 for the six different study areas, with an average of 108 ± 26 tha-1yr-1 for the full dataset. These results indicate that current lavaka mobilization rates are 2 orders of magnitude higher than long-term erosion rates. With this study we demonstrate that the global TanDEM-X 12 m DEM can be used to accurately estimate volumes of gully-shaped features at the lavaka scale (100–105 m2), where the proposed breakpoint method can be applied without requiring the availability of a higher-resolution DEM. Furthermore, we use this information to make a first assessment of regional lavaka erosion rates in the central highlands of Madagascar.

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.

Made available in DSpace on 2022-04-28T19:47:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Cuestas are relief features whose evolution has traditionally been attributed to erosion processes. They are habitually studied in many regions of the world. In Brazil, however, studies of erosion processes in cuestas are uncommon, despite the presence of this type of relief in several parts of the country. The aim of this study was to identify relevant correlations between local geographical conditions and physical-hydrological properties of the soil, and to identify the prevailing factors in the development of rill erosion, ravines and gullies in cuestas. We analyze various physical properties of the soil, including grain size, resistance to penetration, permeability and infiltration rates. The geographic variable slope was also considered. The data variables were processed using geostatistical techniques (ordinary kriging) and statistics (factor analysis). The results show that data referring to grain size, soil resistance to penetration and infiltration present statistically significant differences and can be used to assess the spatial distribution of erosion landforms. Details of the behavior of clays and the transitions between the clayey and sandy sector also helped to understand the location of erosion landforms. The steep morphology of the cuestas, associated with the presence of lithologies of varying resistance, generates different soil types, even in small catchments. These differentiations contribute to the development of erosion features and generate gullies covering large areas and whose evolution is difficult to explain. Thus, the study of erosion in cuesta lands is necessary and should be expanded in Brazil. The methodology used in this study has the potential to be applied to other catchments, and can thus contribut to the study of erosion processes in cuestas. Programa de Pós-graduação em Geografia São Paulo State University (Unesp), Avenida 24A, n.1515 Departamento de Geografia e Planejamento Ambiental São Paulo State University (Unesp), Avenida 24A, n.1515 Department of Geography Facultat de Geografia i Història Universitat de Barcelona, Montalegre, 6-8, 3 pis Departamento de Ciencias Históricas y Geográficas Universidad de Tarapacá, 18 de Septiembre #2222, Campus Saucache Departament de Geografia Universitat de Barcelona, Montalegre, 6-8, 08001 Programa de Pós-graduação em Geografia São Paulo State University (Unesp), Avenida 24A, n.1515 Departamento de Geografia e Planejamento Ambiental São Paulo State University (Unesp), Avenida 24A, n.1515 CAPES: 2016/25399-1 CAPES: 2018/09746-9

Marine terraces are a cornerstone for the study of paleo sea level and crustal deformation. Commonly, individual erosive marine terraces are attributed to unique sea-level high stands based on the reasoning that marine platforms could only be significantly widened at the beginning of an interglacial. However, this logic implies that wave erosion is insignificant at other times. We postulate that the erosion potential at a given bedrock elevation datum is proportional to the total duration of sea-level occupation at that datum. The total duration of sea-level occupation depends strongly on rock uplift rate. Certain rock uplift rates may promote the generation and preservation of particular terraces while others prevent them. For example, at rock uplift of ~1.2 mm/yr, the Marine Isotope Stage (MIS) 5e (ca. 120 ka) high stand reoccupies the elevation of the MIS 6d–e mid-stand, favoring creation of a wider terrace than at higher or lower rock uplift rates. Thus, misidentification of terraces can occur if each terrace in a sequence is assumed to form uniquely at successive interglacial high stands and to reflect their relative elevations. Developing a graphical proxy for the entire erosion potential of sea-level history allows us to address creation and preservation biases at different rock uplift rates.

