Geomorphological Features Research Articles

Hydrogeochemical processes as a conditioner of freshwater lenses associated with coastal deposits

AbstractThe aim of this work was to study the processes and factors conditioning the hydrochemistry of freshwater lenses associated with Holocene coastal deposits in an area of the Argentinean Atlantic coast. For this purpose, geomorphological units were mapped and a shallow groundwater monitoring network was established, including pre‐existing boreholes and shallow exploration wells. During the construction of the shallow exploration wells, sediment samples were extracted to determine the texture and mineralogical characteristics. Four samplings were carried out to measure in situ physicochemical parameters and to determine majority ions in the water. The chemical data were analysed considering the associated geomorphology, lithology, water balance and hydrodynamics. The geomorphological and lithological characteristics are the combined factors that favour the preferential rainwater recharge processes. Geoforms with greater topography and extension (continental and coastal dunes) tend to store freshwater lenses, while those with lower topography and little areal extension (sand sheets and beach ridges) have very thin lenses and tend to become salinized. Climate and local water balance are factor that determines that groundwater recharge occurs preferentially in winter. This causes increases in groundwater levels and a decrease in the groundwater EC. On the other hand, mineralogy is a factor that conditions the geochemical processes associated with the water–sediment interaction. Within the main geochemical processes, the dissolution and/or mineral weathering, the dissolution of CO2(g) and ion exchange determine the presence of different hydrochemical facies, where Ca‐HCO3 facies dominates in elevated geoforms, while Na‐Cl in lower ones. The results obtained in this work have provided an understanding of the factors and processes that condition groundwater chemistry in coastal deposits, being of vital importance for the management of water resources.

Some Geomorphological Implications of Chemical Weathering in Sequences of Sedimentary Rocks in the Kirkuk Structure

This study was based on a review of a group of geomorphological features and characteristics within the Kirkuk anticline in the Low Folded Zone within the Unstable Shelf of Iraq. As well as identifying the role of the chemistry of the rocks that form the geological formations in the studied area and explaining the role of chemical weathering processes in shaping the geomorphological units. Each of these geomorphological units includes several landforms with different lithologies. These shapes were produced as a result of weathering, erosion, and sedimentation processes associated with structural, compositional, rock, and climatic factors. Literature. The exposed rocks in the sedimentation basin, from which different formations are formed, showed variation in their resistance to chemical and physical weathering processes. It has been noted that the chemical weathering of gypsum rocks is of the type of incipient weathering and that of limestone is of the type of incipient to moderate weathering. For the sandstones, they are of the moderate weathering type, while it is noted that the chemical weathering of the claystone and marl is of the extreme weathering type. This demonstrates the important role played by the type of rocks and their chemical composition in highlighting the role of various geomorphological processes in determining the nature of land units and forming the geomorphological features, in addition to the influence of various geological processes and the presence of structural units such as joints, fractures, and faults, as well as the influence of slope and various climatic factors.

Оценка уязвимости карстовых подземных вод к загрязнению на основных массивах Горного Крыма с использованием региональной методики

