bluuebunny/crossref_metadata_2025 huggingface dataset:
The rainfall-triggered landslide event of November 1983 in the Lisbon Region: a contribution for the knowledge of regional slope instability
Authors: Morais Ana Rita , Oliveira Sérgio C. , Pereira Susana , Zêzere José Luís
Published: June 2022

On November 18, 1983, a heavy and short-duration rainfall event (164 mm/24 hours ) occurred, particularly, in the northern Lisbon metropolitan area, associated with an atmospheric  depression, localised southwest of the Azores islands, which evolved into a cut-off depression. This rainfall event triggered a large number of landslides, with evident regional importance, which remained little explored until now.

Event-based landslide inventories identify the location of landslides caused by a single trigger, which is crucial to understand the predisposition factors and to assess landslide susceptibility for different types of landsides occurring in the study area. The purpose of this study is to elaborate a complete event-based landslide inventory for this rainfall-triggered event, which is used  to model landslide susceptibility at the regional scale, helping to understand the combined action of the trigger and the landslide predisposing factors.

The landslide inventory is built based on the interpretation of high-resolution analogic aerial photographs (1:15,000 scale), obtained after the event, between the 8th and the 13th December 1983. Recent orthophotomaps covering the complete study area were used as the baseline image for the process of geo-referencing the aerial photos. In addition, it was necessary to perform local correction of deformations, resulting from the conic projections of aerial photographs, to improve the geometry of landslide limits. The landslide inventory allows to identify the landslide event spatial extension as well as to characterize the landslide typology, landslide morphometric parameters and event magnitude.

The landslide susceptibility is assessed using the event-based landslide inventory and a set of geo-environmental landslide predisposing factors that are modelled with the statistical method of the Information Value. The obtained results are interpreted taking in account the combination of landslide predisposing factors, but also of the spatial distribution of the rainfall that triggered the landslide event.

 

Acknowledgements

This work is part of the project Riskcoast - Development of tools to prevent and manage geological risks on the coast linked to climate change (SOE3/P4/EO868, Interreg Sudoe). Sérgio C. Oliveira is funded by FCT - Portuguese Foundation for Science and Technology, I.P., through the project BeSafeSlide - Landslide Early Warning soft technology prototype to improve community resilience and adaptation to environmental change (PTDC/GES-AMB/30052/2017) and by the Research Unit UIDB/00295/2020, UIDP/00295/2020.
Karst relief of Mali me Gropa Massif, Central Albania: specifics and spatial differentiation  
Authors: Andreychouk Viacheslav , Eftimi Romeo , Nita Jerzy , Klimchouk Alexander
Published: June 2022

The mid-altitude mountain massif of Mali me Gropa in the central part of Albania rises to an altitude of 1500–1800 m above sea level, is composed mostly of Mesozoic limestone. It is characterized by very extensive surface karst development dominated by dolines, distribution of which creates the polygonal pattern. This study provides a detailed field and GIS-based geomorphological analysis of the western part of Mali me Gropa massif aimed to determine and explain the morphometric and morphological diversity of the relief. Using the homogeneity criterion, a number of geomorphological units with specific varieties of karst relief have been distinguished. The differences concern the size (diameter) of the forms (dolines and depressions), their depth, shape and symmetry, orientation, the density of occurrence and the spatial pattern. The differentiation of the karst relief is explained by the influence of such factors as: evolutionary (geological and geomorphological evolution of the massif), hypsometric (altitude differentiation of terrains) and geomorphologic-structural (inclination of the slopes and layers). The relatively poor expression of open karst conduits (i.e. caves and vertical shafts) on the surface of the massif may result from relative immaturity of the epikarst zone, the widespread occurrence of residual cover on the plateau, and the accumulation of large amounts of clay material in dolines and depressions. Detailed hydrogeological studies show, however, high karst permeability and dominance of conduit flow. Geomorphological and karstological research of the massif should be continued as it represents a type of karst massif found also in other parts of Albania and the entire Mediterranean region. Karst areas of this type are of great economic (large reservoirs of good quality water) and nature protection (specific environment) importance.