Few data are available on how soil erosion rates compare between surfaces of different ages because short-term processes often overprint the longer-term erosion signal. This study investigated the soil dynamics among two end-member sites, a formerly glaciated ('young', maximum glacial extent at 22–30 ka BP) and a non-glaciated ('old') area at the Serra da Estrela (Portugal). To disentangle soil distribution rates over different timeframes, isotopes for long-term (10Be), mid-term (δ13C) and short-term (239+240Pu) periods were applied together with principles of the percolation theory. The formerly glaciated area has soils with a lower degree of weathering and lower carbon content compared to soils of the ‘old‘, non-glaciated area. The selected isotopes and their distribution along the soil profiles revealed temporal differences in soil mixing process. It is hypothesised that the slightly higher elevation and formerly glaciated sites experienced cryoturbation effects over a longer period, while being less active or absent for the last few decades at the older, non-glaciated soils. The average long-term (millennia) soil erosion rates correspond to the expected higher rates at the younger surface and lower rates at the older surface. Once the formerly glaciated area became ice-free, soil erosion rates were high and decreased giving rise to average long-term rates of 101–140 [t km−2 yr−1] for the older surfaces and 176–248 [t km−2 yr−1] for the younger surfaces. In addition, seasonal freeze–thaw of the soils has persisted over a long period and affected the younger soils more intensively than the older soils. The current (last decades) soil redistribution rates, however, are up to one order of magnitude higher than the millennia rates and are controlled by surface angle and vegetation cover and less by soil texture. The more undulated, non-glaciated older surface had the highest short-term (decades) soil erosion rates in the range of 900–1700 [t km−2 yr−1], exhibits degrading conditions and relatively shallow soils. The younger soils, however, showed short-term (last few decades) average soil deposition rates of ∼ 230 [t km−2 yr−1]. Human impact (bush fires, grazing) is the cause for the currently strong soil degradation at the non-glaciated area., Catena, 215

Disentangling the influence of bedrock erodibility from the respective roles of climate, topography and tectonic forcing on catchment denudation is often challenging in mountainous landscapes due to the diversity of geomorphic processes in action and of spatial/temporal scales involved. The Dora Baltea catchment (western Italian Alps) appears the ideal setting for such investigation, since its large drainage system, extending from the Mont Blanc Massif to the Po Plain, cuts across different major litho-tectonic units of the western Alps, whereas this region has experienced homogeneous climatic conditions and glacial history throughout the Quaternary. We acquired new 10Be-derived catchment-wide denudation rates from 18 river-sand samples collected both along the main Dora Baltea river and at the outlet of its main tributaries. The inferred denudation rate results vary between 0.2 and 0.9 mm/yr, consistent with values obtained across the European Alps by previous studies. Spatial variability in denudation rates was statistically compared with topographic, environmental and geologic metrics. 10Be-derived denudation records do not correlate with the distribution of modern precipitation and rock geodetic uplift. We find, rather, that catchment topography, in turn conditioned by bedrock erodibility (litho-tectonic origin) and glacial overprint, has the main influence on denudation rates. We calculated the highest denudation rate for the Mont Blanc Massif, whose granitoid rocks and long-term tectonic uplift support steep slopes and high relief and thus favour intense glacial/periglacial processes and recurring rock fall events. Finally, our results, in agreement with modern sediment budgets, demonstrate that the high sediment input from the Mont Blanc catchment dominates the Dora Baltea sediment flux, explaining the constant low 10Be concentrations measured along the Dora Baltea course even downstream the multiple junctions with tributary catchments.

Coastal urbanisation is a widespread phenomenon throughout the world and is often linked to increased erosion. Small Pacific islands are not spared from this issue, which is of great importance in the context of climate change. The French Polynesian island of Bora Bora was used as a case study to investigate the historical evolution of its coastline classification and position from 1955 to 2019. A time series of very-high-resolution aerial imagery was processed to highlight the changes of the island’s coastline. The overall length of natural shores, including beaches, decreased by 46% from 1955 to 2019 while man-made shores such as seawalls increased by 476%, and as of 2019 represented 61% of the coastline. This evolution alters sedimentary processes: the time series of aerial images highlights increased erosion in the vicinity of seawalls and embankments, leading to the incremental need to construct additional walls. In addition, the gradual removal of natural shoreline types modifies landscapes and may negatively impact marine biodiversity. Through documenting coastal changes on Bora Bora through time, this study highlights the impacts of man-made structures on erosional processes and underscores the need for sustainable coastal management plans in French Polynesia.

Landslide disasters have occurred frequently in the Chinese Loess Plateau (CLP) due to increased agricultural irrigation. To explore the spatiotemporal relationship between landslides and mechanisms at the Heifangtai terrace, the HFT irrigated area was selected as a typical case study to investigate the fundamental mechanism of the irrigation-induced landslide in the CLP. Multi-temporal remote sensing images, topographic maps, and unmanned aerial vehicle (UAV) photogrammetry data were used to investigate the evolution progress of landslides. Moreover, the evolution mechanism was discussed through topographic analysis, field monitoring, and laboratory testing. The results showed that erosion, collapse, and sliding had occurred at different scales and at different locations in the past 50 years. With an average retrogressive speed of 9.6 × 103 m2 per year, the tableland decreased by 4.9 × 105 m2 from 1967 to 2018, accounting for about 4.5% of its total area. Over 20 landslides and collapses were extracted in the Dangchuan section in the past four years. More than 5.48 × 105 m3 of loess slipped with an average volume of 381 m3 per day. The evolutionary process of the irrigation-induced landslide, which features retrogression, lateral extension, and clustering, began with local failure and ended in a series of slidings. The increase of groundwater level was a slow process, which is the reason for the lagged occurrence of the landslide. The influence of rainfall and irrigation on slope stability was greater than that of the periodic change of the groundwater level. The triggering effect of irrigation and rainfall on the landslide had a time lag due to slow loess infiltration, and the time response among irrigation, rainfall, and groundwater level was 4–6 months. Our findings provide guidance, concerning the planning and controlling of landslide disasters, which is of critical value for human and construction safety.