Introduction. Assessment of groundwater vulnerability to contamination is an effective tool for scientific substantiation of the sanitary protection zones for drinking water sources. Karst ground waters of the Mountain Crimea form the main resources for water supply in the Crimean Peninsula. This study has a purpose to perform the assessme nt and mapping of karst ground waters resource vulnerability to contamination on such representative massifs of the Crimean Mountains as Chatyrdag, Dolgorukovsky, Karabi and Ay-Petri . Materials and methods. Assessment of karst ground waters vulnerability is conducted by use of Mountain -Crimean method. It has been developed on the base of some wide-tested European methods (COP-method and Slovene approach) with methodological modification and adaptation to regional conditions of the Mountain Crimea. The input data for assessment is spatial information about ground waters vulnerability factors: protective layers in vadose zone, flow concentration by streams, sinkholes and caves, precipitation regime etc. The collected spatial information was converted into attributed geo data layers, which were subsequently subjected to overlay operations in Arc GIS 10 software according to assessment scheme. Results. According to the assessment results, approximately 34 and 14% of the Chatyrdag massif area gained the category of high and very high vulnerability, on the Karabi massif – 14 and 17%, on the Dolgorukovsky massif – 14 and 2%, on the Ay-Petri massif – 19 and 7% of total area respectively. The result ing vulnerability maps demonstrate significant mosaics and contrast, which is associated with discrete distribution of protective covers and high differentiation of ground water recharge conditions within the catchments of karst massifs. Discussion. Analysis of the resulting vulnerability maps have revealed that the leading factors determining areas of high and very high vulner ability of karst waters are runoff concentration factors, while the factors of protective cover mainly determine the areas with low vulnerability. The zones of high vulnerability on the Chatyrdag and Karabi massifs are mainly coincide with areas of high density of karst forms (sinkholes and caves), while high vulnerability zones of the Ay-Petri and Dolgorukovsky massifs are predominantly associated with areas near permanent and temporary watercourses. In general, the obtained maps of groundwater vulnerability are quite consistent with the known data on the hydro-geological conditions of the assessed massifs. Conclusions. The identified differences in the area ratio and spatial distribution of ground waters vulnerability categories between the assessed massifs are a consequence of local geological, geo-morphological and hydrological features. The obtained results confirm high applicability of the Mountain-Crimean regional method for groundwater vulnerability assessment, at least for the karst massifs of the Mountain Crimea. Suggestions for practical application and direction for future research. The produced groundwater vulnerability maps create a scientific basis for delineation of water protection zones, assessing the risks of groundwater pollution and developing the territorial planning schemes within studied areas. The next stage of study is an assessment of groundwater source vulnerability for individual karst springs used in water supply.

THE ROLE OF GEOLOGICAL RELATIONSHIP AND BRAND OF GEOPRODUCT ON REGIONAL DEVELOPMENT IN SAMOSIR ISLAND OF GEOPARK CALDERA TOBA WITH MEDIATING METHOD

Geoproducts have a specific philosophy, a geological relationship that visible and understandable through the utilization of geological and geomorphological features from diversity of geological, biological and cultural heritage then strengthened by geo-brand as added value of the product. As local products of certain region, geoproducts as an unique tourism product, through membership of Geopark Global Network (GGN), play role identifying the geopark itself and become market tools where geo-brands can take it. Samosir Island, as part of Toba Caldera Geopark, is the world's greatest Caldera with outstanding potential, became member of GGN in year of 2020. Data processing in this study used smartPLS SEM (Partial Least Square - Structural Equation Modeling) software.Various tourism products as geoproducts activity grow, whereas geoproducts are expected to follow the philosophy then becoming sector in development region of geopark, yet have no geo-brand. The geological relationships significantly impact the rise of tourism activities in the regional development of Toba Caldera. This is achieved by incorporating the products' geological, biological, and cultural factors. Usin g geological features must catch up to its potential as a world heritage site. Therefore, it is crucial to maintain these highly delicate elements through geotourism. A study was conducted on geoproduct actors from the supply side of tourism to see how the geological relationship is related to various products that can provide regional development in principle of sustainability a nd how geoproduct actors comprehend geo-brand on their products as an identity of worldwide product.

Organic carbon accumulation in British saltmarshes

Saltmarshes are a crucial component of the coastal carbon (C) system and provide a natural climate regulation service through the accumulation and long-term storage of organic carbon (OC) in their soils. These coastal ecosystems are under growing pressure from a changing climate and increasing anthropogenic disturbance. To manage and protect these ecosystems for C and to allow their inclusion in emissions and natural-capital accounting, as well as carbon markets, accurate and reliable estimates of OC accumulation are required. However, globally, such data are rare or of varying quality. Here, we quantify sedimentation rates and OC densities for 21 saltmarshes in Great Britain (GB). We estimate that, on average, saltmarshes accumulate OC at a rate of 110.88 ± 43.12 g C m−2 yr−1. This is considerably less than widely applied global saltmarsh averages. It is therefore highly likely that the contribution of northern European saltmarshes to global saltmarsh OC accumulation has been significantly overestimated. Taking account of the climatic, geomorphological, oceanographic, and ecological characteristics of all GB saltmarshes and the areal extent of different saltmarsh zones, we estimate that the 451.65 km2 of GB saltmarsh accumulates 46,563 ± 4353 t of OC annually. These low OC accumulation rates underline the importance of the 5.20 ± 0.65 million tonnes of OC already stored in these vulnerable coastal ecosystems. Going forward the protection and preservation of the existing stores of OC in GB saltmarshes must be a priority for the UK as this will provide climate benefits through avoided emissions several times more significant than the annual accumulation of OC in these ecosystems.

