Geomorphological Setting Research Articles

Land subsidence in Isfahan metropolitan and its relationship with geological and geomorphological settings revealed by Sentinel-1A InSAR observations

Recent reports from Isfahan, Iran, have proclaimed cases of land subsidence arising from persistence of drought events and groundwater overexploitation. In this light, the present study attempts to conduct an PS-InSAR analysis of subsidence events using the Sentinel–1A Synthetic Aperture Radar imagery technique, in order to develop a subsidence map of the target study region, covering the period from October 16, 2014 to November 22, 2019 as well as to investigate its relation to geological/geomorphological factors. Toward this end, the methodology proceeds to detect land subsidence phenomenon across the Isfahan Metropolitan area, situated on the Zayande-Rud River Terrace (ZRT) and Isfahan Alluvium Plain (IAP). A total of 198 Sentinel images were used to derive deformation specifics observed throughout ZRT & IAP by dint of incorporating ascending and descending passes of the InSAR technique. As maintained by spatial and temporal variation maps of surface deformations in the urban regions of Isfahan, ZRT & IAP have undergone various orders of subsidence throughout the observation period, at an estimated rate of −5 to −100 mm/year. Overall, land subsidence appears to increase from south towards the northern, northeastern, and eastern sectors of Isfahan Metropolitan, while the southern sectors are nearly a stable area. This study indicates that the spatial subsidence pattern during the study period corresponds closely to the spatial distribution of ZRT & IAP in the Isfahan Metropolitan area.

Evolução holocênica das encostas da bacia do riacho Bruscas, Nordeste do Brasil

Localizada na Província Geológica da Borborema, a bacia do Riacho Bruscas constitui importante amostra do contexto geomorfológico e geológico do setor oriental do Nordeste do Brasil, onde a morfogênese e suas implicações paleoclimáticas são particularmente distintas daquelas que afetam áreas do sul e sudeste do país. O presente trabalho tem como objetivo analisar encostas com coberturas coluviais da bacia do Riacho Bruscas, tomando como base as características dos sedimentos, sua cronologia absoluta (LOE), geometria, estrutura e arranjo estratigráfico. Apesar de fragmentários, disjuntos espacialmente, e originários de intensidades distintas, esses materiais podem fornecer informações importantes sobre a dinâmica geomorfológica que, em última instância, reflete a ação dos componentes paleoambientais sobre a organização das unidades agradacionais do relevo. Os resultados foram agrupados em função dos dados coletados em quatros setores distintos da bacia, onde ocorrem depósitos coluviais, de forma a abranger todos os contextos morfológicos que, na área, resultaram na acumulação de sedimentos de encosta. Os depósitos estudados apresentaram-se confinados em intervalo de tempo que alcança desde o limiar Pleistoceno/Holoceno até a Pequena Idade do Gelo. Contudo, enquanto os depósitos resultantes da reumidificação geral observada ao final do Pleistoceno são ubíquos nas demais áreas do Nordeste semiárido, os depósitos do Holoceno médio e superior apontam para ocorrências mais localizadas, provavelmente relacionadas à ação de eventos pluviais orograficamente condicionados, mais intensos sobre o maciço da Serra da Baixa Verde e outros setores elevados do Planalto da Borborema.

Development of cosmogenic nuclide capabilities in South Africa and applications in Southern African geomorphology

ABSTRACT Cosmogenic nuclide (CN) applications offer methods to quantify rates of landscape change and of dating geomorphological deposits and surfaces. Over the past two decades, CNs have been used to determine denudation rates, constrain uplift rates and determine burial ages of sediments in different geomorphological settings across the Southern African landscape. Here, we first give an overview of the landscape evolution of Southern Africa and how CN-based studies have contributed to this subject. Then we give a compilation of CN denudation data from Southern Africa, which show that average erosion rates have decreased by an order of magnitude since the late Cenozoic. Finally, we present the state of CN infrastructure and capabilities in South Africa as well as envisaged future developments. An Accelerator Mass Spectrometer (AMS) has become operational for carbon-14, beryllium-10 and aluminium-26 measurements at the National Research Foundation (NRF) iThemba Laboratory for Accelerator Based Sciences (LABS) in Gauteng since 2017. The measurements’ accuracy and precision compare well with other AMS laboratories internationally. Local sample preparation laboratories are currently available with limited capabilities and are mostly still under development.

