Vertical Erosion Research Articles

Experiments on Constriction‐Pool‐Widening Morphology in Bedrock Canyons

AbstractBedrock rivers often alternate between relatively wide unconstrained reaches and conspicuously narrow deep incised bedrock reaches (canyons). These bedrock canyons exhibit a constriction‐pool‐widening (CPW) morphology that consists of a lateral constriction, a deeply scoured pool formed downstream of the constriction, and a channel widening at or near the pool exit. To explore how CPWs are formed in bedrock canyons, we hypothesize that the lateral constriction at the canyon entrance forces a CPW to form allogenically with subsequent CPWs propagating further downstream. Our hypothesis was tested experimentally in a flume channel with a forced lateral constriction at the canyon entrance. Our experiment shows that the forced constriction can cause a primary CPW to form allogenically because the backwater upstream of the forced constriction causes sediment deposition that creates an elevation drop, promoting flow and sediment to plunge toward the bed and carve a primary pool. Channel widening occurs at the primary pool exit because sediment deposit forms that deflects sediment into the banks, causing lateral erosion. Downstream of the primary widening, channel width declines and a new lateral constriction forms, which causes the formation of pools and widening downstream, resulting in downstream CPW propagation. In our experiment, the bedrock channel evolved until a persistent alluvial cover formed, reaching a steady state morphology without further vertical erosion until perturbed by higher discharge. Our experiment shows that discharge variation is necessary for a channel to evolve in the absence of uplift.

The influence of erosion on the dynamic process of landslide in Xinmo Village, Maoxian

A large-scale, high-speed, long-runout landslide occurred in Xinmo Village, Maoxian, Sichuan Province, China, on June 24, 2017. It was characterized by fast sliding speed, rapid volume growth, and large impact area. The dynamic process of such landslides and the influence of erosion on the dynamic process are studied by field investigation, numerical inversion and simulation. The results showed that entrainment erosion was a major factor of landslide volumetric change and a salient feature of the landslide process. An exponential equation relating the erosion rate and the deposition volume was established. Moreover, the study found that a slight change of the erosion rate (1e-4) also had a significant impact on the lateral spreading, longitudinal runout, and vertical erosion. As the erosion rate increased, the lateral spreading, longitudinal runout, and vertical erosion of this type of landslide became more obvious. By using the coefficient of variation method, it was obtained that the erosion rate had a greater influence on the vertical erosion than on the lateral spreading and longitudinal runout. In the study of the velocity of the rock avalanche under different erosion conditions, it was found that the erosion amount and the landslide velocity were not strictly linearly related. This study has important significance for understanding the dynamic process and erosion effect of rock avalanche, and provides useful references and insights for future research in related fields.

Landslide susceptibility prediction based on landform predisposing indexes − An example from the Beiluo River Basin

The Beiluo River basin, which flows through the central part of the Loess Plateau, has experienced intense soil erosion and significant geomorphic change, which has provided favorable conditions for the occurrence of a large number of landslides. Landform indexes, which can express geomorphologic development state and internal rules, can transfer the development process information of surface morphology into the evaluation of landslide susceptibility, and help get more accurate landslide susceptibility prediction results. Taking the Beiluo River Basin as an example, a landslide susceptibility prediction model based on landform index is proposed by comparing the importance of landform index. In order to improve the accuracy of LSP, 10 kinds of general predictors indexes, 5 kinds of landform predisposing indexes and 1821 landslide points were compiled, and the geographic information system of Beiluo River Basin was constructed. Through the correlation test and CF model, the environmental indexes were evaluated to obtain the sensitive index results, and the combination of different environmental predictors indexes were classified according to the sensitive index results. Based on the combined classification results, the Max Entropy (MaxEnt) model was used to evaluate the Landslide susceptibility prediction (LSP), while the calculated results were evaluated and compared using the receiver operating characteristic (ROC) curve and landslide density. The results show that the vertical erosion factor, elevation, rainfall, horizontal erosion factor, slope angle and NDVI play a key role in controlling the spatial distribution of landslides in the study area. At the same time, the accuracy of landslide susceptibility is compared by AUC value. According to the calculation results, the Group5 (AUC = 0.803) with reasonable terrain index performs better in the training and test stages, and the relative accuracy is improved by 6.22 % compared with the non-introduction of terrain index and the omission rate difference is the best (omission rate difference = 0.0005), indicating that the introduction of landform index can effectively improve the landslide susceptibility prediction. The distribution of different sensitive areas was observed. The high sensitive areas and very high sensitive areas are mainly distributed in the southern Luochuan loess tableland and the northern Wuqi loess hilly area. The research results provide a scientific basis for landslide susceptibility prediction with rational introduction of landform indexes and regional infrastructure construction.

