Erosion Level Research Articles

Study on the Morphological Distribution and Modeling Methods of River Particles in Upstream and Downstream Sections

This study investigates the morphological evolution of river particles and their mechanical behavior during sediment transport. River particles exhibit distinct shape differences between upstream and downstream sections, with particles becoming progressively rounded downstream. The rounding process is quantitatively described using morphological indices. The analysis reveals upstream particles are more angular, while downstream particles become increasingly rounded due to erosion and abrasion, modeled by a unified abrasion function. The Loop subdivision method effectively simulates this gradual rounding process. Additionally, the Discrete Element Method (DEM) calculates the natural angle of repose for particles with varying erosion levels, showing angles ranging from 38.2° for angular particles to 34.4° for rounded particles, closely matching field observations. The numerical results effectively demonstrate the interlocking effect caused by particle morphology. This research enhances the understanding of sediment transport dynamics and provides a robust framework for modeling particle shape evolution.

Spatio-temporal soil loss modelling using RUSLE and sediment delivery into a reservoir in a semi-arid region of northern Nigeria

Soil loss is aggravated by uncontrolled deforestation, indiscriminate land clearing for agricultural activities, overgrazing, and urban development that leads to severe soil erosion over the land surface. The main objective of this research is to apply the Revised Universal Soil Loss Equation (RUSLE), in conjunction with remote sensing and GIS, to determine the temporal variation of soil loss from the Gubi watershed in the years 2000 and 2017 and to estimate the sediment delivery into the Gubi reservoir in Northern Nigeria. Datasets of rainfall, soil type, topography, cover management, and support practice were utilized to determine the five RUSLE factors. The research identified five levels of erosion ranging from severe to very low-risk areas. The spatial distribution of erosion hotspots in the catchment area was highlighted. Results revealed increasing levels of erosion from 14,244.31 tons/year in 2000 to 16,792.33 tons/year in 2017. Consequently, the catchment's sediment yield was 6903.65 tons/year and 9172.71 tons/year corresponding to sediment delivery ratios of 48.46 % and 54.62 % in 2000 and 2017 respectively. The sediment inflow into Gubi reservoir was 747.38 tons/year and 950.76 tons/year corresponding to 10.83 % and 10.37 % of the total sediment yield in 2000 and 2017 respectively. Soil erosion vulnerability index maps were produced and the erosion is expected to increase with time as agricultural activities and deforestation continue to occur. The sediment deposits have the potential to reduce the designed life of the reservoir. Best management practices, such as tree planting, mulching, and contour ridging are recommended for soil conservation. There is a need to assess the reservoir sediment deposits so that measures can be taken to maintain the reservoir operations properly.

Response of estuarine morphology to storm surge barriers, closure dams and sea level rise

Storm surge barriers and closure dams influence estuarine morphology. Minimizing consequential ecological impacts requires a thorough understanding of the morphological adaptation mechanisms and associated time scales. Both are unraveled using three decades of morphological measurements on the adaptation of the Eastern Scheldt estuary (The Netherlands) to a storm surge barrier and closure dams. Both the storm surge barrier (through a decrease in cross-sectional area) and closure dams (inducing a reduction in surface area of the estuary) contributed to a reduction in tidal prism. As a smaller tidal prism implies a smaller equilibrium volume of the channels, the channels demand sediment to adjust. Consequently, by providing sediment to the channels, the intertidal flats erode. Erosion rates decreased while the sediment demand of the channels attenuated. This attenuation in sediment demand resulted mainly from tidal prism gains, caused by intertidal flat erosion and sea level rise. Erosion rates of the intertidal flats decreased further while they flattened to adapt to the reduced tidal velocities. Furthermore, storms caused erosion events, after which the long-term adaptation pace of intertidal flats suddenly reduced. Despite decreasing erosion, sea level rise enhances the drowning of intertidal flats in sediment-scarce estuarine systems, thereby pressuring these estuarine ecosystems and raising the need for mitigation measures.