Launch of the Atlas of Silk Road Disaster Risk

The Silk Road which links four ancient civilizations is a well-known ancient trade and cultural exchange route. It linked the China and the west for more than two thousand years in the past. The present Silk Road which inherits the spirit of ancient Silk Road covers more than 140 countries and nearly 66% world population (Cui et al.2017; Lei et al. 2018). However, due to the complex geological and geomorphological settings and increasing number of extreme weathers under global warming, the number of natural hazards reported in the Silk Road area has been increasing year by year, and they had been getting worse in recent years (e.g., earth-quakes, landslides, and debris flows, floods, droughts). This trend poses huge threats to the Silk Road countries and their livelihoods (Lei et al. 2018; Cui et al.2018a; Cui et al.2018b). Furthermore, many countries in this area are less developed countries and this increasing occurrence of disasters could significantly hinder the sustainable development of Silk Road countries. In line with Sendai Framework for Disaster Risk Reduction 2015-2030 and 2030 Agenda for Sustainable Development, the Silk Road Disaster Risk Reduction (SiDRR) was launched in 2016 as an international research program on disaster risk reduction (Lei et al. 2018). This program is tasked to enhance global actions towards the green and resilient Silk Road by joint forces of over twenty research institutes and scientists around the globe. For making a step to enhance understanding the disaster risks, SiDRR is ready to consolidate its research results by publishing the Atlas of Silk Road Disaster Risk in 2020. The Atlas provides the details of environment, disaster characteristics, typical disaster events, and disaster risk assessment results at different scales in the Silk Road area in an envisioned form.

Habitat Management Based on Mangrove Sensitivity Assesment in Tulungagung Coastal Area

Tulungagung reflects the typical conditions of southern coast of Java, which dominated bay small bays with thin layer of superficial mud sediments and bordered by hilly terrain. Mangrove distribution in Tulungagung located in there locations, Brumbun Beach, Gerangan Beach and Sine Beach. This research aimed to identify the forest structure, habitat sensitivity and completed with management plan in each location. Data collected includes vegetation structure, hydrooceanography, environmental pressure and anthropogenic activities. An interesting finding is that, despite its narrow areas (2,24 Ha), mangroves in Tulungagung have high species diversity (11 species of true mangrove includes Acanthus ebracteatus, Acanthus ilicifolius, Acrostichum aureum, Avicennia alba, Avicennia marina, Ceriops tagal, Excoecaria agallocha, Rhizopora apiculata, Rhizopora mucronata, Rhizopora stylosa dan Sonneratia alba). Rm and Rs stands dominated by >7m height with canopy cover range from 79,4-89,6%. Geomorphological settings and limited mud supply are the primary challenges for mangrove habitat in Tulungagung. On the other hand, observation conservation status and local stakeholders involvement show the need for improvement of mangrove management in Tulungagung coastal areas.

Unraveling Spatial and Temporal Heterogeneities of Very Slow Rock-Slope Deformations with Targeted DInSAR Analyses