Understanding the interactions between dune systems and beaches is critical to determining the short-term shoreline response and the long-term resilience. In this study, almost 15 years of monthly beach/dune measurements were analysed for three different profiles at Vougot Beach, France to understand and predict shoreline changes from intra- to multi-annual time- scales. Four migration modes: advance/retreat (translation modes) and steepening/flattening (rotation modes) were identified through a centroid analysis. The analysis showed that translation and rotation can occur simultaneously, with long-term trends of beach retreat and profile steepening (lower beach retreating and upper beach advancing), which was interrupted by two energetic wave events causing profile flattening (lower beach advancing and upper beach retreating). These two observations are evidence of how the sediment contribution resulting from the dune erosion events temporarily caused a large advance in the shoreline position. A recent modelling approach that accounts for different time-scales is applied to predict the shoreline changes, showing significant improvements in comparison to a traditional shoreline equilibrium model when time-scales related with the dune erosion and recovery are considered. The results showed that the dune system affects the beach profile evolution both spatially, with different impacts at different elevations along the cross-shore profile, and temporally, by periodically redistributing the sediment in the system. Plain Language Summary Changes in the shoreline position are the result of a delicate balance between hydrodynamic (e.g., waves, currents, water levels) and morphology (e.g., dunes, beachface). Dunes are a natural barrier to storms and much of their ability to stand erosive events is related to their recovery after a storm. At the same time, the beachface often responds to incoming waves by either changing its slope (rotation mode) or by advancing/retreating (translation mode). Using 15 years of profile measurements at Vougot beach, France, we identified the different modes and observed if, when and how they occur. Our analysis shows that the evolution of the beach system was controlled by the sediment exchanges and redistribution between the dune and the intertidal beach. Different elevations of the intertidal beach profile showed distinct behaviour and different time-scales of change. Our work provides evidence that a multi-temporal scale approach is necessary to predict sediment redistribution along the beach profile.

The Yellow River catchment in central China is one of the cradles of Chinese civilization. Since the mid-Holocene, the runoff and erosion in this area, which includes the Chinese Loess Plateau, have been affected by anthropogenic land cover changes (ALCC) and Asian monsoon climatic changes. We applied the reconstructions of Holocene climate (temperature, precipitation, insolation and CO2 concentration) and KK10 land cover change scenarios, to determine the evolution of discharge and sediment flux in the Beiluo River in the Chinese Loess Plateau using the Landlab landscape evolution model combined with a module that considers the impact of vegetation on water balance and soil erodibility. The modeling results show that climate change and ALCC resulted in large fluctuations of both discharge and sediment fluxes since the mid-Holocene. For the evolution of discharge, climate change is the dominant controlling factor, and land-use change has a secondary effect. Comparison of results of modeling scenario's with and without land-use change shows that it contributes less than 5% to changes of runoff during the time period before 1000 BCE. However, the impact of land-use change is significant for sediment load, especially since 5000 BCE. Thus, our results provide evidence for a much earlier start of the human impact on soil erosion and fluvial processes compared to earlier studies. Our modeling also shows that the incorporation of eco-hydrological processes in landscape evolution modeling is important for the accurate simulation of runoff and discharge in response to climate and land-use change, at least in a semi-arid environment.

Aims The stability of hillslopes is an essential ecosystem service, especially in alpine regions with soils prone to erosion. One key variable controlling hillslope stability is soil aggregate stability. We aimed at identifying dominant controls of vegetation parameters on aggregate stability and analysed their importance for soil aggregate stability during landscape development. Methods We quantified the aggregate stability coefficient (ASC) and measured plant cover, diversity, root mass and root length, density (RMD, RLD) along two chronosequences with contrasting bedrocks (siliceous, calcareous) in the Swiss Alps. Results We found that ASC developed slower along the calcareous chronosequence. Furthermore, we observed a significant positive effect of vegetation cover and diversity on ASC that was mediated via root density. These relationships developed in a time-depended manner: At young terrain ages, vegetation parameters had a strong effect on aggregate stability compared to older stages. Moreover, RLD was the most powerful predictor of ASC on young terrain, whereas on older moraines RMD became more important. Conclusions We highlight that root density plays a major role in governing ASC for soils differing in moraine ages. The changing importances of RLD and RMD for ASC development suggest different mechanistic linkages between vegetation and hillsope stability during landscape development.