SOIL NUTRIENT ENRICHMENT IN THE INDIAN SUBCONTINENT WITH MATHEMATICAL INTERPRETATIONS: MISTRAL ALGORITHM

Soil consists of particulate matter like loose earth, minerals, and essential nutrients, all required to cultivate botanical species carefully. The varying presence of soil attributes like alkalinity, humus, topsoil, Farm Yard Manure (FYM), organic matter, and Phyto-nutrients is an active area of research. Macro-nutrients and micro-nutrients present in soil overlook the amount of water consumed or produced as part of an agricultural process. Specific standard measures of soil attributes have been considered in past research. Forestation is also necessary to sustain agricultural land by providing rain-fed irrigation while ensuring low soil erosion levels. It is ascertained that a certain amount of the earth’s well-being is linked to crop cycles and agricultural production levels. In this research work, an algorithm called MISTRAL (Soil nutrient enrichment in the Indian Subcontinent with Mathematical Interpretations) is presented, which can be utilized to enrich soil nutrients and soil well-being levels leading to an overall increase in the net agricultural output in the Indian subcontinent.

Soil Erosion Analysis with GIS: A Case Study of Oued Sly Catchment, Northern Algeria

Soil erosion is a process that involves the detachment and transportation of soil particles by water, presenting notable challenges of the depletion of soil fertility, diminished agricultural productivity, and consequences for water reservoirs. The integration of Geographic Information System (GIS) and modeling techniques provides a valuable platform for assessing and addressing soil water erosion. This study specifically examines the risk of soil water erosion in the Oued Sly catchment within the Middle Cheliff watershed in northern Algeria. Employing the Universal Soil Loss Equation (USLE) and thematic maps, the research evaluates the key factors influencing erosion. Results reveal that the catchment generally experiences low to moderate erosion levels, averaging 23.4 to 40 t ha-1 yr-1 across 90.7% of the total area. However, around 9.3% of the catchment exhibits higher erosion rates exceeding 40 t ha-1 yr-1. These findings offer valuable insights for informed watershed management and strategies to mitigate soil water erosion in comparable regions

Estimation of soil loss using RUSLE model and GIS tools: Case study in the Jucusbamba Micro-Watershed (Amazonas, NW Peru)

Human activities have intensified soil erosion globally, negatively impacting the physical, chemical, and microbiological quality of water and soil. This study estimated soil loss in the Jucusbamba Micro-Watershed (Amazonas, northwestern Peru) using the Revised Universal Soil Loss Equation (RUSLE) integrated with Geographic Information Systems (GIS) and remote sensing (RS) data. Meteorological data, soil maps, digital elevation models, and land cover and use maps were integrated into a GIS environment to predict the spatial distribution of erosion. The results showed five classes of soil loss severity: slight (93.34%), moderate (3.94%), high (1.82%), very high (0.61%), and severe (0.29%). Areas with high, very high, and severe erosion levels were mainly located in the middle and lower parts of the micro-watershed. The average annual soil loss was estimated at 23.24 t/ha/year. The information obtained is crucial for the formulation of soil management plans and programs to address erosion problems in the Jucusbamba River Micro-Watershed. Future research should focus on validating these models through field studies and implementing soil conservation practices based on these findings. Keywords: Amazonas, hydrology, RUSLE model, water erosion map, watershed.

The last days of Aporia crataegi (L.) in Britain: Evaluating genomic erosion in an extirpated butterfly.

Current rates of habitat degradation and climate change are causing unprecedented declines in global biodiversity. Studies on vertebrates highlight how conservation genomics can be effective in identifying and managing threatened populations, but it is unclear how vertebrate-derived metrics of genomic erosion translate to invertebrates, with their markedly different population sizes and life histories. The Black-veined White butterfly (Aporia crataegi) was extirpated from Britain in the 1920s. Here, we sequenced historical DNA from 17 specimens collected between 1854 and 1924 to reconstruct demography and compare levels of genomic erosion between extirpated British and extant European mainland populations. We contrast these results using modern samples of the Common Blue butterfly (Polyommatus icarus); a species with relatively stable demographic trends in Great Britain. We provide evidence for bottlenecks in both these species around the period of post-glacial colonization of the British Isles. Our results reveal different demographic histories and Ne for both species, consistent with their fates in Britain, likely driven by differences in life history, ecology and genome size. Despite a difference, by an order of magnitude, in historical effective population sizes (Ne), reduction in genome-wide heterozygosity in A. crataegi was comparable to that in P. icarus. Symptomatic of A. crataegi's disappearance were marked increases in runs-of-homozygosity (RoH), potentially indicative of recent inbreeding, and accumulation of putatively mildly and weakly deleterious variants. Our results provide a rare glimpse of genomic erosion in a regionally extinct insect and support the potential use of genomic erosion metrics in identifying invertebrate populations or species in decline.