3D large deformation modeling of the 2020 Gjerdrum quick clay landslide

A quick clay slide in Gjerdrum, Norway, occurred at 4 a.m. on 30th December 2020, killing ten people and destroying houses, roads, and other infrastructures. Approximately 1.35 million cubic meters of clay were released, a large volume liquefied, and debris was transported almost two kilometers downstream. An investigation following the slide determined that the slide was initialized in a 30-meter-high slope after 2-to-2,5-meter vertical erosion in a small creek running along the toe of the slope. After the initiation, the slide developed retrogressively in the order of 500 meters backward and sideways over a period of about 2 minutes. A conventional geotechnical slope stability analysis explains the initial slide. However, more advanced numerical tools are needed to simulate the retrogressive mechanism and the debris flow. The aim of the paper is to demonstrate a 3D Material Point Method model to capture some of the mechanisms involved from initiation until the debris comes to rest and how this method can be used to reproduce and study the processes involved in large deformation landslides.

Appraisal of active tectonics in Karangsambung Amphitheater: Insights from DEM-derived geomorphic indices and geological data

The morphology of the Karangsambung area shows a unique form, namely the morphology of the amphitheater. This area results from the complexity of tectonic, erosion, and depositional processes. The active tectonics in this region greatly influence the drainage system and geomorphic expression. The study area provides evidence of subduction in Java. It is an ideal natural laboratory for studying evidence of tectonic activity due to the subduction of the Indo-Australian plate with the Eurasian plate during the Cretaceous period. We evaluated active tectonics using the DEM to assess the characteristics of the geomorphic index. The results obtained from these indices were combined to produce an index of relative active tectonics (IRAT) using GIS. The average of the seven geomorphic indices measured was used to evaluate the distribution of relative tectonic activity in the study area. We defined four classes to determine the relative level of tectonic activity: class 1: very high (1.0 ≤ IRAT < 1.5); class 2: high (1.5 ≥ IRAT < 2); grade 3: moderate (2 ≥ IRAT < 2.5); and grade 4: low (2.5 ≥ IRAT). The results show that the study area was strongly deformed and was influenced by tectonic activity. Landsat imagery, DEM, and field observations also proved the presence of active tectonics in the form of uplift accompanied by high vertical erosion forming pointed hills with narrow valleys, the exposure of Cretaceous-aged rocks, amphitheater morphology, and the uplift of river terraces. The indicative IRAT values were consistent with the relative uplift levels, landforms, and geology.

Quantifying Morphostructural Evolution of the Eastern Algerian Saharan Atlas (NE, Algeria) Using GIS-based Surface Envelope Technique, Drainage Network Analysis, and Geological Features

This research work focuses on the morphostructural evolution of the eastern end of the Algerian Saharan atlas. The study employs a comprehensive methodology involving the utilization of the surface envelope technique, combined with an analysis of the hydrographic network and geological context. These techniques are integrated within a GIS framework to decipher the current relief characteristics. To interpret the current relief features, two ASTGTM v2 tiles were processed to extract morphometric data. The reconstruction of the original relief requires the generation of the summit level surface, the base level surface and the relief amount maps for 3 different grid sizes (4000m, 1000m and 250m). The respective different grid size maps has allowed determining the initial surface of the reliefs; first before any major vertical erosion, then after a phase of dismantling and finally the recent and sub current morphological aspect. The extraction of the hydrographic network and the elimination of lower than order 5 streams revealed the harmony of the latter with a raised shaped form (mega-horst) which represents the main morphostructural unit. This morphostructure is particularly characterized by outcrops from the Lower Cretaceous outcrops. The ramification of the hydrographic network along the main tectonic accidents has allowed the digging of wide valleys, often described as graben.