The power of nature (sports)? From anthropocentrism to ecocentrism

ABSTRACT Nature sports include pursuits such as paragliding, white-water kayaking, free diving, mountaineering, and surfing. Participants in nature sports interact with geographical features (e.g. mountains, rivers, oceans, snow fields, ice sheets, caves, rock faces) as well as the dynamic forces that produce them (e.g. gravity, waves, thermal currents, flowing water, wind, rain, sun). In this article, I engage a representational approach to analyze how participants in nature sports interact with nature. Anthropocentric representations privilege participants’ interests, wants, desires, and ends; they typically refer to claims of conquest/achievement in nature, or praise nature for its therapeutic qualities. In contradistinction, ecocentric representations recognize humankind as one entity in an interdependent world that comprises all living organisms and the geological processes and geomorphological features that sustain them. Ecocentric representations of nature sports highlight networks of participants and landforms that help preserve a balance between people and the environment. Yet, notwithstanding the allure of ecocentric representations, especially in the wake of evidence that human-induced greenhouse gases are predisposing environmental calamities, there is a substantial gap between the ontological concepts and categories of ecocentrism and lived sporting experiences and practices in nature.

Automatic extraction of multiple morphological parameters of lunar impact craters

AbstractImpact craters are geomorphological features widely distributed on the lunar surface. Their morphological parameters are crucial for studying the reasons for their formation, the thickness of the lunar regolith at the impact site and the age of the impact crater. However, current research on the extraction of multiple morphological parameters from a large number of impact craters within extensive geographical regions faces several challenges, including issues related to coordinate offsets in heterogeneous data, insufficient interpretation of impact crater profile morphology and incomplete extraction of morphological parameters. To address the aforementioned challenges, this paper proposes an automatic extraction method of morphological parameters based on the digital elevation model (DEM) and impact crater database. It involves the correction of heterogeneous data coordinate offset, simulation of impact crater profile morphology and various impact crater morphological parameter automatic extraction. And the method is designed to handle large numbers of impact craters in a wide range of areas. This makes it particularly useful for studies involving regional‐scale impact crater analysis. Experiments were carried out in geological units of different ages and we analysed the accuracy of this method. The analysis results show that: first, the proposed method has a relatively effective impact crater centre position offset correction. Second, the impact crater profile shape fitting result is relatively accurate. The R‐squared value (R2) is distributed from 0.97 to 1, and the mean absolute percentage error (MAPE) is between 0.032% and 0.568%, which reflects high goodness of fit. Finally, the eight morphological parameters automatically extracted using this method, such as depth, depth–diameter ratio, and internal and external slope, are basically consistent with those extracted manually. By comparing the proposed method with a similar approach, the results demonstrate that it is effective and can provide data support for relevant lunar surface research.

Evaluation of sediment budgets in catchments prone to flash flood-related debris flows: A case study from the southern Apennines (Italy)

The evaluation of sediment budgets of flash-flood prone torrential catchments is important for the assessment of flood susceptibility and hazard in piedmont areas. Here, we developed and tested a predictive, quantitative geomorphological technique for estimating the magnitude of debris flows related to flash floods triggered by extreme rainfall events. We applied our method to steep torrential catchments that allowed testing of our technique through quantification of the effects of recently-occurred flash floods. The three study catchments are located in southern Italy and experienced flash flood-related debris flows triggered by a rainstorm with a recurrence interval > 200 yrs. The study basins are small size, steep, narrow and the stream network has a low order (maximum 3rd order). We estimated the volumes of loose sediment stored in the bottoms of the mainstem valleys of the investigated mountainous catchments prior to the flash flood and compared our results with the sediment volumes entrained by the debris flows. The latter volumes were estimated by post-event data collected by means of field surveys. The results were mutually consistent so supporting our approach. The approach is fit to the analysis of torrential catchments with geomorphological features comparable to those of our study basins, provided (i) the stream is confined by hard rock slopes not affected by channel lateral erosion, (ii) all stored sediment is eroded and transported downstream during the flood, and (iii) no landslide occurs along the hillslopes. For these types of ungauged catchments, our method can be applied extensively, even in the absence of field data and measurements, for flash flood hazard assessment and planning of mitigation strategies.