 
The Waipaoa River Story: how changing connectivity modulates catchment-scale response times and prospective river futures
Authors: Fuller Ian , Brierley Gary , Rosser Brenda , Tunnicliffe Jon , Marden Mike
Published: June 2022

The 2208 km2 Waipaoa River catchment, the onshore portion of the Waipaoa source-to-sink (S2S) sedimentary system in the East Coast of New Zealand’s North Island, is a tremendously data-rich study area for obtaining insights into catchment function and connectivity (Kuehl et al. 2016). There have been longstanding concerns about erosion severity and mitigation dating back to 1895 (Hill, 1895). High rates of erosion in the Waipaoa have been the defining catchment management issue since the mid-twentieth century, triggered by forest clearance for pastoral agriculture in the late nineteenth and early twentieth century and primed by a combination of highly erodible lithologies, steepland terrain, regular intense storm events, and slopes undercut by postglacial river incision. The magnitude of erosion in the East Coast Region since European forest clearance has exceeded that in any other part of New Zealand.  Connectivity relationships in the Waipaoa catchment have been profoundly altered. Simultaneous sediment inputs from deforested slopes deliver sediment directly into tributary and trunk stream channels, causing significant bed aggradation and channel infilling. Gullies overwhelm receiving streams, forming alluvial fans and represent the single largest source of sediment to the system. Sediment derived from shallow landslides is significant during storm events, but gully, sheet and riverbank erosion have the potential to generate sediment whenever it rains. In the upper catchment, channel widening contributes further sediment, particularly through bank and cliff erosion. The fine-grained nature of sediment supplied by lithologies in the upper catchment accentuates downstream delivery of materials, resulting in channel contraction and floodplain accretion in the lower Waipaoa.  Efforts to mitigate erosion by afforestation using plantation forestry have been successful in some headwater tributaries, with channel degradation beginning, but this process generates additional sediment, which is conveyed downstream. We use a combination of LiDAR and river channel cross-sections to demonstrate contemporary longitudinal patterns of connectivity in the Waipaoa River and assess the prospective river futures of this anthropogenically altered system.

 

References

Hill, H. (1895) Denudation as a factor of Geological Time. Transactions and Proceedings of the New Zealand Institute, 1895, Volume XXVIII.

Kuehl, S. A., Alexander, C. R., Blair, N. E., Harris, C. K., Marsaglia, K. M., Ogston, A. S., Orpin, A. R., Roering, J. J., Bever, A. J. & Bilderback, E. L. 2016. A source-to-sink perspective of the Waipaoa River margin. Earth-Science Reviews, 153, 301-334.
Characterizing the role of supraglacial debris thickness variability on underlyingice ablation
Authors: Beck Calvin , Nicholson Lindsey , Wirbel Anna , Simon Thorsten
Published: June 2022

Projections of future climate implicate the thickening of debris-covered glaciers. Thus it becomes
increasingly important to consider the influences of the debris layer on glacier melt especially
because of the strong non-linear relationship between debris thickness and ablation rate. This
relationship is known as the Østrem curve. For very thin debris layers ablation is increased due to a
higher albedo where as thicker debris layers reduce ablation due to insulation. Some local scale
models based on satellite images already partly account for this effect. They take the average debris
thickness per decametre large grid cells and scale the ablation based on a representative Østrem
curve. Unfortunately, supraglacial debris thickness has been shown to vary substantially over short
length scales on a glacier surface. The debris thickness frequency distribution is also non-linear, with
varying skew and kurtosis. Therefore sub-debris ice ablation is a result of the combined non-
linearities of the particular Østrem curve with the particular frequency distribution of the debris
thickness.
In this study, we investigate the error of the ablation rate introduced by neglecting debris frequency
distribution. We obtained the Østrem curves from field measurements and different numerical
models. A gamma distribution with different rate and shape parameters was used to represent likely
debris thickness frequency distribution. The analysis shows that the debris frequency distribution
has a strong effect on calculated glacier melt. For some cases, this can result in a doubling or
tripling of ablation values in comparison to that calculated using the mean debris thickness.
Therefore neglecting this effect in numerical models has the potential to drastically underestimate
glacier melt.
Within the framework of this study, an interactive application was developed that allows one to
investigate the error on ice ablation if not considering the debris layer's thickness frequency
distribution.
Large drainage rearrangement in South America: the capture of the high São Francisco catchment by the Grande (Paraná) River
Authors: Salgado André , Rezende Eric , Paixão Rodrigo , Castro Paulo
Published: June 2022