Spaceborne radar interferometry is a powerful tool to characterize landslides at local and regional scales. However, its application to very slow rock slope deformations in alpine environments (displacement rates < 5 cm/year) remains challenging, mainly due to low signal to noise ratio, atmospheric disturbances, snow cover effects, and complexities resulting from heterogeneous displacement in space and time. Here we combine SqueeSARTM data, targeted multi-temporal baseline DInSAR, GPS data, and detailed field morpho-structural mapping, to unravel the kinematics, internal segmentation, and style of activity of the Mt. Mater deep-seated gravitational slope deformation (DSGSD) in Valle Spluga (Italy). We retrieve slope kinematics by performing 2D decomposition (2D InSAR) of SqueeSARTM products derived from Sentinel-1 data acquired in ascending and descending orbits. To achieve a spatially-distributed characterization of DSGSD displacement patterns and activity, we process Sentinel-1 A/B images (2016-2019) with increasing temporal baselines (ranging from 24-days to 1-year) and generate several multi-temporal interferograms. Unwrapped displacement maps are validated using ground-based GPS data. Interferograms derived with different temporal baselines reveal a strong kinematic and morpho-structural heterogeneity and outline nested rockslides and active sectors, that arise from the background displacement signal of the main DSGSD. Seasonal interferograms, supported by GPS displacement measurements, reveal non-linear displacement trends suggesting a complex response of different slope sectors to rainfall and snowmelt. Our analyses clearly outline a composite slope instability with different nested sectors possibly undergoing different evolutionary trends towards failure. The results herein outline the potential of a targeted use of DInSAR for the detailed investigation of very slow rock slope deformations in different geological and geomorphological settings.

The assessment of soil chemical, physical, and structural properties as landslide predisposing factors in the Serra do Mar mountain range (Caraguatatuba, Brazil)

Landslides have environmental, social, and economic impact in the Brazilian Atlantic coast (Serra do Mar). In addition to meteorological, geological, and geomorphological settings, mineralogical and pore space heterogeneities in soil covers are considered important characteristics that can influence landslide occurrence. Since soil covers are very clayey, the evaluation of macro- and micromorphological soil features (soil structures, soil materials, and pores) resulted by mass movement during slope instability is difficult. This field of investigation practically does not exist in the Serra do Mar. The objective of this paper is to analyze the soil cover in a toposequence to identify macro- and microscopic soil features resulted from landslide processes, and assess the role of pedogenesis on landslide development. Macro- and micromorphological approaches were used to study the architecture of the soil cover and soil was sampled to determine chemical and mineralogical composition by XRF and XRD. Undisturbed clods were used to determine pore size and pore compartment by mercury porosimetry. It was recognized a brecciated and an undulating parallel-striated fabric. Both features were generated from mass movement and were unclear in the clayey horizons in the bottom of the toposequence. In this level, the occurrence of mottles suggesting short-term soil saturation and the presence of micropores < 1000 nm in soil could be the factors that drive soil movement downslope.

Waterfalls: Forms, Distribution, Processes and Rates of Recession

Abstract A waterfall is a very steep (commonly nearly vertical) fall of some magnitude in a river course. Waterfalls are widespread fluvial landforms that have been described from many parts of the world. Thirty-eight World Heritage Properties include waterfalls in their designation. In addition, some waterfalls are actual or potential geomorphosites. Waterfalls occur in almost all climatic environments, though they are particularly common in formerly glaciated areas. They occur on a huge diversity of rock types, although in general, they do not form persistent or large falls on soft or unconsolidated rocks. Waterfalls also occur in a wide range of geomorphological settings: glaciated areas, areas of active tectonism, areas of sea-cliff retreat and sea-level change, great escarpments on passive margins, basins with river capture, rifted and faulted areas and areas that have been subjected to megaflooding. Multiple processes account for waterfall retreat and varying rates of recession. Although the greatest interest has been in rates of waterfall recession, there are examples of waterfalls that prograde as a result of tufa deposition.

Alpine hydrogeology

Groundwater discharge in alpine headwaters sustains baseflow in rivers originating in mountain ranges of the world, which is critically important for aquatic habitats, run-of-river hydropower generation, and downstream water supply. Groundwater storage in alpine watersheds was long considered negligible, but recent field-based studies have shown that aquifers are ubiquitous in the alpine zone with no soil and vegetation. Talus, moraine, and rock glacier aquifers are common in many alpine regions of the world, although bedrock aquifers occur in some geological settings. Alpine aquifers consisting of coarse sediments have a fast recession of discharge after the recharge season (e.g., snowmelt) or rainfall events, followed by a slow recession that sustains discharge over a long period. The two-phase recession is likely controlled by the internal structure of the aquifers. Spatial extent and distribution of individual aquifers determine the groundwater storage-discharge characteristics in first- and second-order watersheds in the alpine zone, which in turn govern baseflow characteristics in major rivers. Similar alpine landforms appear to have similar hydrogeological characteristics in many mountain ranges across the world, suggesting that a common conceptual framework can be used to understand alpine aquifers based on geological and geomorphological settings. Such a framework will be useful for parameterizing storage-discharge characteristics in large river hydrological models.