Sentinel-2 MSI image time series reveal hydrological and geomorphological control of the sedimentation processes in an Amazonian hydropower dam

Monitoring sediment transport in a run-of-river hydropower dam was investigated to detect and quantify the siltation processes using Sentinel-2/MSI satellite images. We developed a method allowing us to assess the fate of sediment discharge in reservoirs and to map the locations of eroding and silting stream cross sections. This monitoring was achieved by retrieving the seasonal and interannual variation in suspended sediment concentration (SPM) longitudinally and by developing indices to detect local deviations from the overall SPM trend. A comparison between Sentinel-2 reflectance, processed for atmospheric and glint correction, and field measurements showed fine accuracy for the b8a/b4 band ratio (RMSE = 0.23 sr-1, N = 50) as well as a very good SPM retrieval performance for a wide range of concentrations [10–926 mg/L] with an RMSLE of 0.23 mg/L. SPM trend analysis demonstrated that significant (p < 0.001) sedimentation processes (i.e., decreases in SPM concentration upstream to downstream) occur for most parts of the hydrological cycle except during peak flooding when there was no significant SPM siltation. The overall rate of SPM decrease is −0.52 mg/L/km, varying from +0.11 mg/L/km down to −1.10 mg/L/km. We developed a deviation index to detect local anomalies from the overall upstream–downstream satellite-derived SPM trend. A satellite-derived map of eroding and silting reaches is produced evidencing the control of the sediment transport pattern by geomorphological features, such as rapids. Using independent bathymetric surveys, we showed that satellite data allow the locations of eroding and silting river reaches to be correctly mapped.

Littoral landforms of Lake Hulun and Lake Buir (China and Mongolia): Wind-driven hydro-sedimentary dynamics and resulting clastics distribution

Two rectangular-shaped lakes, Lake Hulun and Lake Buir, located at the boundary between China and Mongolia, only c. 75 km apart and therefore experiencing similar wind fields, have been studied based on satellite images and field surveys in order to compare their geomorphological and sedimentological characteristics. The wind-driven hydrodynamics, which have a significant effect on the development of littoral landforms and on sediment distribution, have been discussed for the two similar lakes that experienced a prevailing wind perpendicular to their long axis. A conceptual model related to wind-driven water bodies and sediment distribution is proposed. Wave-influenced to wave-dominated deltas, beaches, spits, and eolian dune deposits develop around these two lakes, with a strikingly similar distribution pattern. These features locally inform the longshore drift and help reconstruct the water circulation induced by wind forcing. Under the NW prevailing wind regime, the spits developed on the SW coast with a NW–SE extension, which was influenced by the NW–SE longshore currents. The same influence was observed in the delta extension in the NE area. The differences lie in the presence of fan deltas in the NW region of Lake Hulun, but not in Lake Buir. Additionally, the width of the beach and eolian deposits on the downwind coast of Lake Hulun is three times greater than that of Lake Buir which were caused by the differences in sediment supply and wind fetch between the two lakes. Lake Hulun and Lake Buir provide two reliable examples to understand the relationship among the wind field, provenance, hydrodynamics, landforms, and asymmetrical distribution of clastics in elongated lakes. They also represent relevant modern analogs, which may also be of guiding significance to wind-driven sand body prediction in lacustrine basins.

An Overview of Geomorphological Mapping: A Case Study of Rimbi Chhu River Basin, Sikkim, India

Geomorphology is the primary science which demonstrates the basic understanding and mapping of terrain features. A geomorphological map consists of scientific data and dynamic source of information on characteristics of landforms, their origin and evolution, which can be recorded in a map form. Basin hydrology also gets impacted by the terrain features of a basin as overland flow, stream flow and through flow is largely determined by the underneath surface. The configuration of the basin topography reflects the nature of the interaction between process and form. Profound understanding and in depth analysis of geomorphological features of a river basin can provide beneficial information for predicting, preventing and mitigating natural hazards; managing natural resources sustainably for future generation. Implementation of remote sensing and GIS techniques have fostered incredible improvements in landform recognition and accelerated the growth of geomorphological research. The river Rimbi Chhu has been selected as the study area in order to determine terrain configuration in relation with geomorphological features of the basin area. Visual representation of terrain (such as aspect, slope, channel networks, different river profiles, shaded relief and flow direction) and geomorphological (saddle, ridge line, convex-concave slope, rounded hills, fault for instance) derivatives is therefore illustrated, as well as a description of the challenges and crisis that can occur in this context.