Extreme erosion and bulking in a giant submarine gravity flow.

Sediment gravity flows are ubiquitous agents of transport, erosion, and deposition across Earth's surface, including terrestrial debris flows, snow avalanches, and submarine turbidity currents. Sediment gravity flows typically erode material along their path (bulking), which can dramatically increase their size, speed, and run-out distance. Hence, flow bulking is a first-order control on flow evolution and underpins predictive modeling approaches and geohazard assessments. Quantifying bulking in submarine systems is problematic because of their large-scale and inaccessible nature, complex stratigraphy, and poorly understood source areas. Here, we map the deposits and erosive destruction of a giant submarine gravity flow from source to sink. The small initial failure (~1.5 cubic kilometers) entrained over 100 times its starting volume, catastrophically evolving into a giant flow with a total volume of ~162 cubic kilometers and a run-out distance of ~2000 kilometers. Entrainment of mud was the critical fuel, which promoted run-away flow growth and extreme levels of erosion.

Monitoring of River Morphological Change Using Remote Sensing and Hec-Ras in Lusi River, Indonesia

Changes in river flow have become a natural cycle of the river. The Lusi River has problems with meanders due to sediment transport, which is difficult to control. A combination of GIS with RS and HEC-RAS simulation was used to monitor river flow. The water monitoring method utilizes four water indices: NDWI, MNDWI, ANDWI, and SAVI, while the MPM-Toffaleti method is used for simulation. By combining the four methods, accuracy values of 0.68 to 0.92 and precision levels of 0.60 to 0.93 were obtained. MNDWI obtained quite high results compared to other indices. The results showed that the Lusi Riverexperienced quite extreme flow changes. Two flow cuts occurred. Considerable erosion occurred from 2003 to 2013 with a total lost area of 0.1943 km2, while from 2013 to 2023, there was erosion of 0.1177 km2. The HEC-RAS simulation of the Lusi River experienced erosion of 60 to 70.4 percent of the length of the stream. Changes in the riverbed in 2013 were found to be -1.1 ± 2.03 m, and then in 2023, the range of changes in the riverbed was -2.69 ± 1.29 m. Based on the results of the index and simulation of the Lusi River experiencing erosion in the flow, the level of erosion has increased every period.

Responses of soil microbial biomass carbon and microbial entropy to soil properties in typical sloping croplands of China under erosion conditions

Soil microbial biomass carbon (MBC) and microbial entropy play a crucial role in the carbon cycle of terrestrial ecosystems, while their responses to soil properties in typical sloping croplands under the impact of soil erosion remain poorly understood due to the complexity of the soil erosion process. In this study, we selected typical sloping croplands with different erosion levels for the four severely eroded soil types (black, loess, purple, and red soil) in China to assess the key controls of MBC and microbial entropy under the influence of soil erosion. The results showed that soil erosion significantly reduced the MBC content but increased the microbial entropy of sloping croplands in black soil region (BS) (22 %, 43.6 %), purple soil region (PS) (25.5 %, 26.2 %) and red soil region (RS) (28.9 %, 21.9 %), but not in loess soil region (LS). The soil physicochemical properties had significantly positive and negative correlations on the MBC and microbial entropy, respectively. The MBC and microbial entropy of these sloping croplands had different dominant drivers under soil erosion. Overall, our results revealed that changes in MBC and microbial entropy directly depended on the fundamental properties of the soil and soil erosion could indirectly affect the MBC and microbial entropy by directly affecting the physicochemical properties of soil. Thus, the impact of soil erosion on sloping croplands and the associated responses following changes in MBC and microbial entropy provide fresh insights into predicting the effects of soil erosion on carbon stability.