Integrated assessment of contemporary hydro-geomorphologic evolution of the Indus River Estuary, Pakistan in context to regulated fluvial regimes

The riverine ecosystem is dependent upon the supply of fresh water but the decrease in flows weakens this connection. It gradually leads to impairment of ecologic as well as geomorphologic settings of a riverine ecosystem. Keeping this in view, the present study was designed to assess the contemporary evolution of the Indus River Estuary (IRE) under forced hydrological conditions. An account of transitions in the eco-geomorphologic response of the IRE was synthesized using satellite imageries from 1972 to 2016 and interpreted with the ground observations. Due to flow regulations, an 80% decrease in average annual flow and 50% dampening of flood peaks have altered its hydrological regime. These pronounced hydrological shifts have also played a significant role in the modulation of channel morphology.Similarly, the morphological configuration of the estuary like the length and width of the channel have also increased by 11% and 29%, respectively, and the rate of erosion was more than the deposition. After experiencing significant variations in the rate of lateral migration, the channel has started creeping in a south-eastern direction dominantly since 1993, with an average rate of migration of 44 m/yr. Correspondingly, the riparian landscape has also evolved coherently with a notable competition between bare land and the vegetative cover. Trade-offs between the river hydrology, channel morphology and landscape ecology were understood with a correlation matrix and interpreted with plausible causes. It would help the policymakers to assess the overall ecological health of the IRE and contribute the experts working on designing a framework for the study of system dynamics.

Do the morphological characteristics of Chilean gravel-bed rivers exhibit latitudinal patterns?

Gravel-bed rivers exhibit remarkable dynamics and distinctive morphological patterns which influence the biological processes, as well as the river ecosystem resilience to human impacts. Classifications of river ecosystems into groups with morphologically distinct patterns are therefore of paramount importance for a better understanding of their dynamics, their management and conservation.Investigations on fluvial morphology and the related dynamics in Chilean gravel-bed rivers are still scarce, and, so far, no efforts have been made to identify latitudinal patterns of their morphological characteristics that may serve as a basis for further classification purposes. In fact, the great variability in bio-geographic, climatic, geologic and geomorphologic settings of the country offer an almost unique opportunity to study how the morphological characteristics of gravel-bed rivers may vary within extremely heterogeneous environments.We performed a regional analysis of nineteen Chilean gravel-bed rivers, from semi-arid Mediterranean to rainy temperate conditions (latitude ranging from 32° S to 39° S). Planform characteristics within these reaches were identified through interpretation of satellite images. Topographic features of the river basins were derived from open source digital elevation models and water discharge values were obtained from available national databases.We addressed the following research questions: a) can these 19 rivers be grouped into clusters considering their distinct planform characteristics of the river channel and basin features, as related to latitudinal gradients?, b) do river morphological characteristics vary along the analyzed latitudinal gradient?, c) does the distribution of specific geomorphic units (i.e. islands) follow a longitudinal pattern?, and finally, d) are these units associated to specific hidrogeomorfic characteristics?We generated a clustering which reflects latitudinal and morphological gradients in Chilean gravel-bed rivers, with the northernmost and southernmost rivers grouped according to their distinctive hydro-morphological characteristics and geomorphic units. We also observed a general tendency of an increase in the proportion of fluvial islands relative to the active channel area from the 33° Latitude in southward direction.