Geomorphologic and infilling characteristics of the shelf-incising submarine canyon in the eastern Makran accretionary prism, offshore Pakistan

Seven shelf-incising submarine canyon systems are developed in the Makran accretionary prism, offshore Pakistan. This paper uses multibeam bathymetric data and multichannel seismic profiles to study the geomorphologic and infilling characteristics of E Canyon in the east of accretionary prism. The E Canyon extends nearly north–south from the upper slope to lower slope, the bottom of the canyon is located in 1000 to 3000 m water depth, the main axis extends about 55 km, and the width varies from 5 to 9 km. The E Canyon shows U-shaped concave features in the northern cross-section view and V-shaped concave features in the southern cross-section view. Two continuous erosion pools are developed at the fifth and third ridges of the southern segment, respectively. The steepest sidewall (with slopes of 25.75° and 40.47°) of E Canyon was found near the third ridge. The filling sequence of coarse channel lags, slump debris flows, stacked channel sands and mass transported deposits and turbidite deposits from bottom to top is developed in the northern segment of the canyon. Strong erosion is developed in the southern part of the canyon and there is no sedimentation inside. On the abyssal plain, the continuation of the E Canyon is clearly erosive. Our preliminary analysis shows that the factors controlling the evolution of E Canyon may include sediment gravity flow, tectonic activity, sea-level change, climate and onshore rivers activity. The correlation between evolution of E Canyon and gas hydrates was explored, and it is believed that the erosion of E Canyon plays a destructive role in hydrate accumulation. At the same time, the destruction of hydrate-bearing layer induces the escape and leakage of hydrocarbon-bearing fluid, leading to the development of pockmark on the sidewalls of E Canyon. And the evolution model of gas hydrate accumulation in the development area of E Canyon was established.

Explanation of the influence of geomorphometric variables on the landform classification based on selected areas in Poland

In recent years, automatic image classification methods have significantly progressed, notably black box algorithms such as machine learning and deep learning. Unfortunately, such efforts only focused on improving performance, rather than attempting to explain and interpret how classification models actually operate. This article compares three state-of-the-art algorithms incorporating random forests, gradient boosting and convolutional neural networks for geomorphological mapping. It also attempts to explain how the most effective classifier makes decisions by evaluating which of the geomorphometric variables are most important for automatic mapping and how they affect the classification results using one of the explainable artificial intelligence techniques, namely accumulated local effects (ALE). This method allows us to understand the relationship between predictors and the model’s outcome. For these purposes, eight sheets of the digital geomorphological map of Poland on the scale of 1:100,000 were used as the reference material. The classification results were validated using the holdout method and cross-validation for individual sheets representing different morphogenetic zones. The terrain elevation entropy, absolute elevation, aggregated median elevation and standard deviation of elevation had the greatest impact on the classification results among the 15 geomorphometric variables considered. The ALE analysis was conducted for the XGBoost classifier, which achieved the highest accuracy of 92.8%, ahead of Random Forests at 84% and LightGBM at 73.7% and U-Net at 59.8%. We conclude that automatic classification can support geomorphological mapping only if the geomorphological characteristics in the predicted area are similar to those in the training dataset. The ALE plots allow us to analyze the relationship between geomorphometric variables and landform membership, which helps clarify their role in the classification process.

Geomorphology of Pramuka Cay, Kepulauan Seribu Regency, Jakarta, Indonesia

Small islands have unique characteristics that make them highly vulnerable to environmental damage and disasters. A good understanding of geomorphological characteristics will greatly assist in understanding the potential damage to natural resources that may occur, as well as help in planning better environmental management and assist in more effective disaster mitigation in the future. This study aims to analyze geomorphological characteristics and identify their influence on potential environmental damage and existing geomorphological hazards. The analysis shows that the geomorphological characteristics of Pramuka Cay cause it to have potential environmental damage and geomorphological hazards consisting of high vulnerability to sea level rise, water resource scarcity, seawater intrusion, groundwater pollution, coastal erosion and tsunami.