Potential Reduction of Spatiotemporal Patterns of Water and Wind Erosion with Conservation Tillage in Northeast China

Conservational tillage (NT) is widely recognized globally for its efficacy in mitigating soil loss due to wind and water erosion. However, a systematic large-scale estimate of NT’s impact on soil loss reduction in Northeast, China’s primary granary, remains absent. This study aimed to investigate the spatial and temporal variability of soil erosion under NT compared to conventional tillage (CT) in the black soil region and to analyze the underlying mechanisms driving these erosions. The Revised Universal Soil Loss Equation (RUSLE) and the Revised Wind Erosion Equation (RWEQ) models were employed, incorporating previously published plot/watershed data to estimate the potential reduction of water and wind erosion by NT in this region. Results indicated that under CT practices, water- and wind-induced soil losses were widely distributed in the arable land of Northeast China, with intensities of 2603 t km−2 a−1 and 34 t km−2 a−1, respectively. Furthermore, the erosive processes of water and wind erosion were significantly reduced by 56.4% and 91.8%, respectively, under NT practices compared to CT. The highest efficiency in soil conservation using NT was observed in the mountainous regions such as the Changbai Mountains and Greater Khingan Mountains, where water erosion was primarily driven by cropland slopes and wind erosion was driven by the wind speed. Conversely, the largest areas of severe erosion were observed in the Songnen Plain, primarily due to the significant proportion of arable land in this region. In the plain regions, water-induced soil loss was primarily influenced by precipitation, with light and higher levels of erosion occurring more frequently on long gentle slopes (0–3°) than on higher slope areas (3–5°). In the temporal dimension, soil loss induced by water and wind erosion ceased during the winter under both tillage systems due to snow cover and water freezing in the soil combined with the extremely cold climate. Substantial reductions were observed under NT from spring to autumn compared to CT. Ultimately, the temporal and spatial variations of soil loss under CT and NT practices were established from 2010 to 2018 and then projected onto a cropland map of Northeast China. Based on this analysis, NT is recommended as most suitable practice in the southern regions of Northeast China for maintaining soil health and crop yield production, while its suitability decreases in the northern and eastern regions.

Numerical investigation of flow around the injector of a Pelton turbine due to eroded needle

Abstract Injectors of Pelton turbines are prone to both sediment erosion and cavitation. This causes degradation of the surface morphology, which aggravates the quality of the jet, lowering the turbine’s performance. The study focuses on CFD analysis of a groove-shaped erosion pattern on the needle and analyses its influence on the quality of the jet at the three stages of erosion. The numerical model comprises of a nozzle with a cylindrical passage for modelling the jet. The research used the SST turbulence model and boundary conditions defined according to the turbine’s data, from which the model was obtained. This study explores the impact of silt erosion on pressure signals around the injector of a Pelton turbine. Needle pressure distribution curves were plotted at various erosion levels and openings, revealing that pressure deviation increases with increase in erosion. The effect turns out to be minimal during high opening levels but becomes substantial as opening levels decrease. Operating in part load conditions leads to a significant pressure drop due to the reduction in flow rate. The pressure distribution tends to become more uniform at full load, achieving optimal flow rates. However, a noticeable pressure drop is observed in the eroded region, reaching a minimum at the deepest eroded area. The pressure drop is further amplified with an increase in the level of erosion, indicating erosion’s disruptive impact on fluid flow. The findings highlight the complex interplay between erosion, needle pressure distribution, and jet diffusion.