An integrated sea-land approach for analyzing forms, processes, deposits and the evolution of the urban coastal belt of Cagliari

ABSTRACT Using a comprehensive cartographic product, this paper aims to illustrate the evolution of the urban geomorphological setting of the urban coastal belt of Cagliari (southern Sardinia, Italy, western Mediterranean Sea). The geomorphological map (1:14,000) presented herein summarizes different data (e.g. urban development, anthropogenic features, geomorphological elements, recent deposits, sedimentological distribution, hydrodynamics and ecological components) acquired through an integrated sea-land approach and a multidisciplinary-multitemporal investigation. The main significant environmental changes are linked to urbanization, the development of port infrastructures (embankments along the shoreline and the construction of the canal harbour), remediation work and filling activities, and the hardening of dune and beach systems and cliffs. These man-made interventions have increased the vulnerability of the shore zones to flood hazards and risks, which are linked to sea-level rises and global warming.

Влияние заповедного режима на развитие горного рельефа Центральной Азии (на примере заповедника Аксу-Джабаглы)

The oldest nature reserve in the mountains of Central Asia Aksu-Zhabagly Nature Reserve was created more than 90 years ago. During this period, the conservation regime had a significant impact not only on biota, but also on exogenous processes in the reserve. In order to assess this influence, the staff of the Institute of Geography RAS conducted special geomorphological studies. A typological zoning of the reserve’s mountain relief was carried out in all high-altitude tiers: highlands, middle mountains and lowlands. A transitional zone characterizing large tectonic benches has been identified. For each type of relief, characteristic changes in the course of geomorphological processes associated with the cessation of anthropogenic pressure, mainly in the form of grazing and the establishment of a specially protected area, are determined. It was established that the general tendency to stabilize the slopes prevails, more noticeable in the mountains’ lower tier and practically absent in the high mountains. The reverse trend to processes intensify is noted in two geomorphological settings: in the Alpine highlands and in the foci of landslide development in the transition zone from the highlands to the middle mountains.

Analysing the sensitivity of Hungarian landscapes based on climate change induced shallow groundwater fluctuation

One of the undoubtedly recognizable consequences of the ongoing climate change in Hungary is the permanent change of groundwater depth, and consequently the sustainably reachable local water resources. These processes trigger remarkable changes in soil and vegetation. Thus, in research of sensitivity of any specific landscape to the varying climatic factors, monitoring and continuous evaluation of the water resources is inevitable. The presented spatiotemporal geostatistical cosimulation framework is capable to identify rearrangements of the subsurface water resources through water resource observations. Application of the Markov 2-type coregionalization model is based on the assumption, that presumably only slight changes have to be handled between two consecutive time instants, hence current parameter set can be estimated based on the spatial structures of prior and current dataset and previously identified parameters. Moreover, the algorithm is capable to take into consideration the significance of the geomorphologic settings on the subsurface water flow. Trends in water resource changes are appropriate indicators of certain areas climate sensitivity. The method is also suitable in determination of the main cause of the extraordinary groundwater discharges, like the one, observed from the beginning of the 1980’s in the Danube–Tisza Interfluve in Hungary.

Alpine Hydrogeology: The Critical Role of Groundwater in Sourcing the Headwaters of the World.

Groundwater discharge in alpine headwaters sustains baseflow in rivers originating in mountain ranges of the world, which is critically important for aquatic habitats, run‐of‐river hydropower generation, and downstream water supply. Groundwater storage in alpine watersheds was long considered negligible, but recent field‐based studies have shown that aquifers are ubiquitous in the alpine zone with no soil and vegetation. Talus, moraine, and rock glacier aquifers are common in many alpine regions of the world, although bedrock aquifers occur in some geological settings. Alpine aquifers consisting of coarse sediments have a fast recession of discharge after the recharge season (e.g., snowmelt) or rainfall events, followed by a slow recession that sustains discharge over a long period. The two‐phase recession is likely controlled by the internal structure of the aquifers. Spatial extent and distribution of individual aquifers determine the groundwater storage‐discharge characteristics in first‐ and second‐order watersheds in the alpine zone, which in turn govern baseflow characteristics in major rivers. Similar alpine landforms appear to have similar hydrogeological characteristics in many mountain ranges across the world, suggesting that a common conceptual framework can be used to understand alpine aquifers based on geological and geomorphological settings. Such a framework will be useful for parameterizing storage‐discharge characteristics in large river hydrological models.