Observational data of coastal change over much of the Arctic are limited largely due to its immensity, remoteness, harsh environment, and restricted periods of sunlight and ice-free conditions. Barter Island, Alaska, is one of the few locations where an extensive, observational dataset exists, which enables a detailed assessment of the trends and patterns of coastal change over decadal to annual time scales. Coastal bluff and shoreline positions were delineated from maps, aerial photographs, and satellite imagery acquired between 1947 and 2020, and at a nearly annual rate since 2004. Rates and patterns of shoreline and bluff change varied widely over the observational period. Shorelines showed a consistent trend of southerly erosion and westerly extension of the western termini of Barter Island and Bernard Spit, which has accelerated since at least 2000. The 3.2 km long stretch of ocean-exposed coastal permafrost bluffs retreated on average 114 m and at a maximum of 163 m at an average long-term rate (70 year) of 1.6 ± 0.1 m/yr. The long-term retreat rate was punctuated by individual years with retreat rates up to four times higher (6.6 ± 1.9 m/yr; 2012–2013) and both long-term (multidecadal) and short-term (annual to semiannual) rates showed a steady increase in retreat rates through time, with consistently high rates since 2015. A best-fit polynomial trend indicated acceleration in retreat rates that was independent of the large spatial and temporal variations observed on an annual basis. Rates and patterns of bluff retreat were correlated to incident wave energy and air and water temperatures. Wave energy was found to be the dominant driver of bluff retreat, followed by sea surface temperatures and warming air temperatures that are considered proxies for evaluating thermo-erosion and denudation. Normalized anomalies of cumulative wave energy, duration of open water, and air and sea temperature showed at least three distinct phases since 1979: a negative phase prior to 1987, a mixed phase between 1987 and the early to late 2000s, followed by a positive phase extending to 2020. The duration of the open-water season has tripled since 1979, increasing from approximately 40 to 140 days. Acceleration in retreat rates at Barter Island may be related to increases in both thermodenudation, associated with increasing air temperature, and the number of niche-forming and block-collapsing episodes associated with higher air and water temperature, more frequent storms, and longer ice-free conditions in the Beaufort Sea.

The Eastern Rif Mountains are frequently subject to exceptional rainfall events, whose consequences are sometimes disastrous. The impact of these phenomena on environments is more important as the majorities of slopes are bare and subject to strong human influence. The protective natural forests of the slopes are almost destroyed; they currently cover only a few peaks of mountains in the region. They represent 1.84% of the total area of wadi Tleta sub-basin and only 1.32% of the Tarmast wadi sub-basin. However, croplands, occupying respectively 60% and 34% in the two sub-basins, extend even on the steepest slopes. Similarly, the accelerated and uncontrolled human occupation of the urban peripheries, located downstream of the basins, amplifies the vulnerability of these environments to the hydrological hazards, that threaten several sites surrounding the agglomeration of Taza. Thus, the whole region is subject to different degradation processes. Hydric erosion affects the majority of the slopes; it causes excessive sediment production that may exceed 60 t ha -1 year -1 in some sub-basins. Similarly, flood disasters are quite common in the region. The flood of 20/9/2000 is a reference, with a volume estimated at 4 million m 3 (DRH-Sebou 2000). Human and material damage was enormous in the rural centers and in the northern outlying districts of Taza. This contribution aims to present and analyze the combined impacts of the extreme rains and the actions of the human societies on the dynamics of the prerifain environment and its adjoining spaces.

This study investigates the Holocene levee deposits and paleoflooding history of the Lower Meuse in the Netherlands based on archeological investigations and sedimentary analyses (grain size, end-member modelling, magnetic susceptibility and thermogravimetric analyses). The levee on the left bank in the study area near Ooijen contains a continuous sedimentary record in the NW downstream part. The archeological evidence and sedimentary results, including a grain size based flood energy index (LFEI), indicate that the Lower Meuse experienced a quiescent flooding period and low sedimentation rates during the mid-late Mesolithic when the levee was low and human influence was minor. Deposition during the Mesolithic shows a fining-upward trend and a highly-developed soil containing abundant artefacts. During the Neolithic and Bronze Age, the flooding intensity was low but gradually increased to a moderate level probably because of deforestation and increased runoff. Limited Bronze Age findings may reflect decreased human activity because of the increased flooding. Starting from the Iron Age, the Meuse experienced a generally enhanced flooding regime, which is reflected by erosion and coarsened sedimentation in the Iron Age and Roman Period. The high peak discharges during the Iron Age may have re-opened a low-lying paleochannel near to the levee during the intensified floods. This general increasing trend is interrupted by the lower flooding phase in the early Middle Ages (Dark Ages). From the middle to the late Middle Ages, the floods intensified again. The coarsening deposition and higher sedimentation rates since the Iron Age resulted from increased floods and higher sediment supply by deforestation and soil erosion. The findings of this study agree with a recent paleoflood reconstruction for the Lower Meuse by using a floodplain archive, implying that levee sediment records have potential in paleohydrological studies if the completeness of the record and chronological information is guaranteed.