Spatial assessment of soil resources on different land uses and slope gradient as a planning tool, in Ferenjua watershed, Ethiopia

Soil erosion, land degradation and climate change are the major environmental threats attributed to low agricultural productivity in Ethiopia. To reduce soil erosion and restore degraded lands, integrated soil and water conservation interventions have been implemented. However, the impacts of the intervention measures were not sufficiently studied due to the lack of baseline information. Therefore, this study was carried out to evaluate and understand the current conditions of biophysical resources in Ferenjua watershed, which is located in Gondar zuria district. In this study, more emphasis was given to the levels of total nitrogen (TN), available phosphorous (P), organic matter (OM), bulk density (BD), pH, moisture, texture and soil erosion. To collect the biophysical data, the watershed was divided into 144 grid-based sampling points with a resolution of 250 m by 250 m. In addition, the data were collected in 8 representative profile pits. Three primary land uses were identified from supervised land use and land cover classification and described as cultivated land (55.08 %), forestland (30.80 %), and grassland (14.12 %). Erosion hotspot map shows that >40 % of the watershed is moderately and highly susceptible to soil erosion. The highest BD (1.36 gm cm−3) was observed at Vertisols-dominated cultivated lands located in the flatlands, whereas, the lowest BD (1.28 gm cm−3) was observed under forestland. Regarding the results of TN, P, and OM, >60 % of the watershed was classified as having low to very low soil nutrient levels. Consequently, development interventions should be considered to restore degraded lands for the sustained use of resources in the watershed.

Penilaian Tingkat Kekeritisan Lahan Pertambangan dan Beberapa Pengguanaan Lahan Lainnya di Kalimantan Selatan

Critical land is land that is no longer productive from an agricultural perspective, because management and use do not consider land management requirements and soil conservation principles. This research aims to assess the level of criticality of land based on the level of erosion that occurs at various coal mining land locations in several districts in South Kalimantan. This research is non-experimental research using exploratory descriptive methods. The data collected is secondary data obtained through official publications from the Environmental Service and related agencies from several environmental documents of coal mining companies that have received approval from the authorized Agency. The secondary data used is the data needed to calculate the amount of erosion which is used as a basis for evaluating land criticality. These data include: soil texture, permeability, bulk density, rainfall, slope and slope length, management factors, land cover vegetation factors and soil organic C. Erosion estimation uses the Universal Soil Loss Equation (USLE) method. The results of erosion calculations using USLE show that in open mine land in Banjar Regency it is 233.9 tons ha-1 year-1, while in Tanah Laut Regency is 173.1 tons ha-1 year-1 and in Kotabaru Regency is 275.1 tons ha-1 year-1. The level of criticality of land in the mining area is at a critical and very critical level compared to natural land and cultivated land due to differences in erosion values ​​and also the thickness of the soil solum studied.

Araguainha impact structure, Brazil: New insights into the geology of the central uplift

AbstractExtensive, new outcrops along the MT‐100 state road in the northern part of the central uplift of the 40‐km diameter, 252–259 Ma old Araguainha impact structure, Central Brazil, have become available for investigation. They offer new insight into the contact relationships between the different lithologies and the genesis of different types of impact‐related rocks, as well as the current level of erosion of the structure. Three types of impact melt rock (IMR) with different field relationships and compositions can now be distinguished: (1) Type‐I of granitic composition and occurring mainly as veins and dikes, besides a few larger pods, in the central alkali granite core of the central uplift; (2) Type‐II in the form of plastically deformed clasts of mainly highly silicious compositions in polymict impact breccia; and (3) Type‐III, derived from partially melted conglomerate or sandstone precursors, and that occurs at selected sites in (meta)sedimentary strata of the basement in the immediate environs of the alkali granite core. Both polymict lithic and melt‐bearing (suevitic) impact breccias are recognized in the 110‐m thick integrated section through impact breccia directly overlying the crater floor. This crater floor is composed of (meta)‐sedimentary basement strata with granite injections and, locally, sandstones of the Devonian sedimentary Furnas Formation of the Paraná Basin. Main breccia components are (meta)‐pelites and (meta)sandstones of the basement that is currently favored to be related to the regional Paraguay Belt and to the lower sequence of the Paraná Basin sedimentary strata. Locally, breccia contains clasts of IMR Type‐II, and only very rarely are granitic fragments observed. Clasts of IMR Type‐I have never been observed in the breccia deposits. These new observations preclude significant involvement of alkali granite in the formation of the polymict breccia or in the production of shock melts. They also reveal the major role of the (meta)sedimentary precursors in the production of IMR by shock melting and provide essential information for better understanding the cratering processes involved in the formation of an impact structure in a sedimentary target, of the size of the Araguainha impact structure.