Validation of four optimization evolutionary algorithms combined with artificial neural network (ANN) for landslide susceptibility mapping: A case study of Gilan, Iran

Landslides, the most significant geohazards in Iran, adversely affect the region's socioeconomic conditions and the environment. Landslide susceptibility mapping is crucial for proactive risk management, sustainable development, and protecting human lives, infrastructure, and the environment. It enables decision-makers to make informed choices, implement appropriate mitigation measures, and plan for potential landslide events, leading to safer and more resilient communities. Using a recommended subdivision methodology, this research has developed a landslide susceptibility map for a significant Gilan, Iran region. The production of the map involved utilizing an artificial neural network (ANN) model. This model incorporated sixteen causal components from several characteristics, including topographic and geomorphologic features, geological factors, land use patterns, hydrological aspects, and hydrogeological properties. Three hundred seventy instances were identified using multiple verified sources and analyzing aerial photographs to create the landslide inventory map. Examining and verifying the weights assigned to the causal elements were conducted per accepted mathematical standards, incorporating sensitivity analysis, earlier research, and empirical data on landslides. The area under the receiver operating characteristic curve (AUROC) was used to compare the various models. The study's findings indicated that the best swarm size value for COA-MLP11Cuckoo Optimization Algorithm (COA). is equal to 450, and the accuracy indices for this algorithm were 0.998 and 0.995 in training and testing datasets, respectively. Similarly, the AUC22Area under the curve (AUC). for the HS-MLP,33Harmony Search Algorithm (HS). SFS-MLP,44Stochastic Fractal Search (SFS). and TLBO-MLP55Teaching- Learning-Based Optiization (TLBO). were 0.997, 0.999, and 0.999 in training and 0.995, 0.996, and 0.995 in the testing dataset, respectively. Therefore, the use of optimization algorithms leads to an increase in the performance and accuracy of the neural network, and the high accuracy of the SFS-MLP model demonstrates the existence of a dependable criterion for delineating the susceptibility zones about forthcoming landslide occurrences. The model is a cost-effective and potentially indispensable tool for urban planners in growing cities and municipalities. Its effectiveness is demonstrated by comparisons with previous susceptibility analyses conducted in the region.

Assessment of cyclone induced flood using microwave Synthetic Aperture Radar (SAR) data in four blocks of East Midnapore district, India

East Midnapore district is one of the flood prone regions of West Bengal, India. Geomorphological character, topographic nature and geographical location are the main causes of such kind of flood extensiveness in this region. Four most flood prone blocks of East Midnapore district are considered in this study to analyse, monitor and estimate the flood consequences. Flood intensity, duration of water logging, frequency, interval of flood and measurement of the vulnerability are the important parameters to assess the flood risk. Synthetic Aperture Radar (SAR) data has its distinct character to collect the data at the flood time even in bad weather and it can also penetrate the cloud cover and can avoid weather caused signal attenuation. European Space Agency’s (ESA) Sentinel-1 SAR before and after flood data (2021) of Vertical transmit and Vertical receives (VV) polarization has been used to monitor and detect the flood extension and assess the inundated areas. The decibel (dB) value is mentioned and speckle noise correction is applied before and after both images. By applying the threshold dB values on both images, the flood inundated areas are detected and extracted from the natural water bodies. A village wise water logged condition of this region was observed for a long time and the study reveals that total 11612.28 ha. areas are submerged due to flood inundation. For the development of the agriculture and aquaculture in terms of the local economy a special care should be taken in this low land flood, affected region.

Flash flood prediction in Southwest Saudi Arabia using GIS technique and surface water models