New detrital petrographic and thermochronologic constraints on the Late Cretaceous–Neogene erosional history of the equatorial margin of Brazil: Implications for the surface evolution of a complex rift margin

AbstractThe equatorial margin of Brazil is an example of a rift margin with a complex landscape, dominated by an escarpment perpendicular to the continental margin, which testifies to an equally complex rift and post‐rift surface and tectonic evolution. This has been the focus of a long debate on the driving mechanism for post‐rift tectonics and on the amount of exhumation. This study contributes to this debate with new petrographic and thermochronologic data on 152 samples from three basins, Pará‐Maranhão, Barreirinhas and Ceará, on the offshore continental platform. Our detrital record goes back to the rift time at ca. 100 Ma ago and outlines three major evolutionary phases of a changing landscape: a rift phase, with the erosion of a moderate rift escarpment, a Late Cretaceous‐Palaeogene post‐rift phase of major drainage reorganization and significant vertical erosion and a Late Oligocene‐to‐Recent post‐rift phase of moderate vertical erosion and river headwater migration. We estimate that along the equatorial margin of Brazil, over a large onshore area, exhumation since the Late Cretaceous has totalled locally up to 2–2.5 km and since the late Oligocene did not exceed 1 km.

Assessment of Flood-Induced Geomorphic Changes in Sidere Creek of the Mountainous Basin Using Small UAV-Based Imagery

Floods often cause changes in the hydro-geomorphology of riverbeds and banks. These changes need to be closely monitored to find a balance and exchange between lateral and vertical erosion and deposition, upstream local sediment supply, and a stream’s transport capacity. Low-frequency cross-sectional field surveys cannot map hard-to-reach locations. Innovative techniques, such as small unmanned aerial vehicles (UAVs), must be employed to monitor these processes. This research compared historical data with a UAV survey and the Pix4DMapper structure-from-motion (SfM) program to assess the longitudinal, lateral, and vertical changes of Sidere Creek in the eastern Black Sea, Türkiye. Digitization was undertaken using 2011–2015–2017 Google Earth photographs, 1960s topographic maps, and 2023 orthomosaics. ArcGIS 10.6 was used to delineate the centerlines (thalweg), left/right banks, alluvial bars, active channel widths, and channel confinement layers. Channel Migration Toolbox and CloudCompare were utilized for analyzing lateral and vertical morphological changes, respectively. The active channel migrated 25.57 m during 1960–2011, 15.84 m during 2011–2015, 6.96 m during 2015–2017, and 5.79 m during 2017–2023. Left-bank channel confinement rose from 2.4% to 42% and right-bank channel confinement from 5.9% to 34.8% over 63 years. Neither stream meandering nor sinuosity index changed statistically. Active channel boundary widths varied from 149.79 m to 9.46 m, averaging 37.3 m. It can be concluded that UAV surveys can precisely measure and monitor the stream channel longitudinal, lateral, and vertical morphological changes at a lower cost and in less time than previous methods.

Analyzing drainage basin orientation and its relationship to active fold growth (Handun anticline, Zagros, Iran)