The Estimation of the Amount of Water Erosion at Qalachwalan Basin by Gavrivolic Model

Qalachwalan basin is important agricultural and it is one of the main water resources for Slemani city. The basin contains useful natural resources that are conducive to agricultural development. As the area is a hill country, Gavrilovic model was chosen to get the size and amount of water erosion to determine the erosion risks that the basin is facing. This research was conducted based on Gavrilovic (EPM) model using (RS & GIS) to determine the level, amount, and size of water erosion of Qalachwalan basin. We found out that, through the research, the slopes that are in the direction of the estuaries face water erosion much more due to the form of the basin in its creation, which has many slopes and little vegetation on the cliffs that are a main cause of the speedy runoff. Also, poor planning to confront or reduce the risks of flood which increases the erosions. The erosion estimated based on Gavrilovic model between very weak erosion at less than (100 m3/km2/year) and very strong erosion at (5000 – 20000 m3/km2/year). The basin generally lies in the circle of moderate water erosion at (1230 m3/km2/year). Therefore, for the secondary basins (e.g. Jogasur, Mawakan, and estuary) the erosion based on Gavrilovic model was high consecutively in this way (1720, 2584 and 4356 m3/km2/year). Our results very impotent for local government stockholders to establishment new dams in cliffs areas for agriculture and determine life cycle of these dams in this areas, and find new solution to reduce soil erosions in near future.

Spatio-Temporal Variations in Soil Erosion and Its Driving Forces in the Loess Plateau from 2000 to 2050 Based on the RUSLE Model

Assessing the spatio-temporal variability and driving forces of soil erosion on the Loess Plateau is critical for ecological and environmental management. In this paper, the Revised Universal Soil Loss Equation (RUSLE) model, the patch-generating land use simulation, and the Geographical Detector are used to investigate the spatio-temporal variations of the Loess Plateau’s soil erosion from 2000 to 2050. The results showed that: (1) The primary categories of soil erosion from 2000 to 2020 were moderate, mild, and slight, and the average level of soil erosion exhibited a decreasing and then an increasing tendency during the last 20 years. (2) Soil erosion was directly impacted by changes in land use, with cropland and forest being the primary land use and land cover changes in the study region. Cropland and construction land being turned into woodland between 2000 and 2020 resulted in a significant decrease in the severity of soil erosion. Projected soil erosion is expected to increase significantly between 2020 and 2050 due to arable land being converted into construction land. (3) The key variables impacting the spatial distribution of soil erosion were LUCC (Land-Use and Land-Cover Change), NDVI (Normalized Difference Vegetation Index), and slope, and the interplay of these variables may increase their ability to explain soil erosion. Grasslands with an NDVI ranging from 0.9 to 1, rain ranging from 0.805 to 0.854 m, a slope above 35°, and a terrain elevation ranging from 1595 to 2559 m were identified as having a high risk of soil erosion. Soil erosion prevention and management efforts should focus on the ecological restoration of upland areas in the future.

Investigation of the flood event under global climate change with different analysis methods for both historical and future periods

ABSTRACT Global climate change is a phenomenon resulting from the complex interaction of human influences and natural factors. These changes lead to imbalances in climate systems as human activities such as greenhouse gas emissions increase atmospheric gas concentrations. This situation affects the frequency and intensity of climate events worldwide, with floods being one of them. Floods manifest as water inundations due to factors such as changes in rainfall patterns, rising temperatures, erosion, and sea level rise. These floods cause significant damage to sensitive areas such as residential areas, agricultural lands, river valleys, and coastal regions, adversely impacting people's lives, economies, and environments. Therefore, flood risk has been investigated in decision-making processes in the Diyarbakır province using the Analytical Hierarchy Process (AHP) method and future disintegration of global climate model data. HadGEM-ES, GFDL-ESM2M, and MPI-ESM-MR models with RCP4.5 and RCP8.5 scenarios were used. Model data were disintegrated using the equivalent quantile matching method. The study reveals flood risk findings in the HadGEM-ES model while no flood risk was found in the GFDL-ESM2M and MPI-ESM-MR models. In the AHP method, flood risk analysis was conducted based on historical data across Diyarbakır and interpreted alongside future rainfall data.