The ecological and biological features of development and the state of gardening stands in urban landscapes of the ancient city are studied. The historical-stylistic genesis of the urban landscapes and the formation of a system of landscape and garden plantations in Lviv are analyzed. Their phytocoenic features, in particular, floristic, spatial, and ecological and population structure, system organization, vitality are investigated and generalized. The influence of spatial structure of city plantations on their vitality and aesthetics is investigated. Urban features of urban degradation changes in parks plantations are studied. The influence of local landscape geosystems and geophysical processes in them on the formation of tocoplimatic characteristics of parks is researched. The ecological and biological differences and peculiarities of the formation of spatial natural phenomena in a certain garden-park composition are elucidated. It has been established that the study of tocoplimatic differences should begin with consideration of solar radiation fluxes, air and soil temperatures, atmospheric precipitation, wind, etc. The influence of physical and geographic factors on the formation of sloping local garden-park composition groups in terms of revealing patterns of formation of their structure and functioning is evaluated. The analysis of territorial ecological and biological differences and special features of the formation of spatial natural phenomena in connection with certain fields and flows of matter and energy has been carried out. The narrow amplitudes of temperature in the geocomplexes of vertices, the middle and the bottom of slopes, the barrier effect on migration and the local transformation of air masses, which affects the specificity of subnatural phytocoenosis, have been revealed. The authors have characterized paying special attention to the top-climatic characteristics for increasing the comfort of development of garden-park composition groups. It is noted that the surface of the hills along with the lace paths laid on the slopes undergoes erosion and requires reduction of recreational load. The negative phenomena are outlined, which, together with the age factor and the lack of proper agrotechnical care, affect the conditions of the location of plantings. The ways of phytomeliorative optimization of the efficiency of gardens and parks of the complex green zone of the city are substantiated.

Study Region The coast of the Emilia-Romagna Region in northern Italy consists of about 210 km of sandy beaches that have been attracting tourists for decades. Since the 1980s, erosion processes resulted in a remarkable beach retreat, notwithstanding the construction of several protections works. Study Focus In 2005–2006 and 2017–2020, 30 floods of two small rivers feeding the beaches of Ravenna, Fiumi Uniti and Savio, were monitored and bedload was measured with a Helly-Smith sampler. Riverbed bathymetric surveys were carried out after some selected floods to investigate the occurrence and geometry of alluvial bedforms. The dune migration method was also used to calculate bedload. Results provided by this method are very encouraging. New Hydrological insights for the Region To the authors knowledge, this field investigation on the bedload transport of small coastal rivers is the first one of this kind in the Adriatic and provides the regional land managers with a useful tool to predict the bedload yield for future scientifically based interventions, and hopefully successful, beach protection works. The bedload data indicate a higher variability of bedload for discharges lower than bankfull flow, whereas a stronger control of discharge is evident for larger floods. Though the bedload of the study rivers proved to be higher than in the largest river of the Region, it resulted rather low and witnesses sediment supply-limited conditions.

Vegetation cover is an important factor controlling erosion and sediment yield. Therefore, its effect is accounted for in both experimental and modelling studies of erosion and sediment yield. Numerous studies have been conducted to account for the effects of vegetation cover on erosion across spatial scales, however, little has been conducted across temporal scales. This study investigates changes in vegetation cover across multiple temporal scales in Eastern Cape, South Africa and how this affects erosion and sediment yield modelling in the Tsitsa River catchment. Earth observation analysis and sediment yield modelling are integrated within this study. Landsat 8 imagery was processed, and Normalised Difference Vegetation Index (NDVI) values were extracted and applied to parameterise the Modified Universal Soil Loss Equation (MUSLE) vegetation (C) factor. Imagery data from 2013–2018 were analysed for an inter-annual trend based on reference summer (March) images, while monthly imagery for the years 2016–2017 was analysed for intra-annual trends. The results indicate that the C exhibits more variation across the monthly timescale than the yearly timescale. Therefore, using a single month to represent the annual C factor increases uncertainty. The modelling shows that accounting for temporal variations in vegetation cover reduces cumulative simulated sediment by up to 85% across the inter-annual and 30% for the intra-annual scale. Validation with observed data confirmed that accounting for temporal variations brought cumulative sediment outputs closer to observations. Over-simulations are high in late autumn and early summer, when estimated C values are high. Accordingly, uncertainties are high in winter when low NDVI leads to high C, whereas dry organic matter provides some protection from erosion. The results of this study highlight the need to account for temporal variations in vegetation cover in sediment yield estimation but indicate the uncertainties associated with using NDVI to estimate C factor.