Combinations of tectonic geomorphological criteria are frequently used to detect vertical and lateral growth of fold structures in tectonically active settings due to their low cost and relative ease of application. The purpose of this study is to analyze the morphometric properties of drainage basins developed into the flanks of a growing anticline to explore the active tectonic growth patterns of the fold. We target the Handun anticline in the Zagros Simply Folded Belt due to it being an actively growing fold structure with a high variability of drainage basin morphologies across different parts of the fold.57 drainage basins were characterized in terms of their orientation using a newly defined drainage basin orientation (DBO) index, in combination with a set of standard tectonic geomorphological metrics (drainage basin area [Ba], slope [S], asymmetry factor [AF], hypsometric integral [HI], basin shape [Bs], crescentness index [CI], sinuosity of the main drainage [Smd], drainage density [Dd], drainage density of 1st-order streams [Dd1], drainage frequency [Df] and sinuosity of anticline divide [Sad]). Indices were synthesized for spatial comparison between western, central and eastern zones of the growing fold.Results show that the DBO is strongly correlated with its CI, Smd, and Ba. In terms of spatial distribution, the central zone is characterized by higher values of DBO, Ba, S, CI, Smd, and Sad. These contrast with the western and eastern zones (fold plunge regions), which are characterized by higher values of Dd, Dd1, and Df. Of note is the southern limb of the anticline, which is characterized by larger drainage basins, and higher values of AF, CI, and Smd. This suggests higher lateral erosion on the southern fold flank. In contrast, drainage basins with steeper S, and greater DBO and elongation are found on the northern limb, suggesting dominance of vertical erosion. This contrasting south-north erosion pattern suggests that the northern fold flank is actively steepening, and presenting a more youthful topography, with lower and spatially focused erosion that is increasing with time. Overall, high values of the newly proposed DBO metric relate to the presence of a curved and/or an asymmetric forked drainage pattern, and also to the trend of faults and fractures across the fold. These structures are typically oriented oblique to the fold axis, with further modification into a semi-annular drainage pattern developed around a salt diapir.

The development of sand erosion induced by shield-tunnel joint leakage

Sand erosion induced by shield-tunnel joint leakage is one of the most frequent catastrophes, causing ground collapses and tunnel failures. In this paper, a self-designed test device that considers differences in water head, burial depth and leaky joint characteristics was used to investigate sand erosion and void development. The experimental results show that the development of sand erosion has obvious temporal and spatial evolution characteristics. In the temporal dimension, sand erosion development can be divided into four stages: vertical erosion, cavity formation, coarse-particle skeleton distribution (CPSR) and steady seepage. In the spatial dimension, it can be divided into three regions: the stable zone, slip surface and eroded zone shape. It is found that the erosion zone can be described by a rotating ellipsoid and the scope of the erosion zone increases with increasing water head, whereas the influence of the burial depth is not significant. The influence of the invert leakage on the volume flow rate is also determined to be larger than that of the vault leakage and the volume flow rate rapidly increases when the size of the leaky joint exceeds the critical outlet size. Finally, a theoretical model based on the test results is proposed to predict the volumetric flow rate of sand erosion.

Experimental Investigation into the Erosion Performance of Water Jets on Marine Hydrate-Bearing Sediment

Fine-grained natural gas hydrate (NGH) reservoirs are widely distributed across the world and bear more than 90% of global NGH. However, it is difficult to exploit this kind of NGH reservoir economically and environmentally using conventional methods. Water-jet cutting is an efficient and environmentally friendly technique for mining such hydrate reservoirs, as the production process does not depend on mass and heat transfer within the formations. In this work, a series of physical experiments were conducted to clarify the erosion performance of marine hydrate-bearing sediment (HBS) impacted by water jets. The results show that the accumulation of sediment particles and hydrate particles at the bottom of erosion hole severely inhibits the vertical erosion of HBS by water jet. For a particular jet flow rate, the jet distance has an optimal value, which is between 4 mm and 28 mm. Moreover, the upwelling flow containing solid particles has a significant impact on the erosion of the hole top. In reservoirs with a low hydrate saturation (20–40%) and reservoirs with a high hydrate saturation (60–80%), the erosion holes exhibit a gourd shape and a bamboo shape, respectively. In addition, the volume erosion efficiency and the depth erosion efficiency are more sensitive to the variation in jet flow rate than jet distance and hydrate saturation. This study can provide theoretical and technical support for the application of water-jet cutting in the exploitation of marine HBS.