Assessing the level of river basin evolution, erosion susceptibility and its correlation with morphometric characteristics using Geoinformatics techniques

The application of Geoinformatics have become fastest and improved advanced tools to analyse and interpret the topography and hydrological characteristics. This study aimed to utilize the advantage of high resolution (30 m) remote sensing data of Shuttle Radar Topography Mission (SRTM) and the geoinformatic tools of Quantum Geographical Information System (QGIS) for extraction of detailed and accurate drainage morphometry and elevation information in preparation of hypsometric curves. Making use of QGIS, the SRTM data and topographic maps are georeferenced and pre-processed algorithm tools of stream burning and fill-DEM are applied for DEM preparation and extraction of accurate drainage network and its basin areas. From the DEM map, the details of elevation and area of basins are extracted for preparation of hypsometric curves. Hypsometric curves are analyzed to interpret and understand the heterogeneity in the levels of basin evolution/development and erosion at 4th order sub-basin level. The concave hypsometric curves of main basin and sub-basins indicate that total basin as well as sub-basins reached the old/monadnock stage due to the dominance of fluvial process. Based on the hypsometric area/integral (Ea) and Concavity of hypsometric curve values (Eh), five classes/stages of basin development and erosion levels are identified within the old/monadnock stage. The Ea values range from 0.10 to 0.35 and Eh range from 0.25 to 0.77 in this study area. Initial old/monadnock stage of basins have Ea values > 0.28 and Eh values < 0.4 indicating low levels of erosion among the sub-basins. Low hypsometric area/integral value (Ea) indicates the higher level of landmass removal by erosion and basin development. The oldest stage basins are identified with Ea values range from 0.10 to 0.15 and Eh values range from 0.61 to 0.77 indicating higher level of landmass removal/erosion. The lithological variation plays a significant role on hypsometry of the basins. The high hypsometric integral (Ea) values (i.e., 0.28 to 0.35) of 1,2 and 3 sub-basins indicating the early/ initial level of old stage in its’ basin development, since the resistant basalt formation is sandwiched between sandstones prevented deep erosion and depicting less dissected topography. The hypsometric integral has positive correlation with form factor and negative correlation with drainage morphometric characteristics. It indicates that the level of basin evolution increases as the form factor decreases but number of streams, length of streams, mean bifurcation ratio, relief, relief ratio and ruggedness ratio increases. This study is highly useful to understand the relation among morphometric characteristics, basin development and erosion levels through the analysis of hypsometric curves making use of Geoinformatic techniques.

Health status and characterisation of Gibraltar’s maerl beds

Maerl beds form heterogeneous, three-dimensional habitats for numerous species, housing high levels of biodiversity and species richness across the globe. Despite the importance of maerl’s ecological and carbon-regulating role; there is still a lack of information on methods to characterise its health. Therefore, this research set out to develop a standardised health assessment framework to assess the overall health of maerl a) structural function and b) habitat function. The framework was tested in an area of Gibraltar that has historically been severely impacted from various pressures including water quality. The maerl health is in a critical status, as over 92 % of it is deemed dead, with high levels of surface erosion and unusual colourations observed, and rhodoliths were generally small in size (mean: 1.35 cm ± 0.19 cm). The habitat health was labelled as intermediate, based on the species richness values, signs of nursery function, high number of Terebellidae (n = 233), distribution and coverage, and type of sediment composition. The maerl-forming species morphologically identified as Lithophyllum cf. racemus and Lithothamnion cf. corallioides were found to be present in the study site, which are first records within Gibraltar’s waters.