Geological and geomorphological analysis of a complex landslides system: the case of San Martino sulla Marruccina (Abruzzo, Central Italy)

ABSTRACT This work deals with the landslides affecting the area surrounding the village of San Martino sulla Marrucina and involving the neighboring municipalities of Casacanditella and Filetto. The geological and geomorphological settings of this area are being discussed. The enclosed maps have been realized following a multidisciplinary approach, based on morphometric, geological, and geomorphological analyses and supported by air-photo interpretation, dendrochronology, and satellite SAR interferometry (InSAR). The map is organized in four sections: orography (on the upper part), geological map (on the upper right part), main geomorphological map (in the central left part, 1:7,500 scale), and multitemporal analysis (in the lower part). The aforementioned multi-temporal assessment of landslides was performed according to the geomorphological evidence-based criteria and the past ground displacement measurements were obtained by dendrochronology and InSAR. The aim of the study is to understand the evolution in time and space of this landslide area, focusing on the corresponding kinematics.

Effects of a Large Irrigation Reservoir on Aquatic and Riparian Plants: A History of Survival and Loss

Dammed rivers have unnatural stream flows, disrupted sediment dynamics, and rearranged geomorphologic settings. Consequently, fluvial biota experiences disturbed functioning in the novel ecosystems. The case study is the large irrigation reservoir Alqueva in Guadiana River, Southern Iberia. The study area was divided into three zones: upstream and downstream of the dam and reservoir. For each zone, species composition and land use and land cover (LULC) were compared before and after the Alqueva Dam implementation. Data consist of aquatic and riparian flora composition obtained from 46 surveys and the area (%) of 12 classes of LULC obtained in 90 riverine sampling units through the analysis of historical and contemporary imagery. There was an overall decrease of several endemic species and on the riparian shrublands and aquatic stands, although differences in the proportion of functional groups were not significant. Nevertheless, compositional diversity shows a significant decline in the upstream zone while landscape diversity shows an accentuated reduction in the reservoir area and downstream of the dam, which is likely related to the loss of the rocky habitats of the ‘old’ Guadiana River and the homogenization of the riverscape due to the irrigation intensification. The mitigation of these critical changes should be site-specific and should rely on the knowledge of the interactions between surrounding lands, ecological, biogeomorphologic, and hydrological components of the fluvial ecosystems.

Extreme wave events recorded in sedimentary archives of the Geropotamos River (north-central Crete, Greece)

Recent tsunami events have shown that tsunamis may propagate far inland by entering rivers mouths and may cause massive damage along the river banks. However, so far, only a few studies have been conducted such a search for studying tsunami signals in incised valley systems along the Mediterranean coasts although the tsunami hazard is high. The island of Crete is known to have been affected several times by strong tsunamis, e. g., by the AD 365 and the Late Bronze Age (LBA) Santorini tsunamis. The narrow Geropotamos River valley, distinctly incised into local bedrock and located at the northern coast of Crete and fully exposed to the Cretan Sea, was selected as a promising natural setting to search for palaeotsunami signatures in fluvial sedimentary archives. Based on a multi-electrode geoelectrical survey and a set of sediment cores, we investigated the event-geochronostratigraphic record of both the Geropotamos River mouth area and the river valley ca. 1 km upstream by means of sedimentological, geo-chemical, geochronological, geomorphological, and micropalaeontological methods. The sedimentary environment towards the present-day river mouth is dominated by (fluvio-)lagoonal muds since the mid- Holocene. These lagoonal sediments are intersected by six coarse-grained sand layers each representing an extreme wave event (EWE). EWE layers are up to several decimetres thick and are characterized by an allochthonous foraminiferal assemblage comprising shallow marine to open marine species. Also ca. 1 km further upstream, the sedimentary record revealed grain size and microfossil evidence of two high-energy events showing a clear marine imprint. Based on this, we suggest inundation from the seaside that reached minimum 1 km inland and left EWE signatures in a presently inactive external bank position of the Geropotamos River. Considering the sedimentary characteristics, the local wind and wave climate of the Cretan Sea, and the overall geomorphological setting, we interpret these EWE layers as tsunami- related. A major hiatus identified in the Geropotamos River mouth sediments seems to be related to the LBA Santorini tsunami as can be inferred based on local age-depth relations. The LBA tsunami is known to have severely hit the northern coast of Crete. However, the hiatus may also reflect changes in the subsidence rate and the local accommodation space architecture. The youngest EWE signal in the Geropotamos River archive appears to have been caused by the AD 365 tsunami event. Candidate deposits for both tsunami deposits were identified ca. 1 km further inland. Evidence of EWE impact documents channelling and acceleration effects of intruding water masses caused by the narrow and steeply incised Geropotamos River valley in an upstream direction. Further geochronological studies based on OSL dating are necessary for a reliable age control of these EWE candidate layers.