Sediment erodibility in the Changjiang (Yangtze) subaqueous delta: spatial–temporal distribution and sedimentary significance

Delta evolution in the context of no sediment discharge has become a global concern, and an accretion-to-erosion conversion is occurring in the Yangtze estuary. This conversion could threaten Changjiang subaqueous delta development. Sediment erodibility is an important indicator of subaqueous delta vulnerability. However, the present and future erodibility of the Changjiang subaqueous delta remains unclear. In this study, 37 short cores were collected from the Changjiang subaqueous delta, and the critical shear stress of the sediment was measured using a cohesive strength meter (CSM) and compared with estimates based on an empirical Shields diagram. The sediment erodibility was analyzed by comparing the sediment critical shear stress with the bed shear stress simulated using a numerical model (i.e., FVCOM), and sediment activity was introduced to discuss the geomorphological change in the subaqueous delta. The CSM-derived critical shear stress is significantly higher than that derived from the empirical Shields formula, but it better shows the erodibility of the sediment. The annual surface sediment activity ranges from 5% to 30% based on the CSM, indicating low surface erodibility. Moreover, the critical shear stress in this region increases as water depth increases, but the bed shear stress shows the opposite trend. Therefore, the erodibility of the Changjiang subaqueous delta is lower than that of the shallow area, indicating no accretion-erosion conversion or continued vertical erosion under sediment starvation in the coming decades. These findings can provide suggestions for erosion assessment and management in large river deltas under decreasing sediment discharge.

Pore characteristics and micro-structure change of undisturbed loess induced by acid corrosion

With the rapid development of coal chemical base and urbanization construction in China's Loess Plateau, the phenomenon of acid corrosion induced loess geological disasters tends to occur frequently in this region. Loess is characterized by high water sensitivity, dense vertical joint surface, and rich in carbonate minerals, which providing a good precondition for acid solution corrosion. Due to the occurrence of chemical erosion, the changes of loess structure and strength become more complex, and there is a significant difference from the conventional water infiltration-induced loess disasters. In order to clearly grasp the internal mineral and structural damage characteristics of loess under acid dissolution conditions, this work studies the pore characteristics and micro-structure change of undisturbed loess under acid corrosion conditions with different pH values (7, 5 and 3) and dissolution times (5,10 and 15 days). It is found that the content of carbonate minerals in the undisturbed loess,and the combined structure characteristics are the two main factors affecting its acid corrosion effect. Specific findings include as: (1) With the decrease of pH, the dissolution of carbonate minerals such as calcite and dolomite intensifies (the element content of the precipitate: Ca96.58%, Mg1.26%), and the selective dissolution of silicate minerals (albite and chlorite) are obvious, which provides expansion space for pores. As a result, the change of the pore structure of undisturbed loess by acid leaching is as follows: Expansion of initial joints→Connectivity and enlargement of internal pores→The increase of new shallow pores. Meanwhile, under the action of acid dissolution, the cohesive substances were rearranged due to the dissolution, disintegration and rotation of the skeleton particles during the collapse, resulting in an increasing in the content of fine particles in the soil. (2) With the increase of corrosion time, the roundness increased from 7.19 to 25.98 which proves that the contact between the acid solution and mineral particles is more complete, and the effect of corrosion and particle aggregation is more significant. This results in a reciprocating unidirectional development of the pore structure. Flocculated particles with clay properties appear alternately in the soil structure. (3)The occurrence of acid-sensitive geological disasters in loess is mainly divided into three stages: The filling of the structural surface is eroded by acid→The horizontal and vertical erosion is intensify→The soil is broken down into particles that are washed away. This study has a certain reference for understanding the damage mechanism and early warning of loess eroded by acid solution in China's Loess Plateau.

Connecting science and community: Volunteer beach profiling to increase coastal resilience