International audience; Soil erosion is one of the main environmental threats affecting the Critical Zone (CZ) and thus ecosystem services and human societies. Through time, physical erosion is linked to both climate

Evaluation of the vegetation and agricultural-management factor (C-factor) is an important task, the solution of which affects the correct assessment of the intensity of soil erosion. For the vast area of the European part of Russia (EPR), this task is particularly relevant since no products allow taking into account the C-factor. An approach based on automated interpretation of the main crop groups based on MODIS satellite imaging data from Terra and Aqua satellites with the LSTM machine-learning method was used to achieve this goal. The accuracy of crop group recognition compared to the open data of the Federal State Statistics Service of Russia was 94%. The resulting crop maps were used to calculate the C-factor for each month of a particular year from 2014 to 2019. After that, summaries were made at the regional and landscape levels. The average C-factor value for the EPR was 0.401, for the forest landscape zone 0.262, for the forest-steppe zone 0.362, and for the steppe zone 0.454. The obtained results are in good correlation with the results of previous field studies and provide up-to-date (based on 2014–2019 data) estimates of C-factor for rainfall erosion (monthly, annual) with high spatial detail (250 m).

The tropics are naturally vulnerable to watershed erosion. This region is rapidly growing (projected to be 50% of the global population by 2050) which exacerbates erosional issues by the subsequent land use change. The issue is particularly of interest on the many (~45,000) small tropical (2) islands, and their >115M residents, where ecotourism and sediment intolerant ecosystems such as coral reefs are the main driver of their economies. However, vulnerability to erosion and deposition is poorly quantified in these regions due to the misclassification or exclusion of small islands in coarse global analyses. We use the only vulnerability assessment method that connects watershed erosion and coastal deposition to compare locally sourced, high-resolution datasets (5 x 5 m) to satellite-collected, remotely sensed low-resolution datasets (463 x 463 m). We find that on the island scale (~52 km2) the difference in vulnerability calculated by the two methods is minor. On the watershed scale however, low-resolution datasets fail to accurately demonstrate watershed and coastal deposition vulnerability when compared to high-resolution analysis. Specifically, we find that anthropogenic development (roads and buildings) is poorly constrained at a global scale. Structures and roads are difficult to identify in heavily forested regions using satellite algorithms and the rapid, ongoing rate of development aggravates the issue. We recommend that end-users of this method obtain locally sourced anthropogenic development datasets for the best results while using low resolution datasets for the other variables. Fortunately, anthropogenic development data can be easily collected using community-based research or identified using satellite imagery by any level of user. Using high-resolution results, we identify a development trend across St. John and regions that are both high risk and possible targets for future development. Previously published modeled and measured sedimentation rates demonstrate the method is accurate when using low-resolution or high-resolution data but, anthropogenic development, watershed slope, and earthquake probability datasets should be of the highest resolution depending on the region specified.

Various large-scale risk maps show that the eastern part of Austria, in particular the Pannonian Basin, is one of the regions in Europe most vulnerable to wind erosion. However, comprehensive assessments of the severity and the extent of wind erosion risk are still lacking for this region. This study aimed to prove the results of large-scale maps by developing high-resolution maps of wind erosion risk for the target area. For this, we applied a qualitative soil erosion assessment (DIN 19706) with lower data requirements and a more data-demanding revised wind erosion equation (RWEQ) within a GIS application to evaluate the process of assessing wind erosion risk. Both models defined similar risk areas, although the assignment of severity classes differed. Most agricultural fields in the study area were classified as not at risk to wind erosion (DIN 19706), whereas the mean annual soil loss rate modeled by RWEQ was 3.7 t ha−1 yr−1. August was the month with the highest modeled soil loss (average of 0.49 t ha−1 month−1), due to a low percentage of vegetation cover and a relatively high weather factor combining wind speed and soil moisture effects. Based on the results, DIN 19706 is suitable for a general classification of wind erosion-prone areas, while RWEQ can derive additional information such as seasonal distribution and soil loss rates besides the spatial extents of wind erosion.

Detecting coastal morphodynamics is a crucial task for monitoring shoreline changes and coastal zone management. However, modern technology viz., Geoinformatics paves the way for long-term monitoring and observation with precise output. Therefore, this study aimed to produce explicit shoreline change maps and analyze the historical changes of the coastline at the east coast of the Ampara District in Sri Lanka. The histogram threshold method is used to extract data from satellite images. The time-series satellite images, acquired from 1987 to 2017, toposheet, and Google Earth historical images were compared having adjusted with the ground-truth to find the seashore changes in the study area. The histogram threshold method is used on band 5 (mid-infrared) for separating land from water pixels which means that the water pixel values were classified to one (1) and land pixel values to zero (0). The extracted shoreline vectors were associated with each other to determine the dynamics of changing shoreline of the study area. The Digital Shoreline Analysis System (DSAS) was used to find shoreline movements for each period of time. As a result, it was observed by the cross-section analysis within 100 m shoreline—seaward range along the study area—in which severe erosion has occurred northward of the Oluvil Harbor and anomalous accretion southward of the harbor because of the breakwaters constructed in the port entrance which hinder the long shore sediment transport along the study area. This situation has resulted in many ramifications to the coastal zone of the study area in socio-economic and environmental aspects in which the coastal protection mechanisms have not been well implemented to curb such issues.