Spatial and temporal variations in source, diagenesis, and fate of organic matter in sediments of the Netravati River, India

AbstractOrganic matter (OM) such as organic nitrogen plays a substantial role in the global biogeochemical cycling of bio‐reactive components—amino acids (AA) in aquatic environments. Spatial and temporal variations in source, diagenesis, and fate of organic nitrogen such as AA in sediments of small tropical rivers and the role of oxbow/meandering loops under changing climatic conditions are poorly investigated. This study assessed the spatial and seasonal variations in OM composition, source, and diagenesis of a tropical small mountainous river—Netravati River, India, for 1 year. Water samples were determined for suspended particulate matter, and surface sediments were examined for bulk parameters, surface area (SA), and the L‐ and D‐enantiomers of AA. The L‐ and D‐enantiomers of AA displayed subtle seasonal variations in composition and depicted varying degrees of diagenesis. The concentration of D‐enantiomer of AA was high and showed substantial contributions from bacteria, terrestrial source, and in situ production. The D‐arginine was the most abundant D‐enantiomer of AA in the study area, possibly due to extracellular secretion by bacterial species and adsorption onto sediments, and thus, it was protected from degradation. Degradation index was more negative at the oxbow and meandering loop stations during the dry season suggesting that local geomorphologic settings steer the diagenesis of OM within the river. A negative relationship between gamma‐aminobutyric acid and organic carbon:surface area (OC:SA) ratio and a positive correlation between tyrosine and OC:SA ratio suggested accelerated loss of OM. Furthermore, the concentrations of most bulk parameters were higher in the lower reaches during monsoon and premonsoon seasons. Taken together, changes in seasons have an operational control in distinguishing the composition, source, and diagenesis of spatial OM distribution. Moreover, oxbows and river meandering loops influence the diagenetic processes in small tropical river systems.

Multiple Effects of Intense Meteorological Events in the Benevento Province, Southern Italy

In October 2015, two intense rainfall events hit the central and southern regions of Italy and triggered a combination of different and widespread effects, including floods, landslides, and soil erosion. These outcomes devastated about 68 municipalities of the Benevento province (Campania region), killed two people, and caused millions of euros worth of damage to structures, infrastructures, and agriculture. The town of Benevento was one of the sectors most affected by overflow. Extensive areas characterized by flyschoid outcrops experienced widespread occurrences of soil erosion and landslides, and destructive, high-velocity debris flows (about 50) afflicted areas that had experienced heavy rainfall of higher intensity (total rainfall of 415.6 mm). In this study, the characteristics of these rainfall events and related geomorphological processes were determined by (i) analyzing the available rainfall data to identify the spatial pattern, distribution, and statistical characteristics of the two storms and (ii) mapping the storm effects, such as flooded areas, landslide types, and soil erosion. These effects were then related to the spatial distribution of the storms and the local geological and geomorphologic settings that drove their initiation and development.