The New Hampshire (NH) Volunteer Beach Profile Monitoring Program (VBPMP) was developed as a partnership between University of New Hampshire scientists, community volunteers through the Coastal Research Volunteer program, the NH Coastal Program, and the NH Geological Survey. The program addresses multiple needs including building a robust dataset to understand beach erosion and accretion trends on the New Hampshire Atlantic Coast and developing the capacity to maintain the program over an extended period (years). Also, very important to the program is the engagement of local and regional residents in the study as partners and sharing the results to increase awareness of coastal issues to inform coastal management. Starting in December 2016, three profile stations were established at three NH beaches to train volunteers and establish the monitoring program. In January 2018, the number of profile stations was expanded to thirteen, increasing coverage to six major beaches.. Analysis of the beach profile database focuses on the period from January 2018 to October 2021. As expected, NH beaches showed seasonal variations with erosion in winter followed by extended accretional periods. The beaches were significantly eroded during a series of severe nor'easters in March 2018. For example, Hampton Beach experienced up to ∼1.4 m of vertical erosion and ∼30 m of berm retreat. An unexpected result from this study was the large differences in the mean elevations between the beaches based on the elevation profiles. The lower elevation beaches were far more susceptible to storm flooding, erosion, and damage to infrastructure. In addition to greater capacity for data collection toward decision-making, adopting a citizen science approach resulted in benefits to community and academic partners, such as improved methods, varied perspectives, increased knowledge about coastal processes and climate threats, connection to place, and motivation to take action.

Experiments on Pool Formation in Bedrock Canyons

AbstractRivers cut into rock exhibit a wide range of morphologies that do not occur in alluvial rivers. The reach‐scale morphology of bedrock canyons has not been widely explored. Many rivers bound by rock on both banks exhibit a constriction‐pool‐widening morphology characterized by a lateral channel constriction, a deeply scoured pool that typically forms downstream of the constriction, and a channel widening coincident with the scour pool. Lateral constrictions are thought to cause plunging flows that carve pools which then shallow and widen downstream. A flume experiment was conducted to test this hypothesis. Experiments show that flow deceleration upstream of the constricted canyon promotes alluviation. Flow acceleration through the canyon prevents persistent alluvium from developing before a pool is formed. At the canyon entrance, flow and sediment plunge toward the bed, creating a primary scour pool. The primary scour pool reaches equilibrium morphology for a given constant discharge and sediment supply by cutting a slot, which then gets deep enough to maintain a permanent alluvial cover, protecting the pool from further vertical erosion. Downstream of the primary pool, an alluvial cover intermittently develops that causes flow to plunge, carving secondary pools. Shear stresses are counterintuitively large in alluviated areas and low in places where the bed is clear of sediment. However, near‐bed velocity was strongly correlated with alluviation patterns and erosion rate, suggesting near‐bed velocity may be a more practical way to calculate rock erosion rates in non‐uniform flows.

Surface Elevation Changes Estimation Underneath Mangrove Canopy Using SNERL Filtering Algorithm and DoD Technique on UAV-Derived DSM Data

Estimating surface elevation changes in mangrove forests requires a technique to filter the mangrove canopy and quantify the changes underneath. Hence, this study estimates surface elevation changes underneath the mangrove canopy through vegetation filtering and Difference of DEM (DoD) techniques using two epochs of unmanned aerial vehicle (UAV) data carried out during 2016 and 2017. A novel filtering algorithm named Surface estimation from Nearest Elevation and Repetitive Lowering (SNERL) is used to estimate the elevation height underneath the mangrove canopy. Consequently, DoD technique is used to quantify the elevation change rates at the ground surface, which comprise erosion, accretion, and sedimentation. The significant findings showed that region of interest (ROI) 5 experienced the highest volumetric accretion (surface raising) at 0.566 cm3. The most increased erosion (surface lowering) was identified at ROI 8 at −2.469 cm3. In contrast, for vertical change average rates, ROI 6 experienced the highest vertical accretion (surface raising) at 1.281 m. In comparison, the most increased vertical erosion (surface lowering) was spotted at ROI 3 at −0.568 m. The change detection map and the rates of surface elevation changes at Kilim River enabled authorities to understand the situation thoroughly and indicate the future situation, including its interaction with sea-level rise impacts.