International audience; The Lena, a large river that drains the northern coldest region of the Northern Hemisphere, is deeply influenced by the continuous permafrost and degradation of the frozen ground has been shown to be the main cause of the marked increase in water discharge. The first objective of this study conducted on the middle Lena was to analyze the island dynamics for the last 50 years (1967 to 2017). Several morphological parameters were surveyed using a GIS on seven series of aerial photographs and satellite images of a 100 km-long reach: island size, eroded and deposited areas, position and morphology of the islands. This approach enabled the identification of evolutionary models. Our second objective was to evaluate the potential impact of ongoing climate change. We analyzed 2 morphological parameters with respect to two main factors: efficient discharge (bar-full, bankfull and flood discharges) and water temperature. A potential erosion index (PEI) was calculated by coupling the duration of discharge exceeding the bar-full level and water temperature. The results identified several morphological changes that occurred at the end of the 20th century: an increase in the number of islands, greater eroded surfaces and accelerated migration of islands. Comparing the dynamics of islands with and without permafrost is a good indicator of their sensitivity to climate change. A major change was observed concerning the erosion and migration of islands with and without permafrost. This evolution seems to be linked both with the duration of the discharge that exceeds the bar-full level and with the number of flood peaks. The water temperature in May and August have a major influence on permafrost islands that become increasingly destabilized. Thus, as large rivers are assumed to slowly react to climate change, the recent changes in the Lena River prove that the global change deeply impacts periglacial rivers.

Biancana badlands are peculiar landforms in the Basilicata region of Italy resulting from the local combination of geological, geomorphological, and climatic settings. The evolution of badlands mainly depends on slope erosion, which is controlled by the angle, exposure, and vegetation of the slope and its interactions with insolation, rain, and wind. Multi-temporal, detailed, high-resolution surveys have led researchers to assess changes in slopes to investigate the spatial distributions of erosion and deposition and the influence of wind-driven rain (WDR). A comparison between two terrestrial laser scanner (TLS) point clouds surveyed during 2006 and 2016 fieldwork showed that the study area suffers from intense erosion that is not spatially uniform on all sides of biancane. By combining slope and exposure data and the cloud of difference (CoD), derived from a 3D model, we showed that all the steepest southern sides of biancane suffered the most intense erosion. Because splash and sheet erosion triggers sediment displacement, the analysis was also focused on the intensity and direction of WDR. We performed a real field experiment analysing erosion rates over 10 years in relation to daily and hourly wind data (direction and speed), and we found that frequent winds of moderate force, combined with moderate to heavy rainfall, contributed to the observed increase in soil erosion when combined with the insolation effect. Our results show how all the considered factors interact in a complex pattern to control the spatial distribution of erosion.

The Tibetan Plateau, also known as the “Water Tower of Asia” because of its function as a water storage and supply region, responds dramatically to modern climate changes. Paleoecological shifts inferred from lake sediment archives provide essential insights into past climate changes, and the processes that drove those shifts. This is especially true for studies of lakes in endorheic basins on the Tibetan Plateau, where lake level is regulated predominantly by Monsoon intensity. Such water bodies provide excellent opportunities to reconstruct past changes in humidity. Most paleolimnological investigations of lakes on the Tibetan Plateau, however, have involved the study of a single sediment core, making it difficult to discern between changes caused by local events and those caused by lake-wide or regional processes. Here we present results from a paleolimnological study of Lake Taro Co, a currently closed-basin lake in Central Tibet. We compared a sediment record from the central part of the lake to a record from the near-shore area, and present results of sedimentological and bioindicator (chironomid, diatom, pollen) analyses from both records. Results show three periods of lake-wide ecosystem change (> ca. 5250, 5250–2250 and, Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347, Fellowships for Young International Scientists http://dx.doi.org/10.13039/501100010895, NSFC Research Fund for International Young Scientists (CN), Deutsche Forschungsgemeinschaft (DFG) (DE), National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809, Technische Universität Braunschweig (1042)