A flash flood is one of the hazardous phenomena, especially in dry regions. In Saudi Arabia, Jazan Province experiences data scarcity especially historical hydrological data and a lack of studies related to flash flood analysis and the rainfall and runoff interrelationship. Thus, this research aims to study the rainfall-runoff inter-relation, predict flash floods, and to map the risk areas in Jazan Province by the geological, geomorphological, and hydrogeological characteristics along with digital elevation model (DEM), watershed modeling system (WMS) and HEC-HMS models. Jazan Province encompasses 25 drainage basins, receiving a considerable amount of rainfall (ranging from 100 to 500 mm) (August, October-November, March) which intermittently cause strong and destructive flash floods. The DEM was used for delineating the catchment (drainage basins) parameters. Physiographic parameters of the catchments have been analyzed for mapping the hazard degree of the flash flood strength. Further, basins with high hazard degrees of flash floods were selected to assess rainfall-runoff inter-relation using the HEC-HMS models, GIS, and morphometric parameters. Forty %, 8%, 52% of the study area are high, medium, and low hazard degrees of flash floods, respectively. The groundwater recharge in the study area was calculated through the integration of satellite image analysis, SWAT and GIS techniques and it ranges from 0.002 mm/km2/year to 8 mm/km2/year with an average of 2.5 mm/km2/year. Rainfall-runoff inter-relation of study basins, assessed based on the integration of WMS and HEC-HMS models, indicates that the resulting runoff volume ranges from 18.5 × 106 m3 to 473.1 × 106 m3 at a recurrence period of 5 and 100 years at rainfall events of 65 mm and 116.8 mm, respectively.

Geospatial techniques to determine Coastal geomorphology changes along the Cuddalore and Nagapattinam coast, Tamil Nadu, India

This study proposes to use geospatial techniques to assess coastal geomorphological changes along the southeast coast of India, from Cuddalore to Nagapattinam. The results will provide insights into regional morphology changes and will advance our understanding of coastal evolution, sea level variations and quaternary geomorphic processes. The coastal geomorphological units of the study area comprise of the coastal zone and an older deltaic plain. Most coastal zone features have developed through erosion, accretion and other natural processes. These features can be classified as depositional or erosional. By analyzing satellite imagery from 1980 to 2020, the study identified changes in coastal geomorphological features. This information can be used to locate mineral deposits, hydrocarbon locales, groundwater targets and sites for artificial recharge and saltwater intrusion mitigation. It can also affect coastal zone management decisions.

High-resolution automated detection of headwater streambeds for large watersheds

Abstract. Headwater streams, which are small streams at the top of a watershed, account for the majority of the total length of streams, yet their exact locations are still not well known. For years, many algorithms were used to produce hydrographic networks that represent headwater streams with varying degrees of accuracy. Although digital elevation models derived from lidar have significantly improved headwater stream detection, the performance of the algorithms on landscapes with different geomorphologic characteristics remains unclear. Here, we address this issue by testing different combinations of algorithms using classification trees. Homogeneous hydrological processes were identified through Quaternary deposits. The results showed that in shallow soil that mainly consists of till deposits, the use of algorithms that simulate the surface runoff process provides the best explanation for the presence of a streambed. In contrast, streambeds in thick soil with high infiltration rates were primarily explained by a small-scale incision algorithm. Furthermore, the use of an iterative process that simulates water diffusion made it possible to detect streambeds more accurately than all other methods tested, regardless of the hydrological classification. The method developed in this paper shows the importance of considering hydrological processes when aiming to identify headwater streams.

Why coastal lagoons are so productive? Physical bases of fishing productivity in coastal lagoons

Coastal lagoons are among the most productive marine ecosystems in the world. Annual primary production varies from 50 to > 500 g C m−2 year−1, being of the same order of magnitude as that of the upwelling areas. Many lagoons lie within the range of eutrophic (300–500 g C m−2 year−1) or hypereutrophic (> 500 g C m−2 year−1) conditions. The high productivity of coastal lagoons makes them subject of exploitation by many marine fishes and invertebrates, that use them as nursery areas and feeding grounds during their early life cycle phases, and most lagoons support important fisheries or maintain aquaculture exploitations. The high levels of their biological production can be explained by some of their common features as shallowness and the strong influence of terrestrial systems. Shallowness favors that the photic zone extends to the lagoon bottom and that wind can promote the resuspension of nutrients and organisms. The interaction with land also introduces significant amounts of nutrients. However, trophic variables can explain < 43 % of the fishing yields, and further than the trophic status of the lagoons, several works showed that the biological productivity of coastal lagoons can be explained by their geomorphological features such as the positive influence of shoreline development and the negative influence of depth. Using the Mar Menor lagoon as a case study, we propose that although nutrient inputs and light can be limiting factors for photosynthetic based productivity, increasing fishing yield up to a certain limit, the productivity of lagoons is mainly promoted by more general forces associated to physical and chemical gradients.