Morphology, sedimentology and origin of an anomalous cut-off along the Pravara river, deccan trap region, India

River meanders have always been an intriguing subject in fluvial geomorphology because of their ubiquity, dynamism, remarkable forms and practical consequences of their movement. Sometimes a relatively straight channel flowing over bedrock may develop a lone meander bend cut-off which is very out of the place from the surrounding area. The occurrence of a sudden bend along a river may not be a meandering bend but may be manifestation of sudden change in the river dynamism due to many reasons, such as, lithology, change in rainfall regime, tectonics etc. The formation of such features highlights the behavior of river in the past. One such striking feature has been observed along the River Pravara in the Deccan Trap Region, Maharashtra, India. Rivers in Deccan Trap Region do not meander and form cut-offs by rule. It is rocky country where rivers flow in deeply incised bedrock. Hence, the observed feature displays a striking anomaly in this region. Hence, an attempt has been made in the present paper to evaluate the mode of formation of this single cut-off along this channel. Morphological and sedimentological data were generated and analyzed for the channel loop and the link channel to understand the competence of the river in the past and present which were directly or indirectly responsible for the development of this channel anomaly in this reach. Based on the results of the analysis and intensive field observations, it has been inferred that this is a classic example of natural morphological adjustment of a river when a set of events occurred, first retardation of vertical erosion encountering bedrock followed by series of floods to induce the channel to divert from the original path to resume the present course. Presence of a tributary further aided to the process of the loop development. The study can provide additional knowledge to the studies involving anomalous channel cut-offs at any part of the world.

Escarpment retreat rates derived from detrital cosmogenic nuclide concentrations

Abstract. High-relief great escarpments at passive margins present a paradoxical combination of high-relief topography but low erosion rates suggesting low rates of landscape change. However, vertical erosion rates do not offer a straightforward metric of horizontal escarpment retreat rates, so we attempt to address this problem in this paper. We show that detrital cosmogenic nuclide concentrations can be interpreted as a directionally dependent mass flux to characterize patterns of non-vertical landscape evolution, e.g., an escarpment characterized by horizontal retreat. We present two methods for converting cosmogenic nuclide concentrations into escarpment retreat rates and calculate the retreat rates of escarpments with published cosmogenic 10Be concentrations from the Western Ghats of India. Escarpment retreat rates of the Western Ghats inferred from this study vary within a range of hundreds to thousands of meters per Myr. We show that the current position and morphology of the Western Ghats are consistent with an escarpment retreating at a near-constant rate from the coastline since rifting.

Gravel Mining Activity Impact on Riverbed Erosion and Bridge Foundation Stability

Geomorphological processes pose a risk that deserves attention and planning to avoid that, especially in the section near to east of Tuz bridge. This section of the valley facing a dramatic increase in gravel excavation and sorting of aggregates, consequence led to a change in the pattern of river branches flow from an anabranching river to a single-channel river, which led to a concentration of river discharge during floods. On 9th December 2018, Tuz Bridge was failed due to a heavy rainstorm three days preceding the failure event. The current study aims to conduct a field survey of all the human activities in the study area to assess river changes from remote sensing data the amount of runoff and river peak discharge based on rainfall data using SCS-CN method. In this study, ArcGIS, ArcGIS Earth, Google Earth, and WMS software are incorporated in the data analysis. The revealed results indicate the severe modification of valley morphology and converting the river pattern to flow during flood within a single channel with flow speed exceeded the critical velocity to induce vertical erosion of gravel and sands under the foundations of the bridge and causing the displacement and settlement of the bridge. The study recommends the local administration prevent gravel mining from the river valley at the upstream area of the bridge

Anthropogenic influences on the variation of runoff and sediment load of the Mahanadi River basin

ABSTRACT The emphasis of the present study is on trends and abrupt change points for the runoff and sediment load in a major river basin and anthropogenic factors that influence these trends. The methods adopted are the Mann-Kendall, Sen’s slope, and Pettitt tests for trend and change detection; the difference in digital elevation model for coastal morphological changes; and the double mass curve technique for relative proportions of anthropogenic factors. Significant decreasing trends in yearly runoff and sediment load are observed for 13% and 69% of the hydrological stations, respectively. The analysis found a 79% reduction in sediment discharge into the sea. A figure showing zones of vertical erosion and accretion is also displayed. Geomorphic changes indicate that the landforms susceptible to areal erosion are vulnerable to vertical land loss. Upstream damming, increasing demand, and water allocations are the crucial anthropogenic factors responsible for reducing the sediment load of the basin.