Wildfire heavily impacts the quality of forest soils, and the precipitation occurring immediately after fire can determine high runoff and erosion rates, which may lead to noticeable soil degradation. Mulching is commonly used to limit the hydrological impacts of wildfire and climate, but this post-fire management technique may alter the erosion–deposition dynamics at the hillslope scale and, consequently, alter soil quality. In order to explore the magnitude and significance of these changes (little was studied in the literature until now), this communication reports the first results of a field activity that evaluated the changes in soil quality in areas affected by a wildfire and subjected to different post-fire treatments in Mediterranean forests. The main properties of sediments eroded from burned and untreated soils, and mulched soils (using a straw dose of 0.2 kg/m2 of dry weight), were measured after the first rainstorm (height of 37 mm and maximum intensity of 11.6 mm h−1) occurring two months after a wildfire (occurred on 30 June 2016) in a pine forest of Castilla-La Mancha (Spain). This event produced a runoff volume of 0.07 ± 0.02 mm in mulched soils and 0.10 ± 0.10 mm in non-mulched soils; soil loss was 0.20 ± 0.06 g/m2 in the mulched area and 0.60 ± 0.60 g/m2 in the non-mulched area. In comparison to burned and non-treated areas, this study showed: (i) increases in salinity, and reductions in organic matter, nutrients, nitrates, and micro-elements in burned and untreated soils; (ii) reductions in runoff (−20%) and in soil erosion (−60%) as a result of mulch cover; (iii) effectiveness of mulching in limiting the declines in soil quality detected in burned and eroded areas; and (iv) transport of low amounts (less than 10–15%) of some compounds (organic matter and nutrients) downstream of the fire-affected areas (both mulched and untreated). Phosphorous runoff toward valley areas and nitrate incorporation into the soil, detected in both mulched and untreated areas, require attention, since these processes may cause eutrophication of water bodies or nitrate pollution in groundwater.

Purpose Loess landscapes are highly susceptible to soil erosion, which affects soil stability and productivity. Erosion is non-linear in time and space and determines whether soils form or degrade. While the spatial variability of erosion is often assessed by either modelling or on-site measurements, temporal trends over decades to millennia are very often lacking. In this study, we determined long- and short-term erosion rates to trace the dynamics of loess deposits in south-western Poland. Materials and methods We quantified long-term (millennial) erosion rates using cosmogenic (in situ 10Be) and short-term (decadal) rates with fallout radionuclides (239+240Pu). Erosion processes were studied in two slope-soil transects (12 soil pits) with variable erosion features. As a reference site, an undisturbed soil profile under natural forest was sampled. Results and discussion The long-term erosion rates ranged between 0.44 and 0.85 t ha−1 year−1, whereas the short-term erosion rates varied from 1.2 to 10.9 t ha−1 year−1 and seem to be reliable. The short-term erosion rates are up to 10 times higher than the long-term rates. The soil erosion rates are quite consistent with the terrain relief, with erosion increasing in the steeper slope sections and decreasing in the lower parts of the slope, while still maintaining high values. Conclusions Soil erosion rates have increased during the last few decades owing to agriculture intensification and probably climate change. The measured values lie far above tolerable erosion rates, and the soils were found to be strongly imbalanced and exhibit a drastic shallowing of the productive soils horizons., Journal of Soils and Sediments, 21 (8), ISSN:1439-0108, ISSN:1614-7480

Peatlands are one of the largest terrestrial carbon sinks on the planet, yet little is known about carbon accumulation rates (CARs) of mountainous examples. The long-term variability in the size of the associated carbon sink and its drivers remain largely unconstrained, especially when long-term anthropogenic impact is also considered. Here we present a composite CAR record of nine peatlands from central-eastern Europe (Romania and Serbia) detailing variability in rates of carbon accumulation across the Holocene. We show examples of extremely high long-term rates of carbon accumulation (LORCA > 120 g C m−2 yr−1), indicating that at times, mountain peatlands constitute an efficient regional carbon sink. By comparing our data to modelled palaeoclimatic indices and to measures of anthropogenic impact we disentangle the drivers of peat carbon accumulation in the area. Variability in early and mid-Holocene CARs is linked to hydroclimatic controls, with high CARs occurring during the early Holocene and lower CARs associated with the transition to cooler and moister mid-Holocene conditions. By contrast, after 4000 years (calibrated) before present (yr BP) the trends in CARs indicate a divergence from hydroclimate proxies, indicating that other processes became the dominant drivers of peat CARs. We suggest that enhanced erosion following tree cover reduction as well as enhanced rates of long-distance atmospheric dust fallout might have played a role as both processes would result in enhanced mineral and nutrient supply to bog surfaces, stimulating peat land productivity. Surprisingly though, for the last 1000 years, reconstructed temperature is significantly correlated with CARs, with rising temperatures linked to higher CARs. We suggest under future climate conditions, predicted to be warmer in the region, peat growth may expand, but that this is entirely dependent upon the scale of human impact directly affecting the sensitive hydrological budget of these peatlands.