This work research fluvial piracy processes between two of the fifty largest catchments in the world: the Paraná and São Francisco ones, in South America. The study area comprises the Furnas Lake of the Furnas Hydroelectric Plant, in the south-west portion of Minas Gerais State, Brazil. In this region, the Paraná River is called Grande River and its catchment forms a large "amphitheater" facing north, towards the São Francisco catchment. The research method was based on: remote sensing, in order to identify drainage anomalies; the use of the Seppômen computational tool, to reconstruct paleotopographic evolution; and by field work, to confirm/improve remote sensing interpretations and to also obtain sedimentary and geomorphic data. Nowadays, the drainage divider between the two catchments is characterized by a series of mountain ranges and plateaus. However, in the region of Furnas Lake, near the village of Pimenta, there is an anomalous low divider between the two catchments. This anomalous low divider is located 25 km north of a 90° elbow that changes the direction of the Grande River from north (towards the São Francisco catchment) to west (towards the Paraná Sedimentary Basin) and corresponds to an expressive morphological record of paleo-valley that seems to have connected the two hydrographic basins currently separated. In the region of the low divider, on the top of a hill located in the paleo-valley on the São Francisco catchment side, next to the current headwaters of its tributaries, a pebbly fluvial Pleistocene unit (deposit of ancestral river before the beginning of the incision stage or being and old terrace) indicates that a major river flowed by the actual divide, in the past. In addition, the elbow that changes the direction of the Grande River makes it cross a quartzite mountain range through a series of river gorges, before entering in the Paraná Sedimentary Basin. The obtained Seppômen maps demonstrate that near the drainage elbow point the relief was about 400 m higher than it is now, configuring an old drainage divider along the quartzite mountain range. Furthermore, in the northern portion of the elbow, the topographical reconstruction maintained the valley morphology indicating that the Grande catchment had a connection with the actual São Francisco catchment. These evidences indicate that a major drainage rearrangement occurred between the two catchments, where a paleo-Grande (Paraná) River captured the ancestral upper São Francisco River catchment. This fluvial piracy was responsible for a capture of more than 50000 km2 and by the fact that the former source of the São Francisco River is now the current source of the Paraná River.
Quantitative assessment of the rockwall-talus slope system morphodynamics using TLS monitoring data (Tatra Mts., Poland). 
Authors: Rączkowska Zofia , Cebulski Jarosław , Gądek Bogdan , Kajdas Joanna
Published: June 2022

The system rockwall-talus slopes is very common in the high-mountain. It develops mostly due to rapid mass movements, like rockfalls and debris flows. The quantitative data about changes of slopes and sediment transfer within the system enable to get to know complexity and controls of its morphodynamics. Using data from multi-annual temporal  monitoring by terrestrial laser scanning (TLS) survey of the rockwall-talus slope systems we examine their functioning in context of cooperation of rapid mass movements. The attention is paid to showing the different pattern of sediment transfer through the system and its controls.

The study were made in the Tatra Mts. The two adjacent rockwalls and talus slopes systems at the head of the Rybi Potok valley was monitored using terrestrial laser scanning TLS during last decade (2011-2021). They extend between ~1400 and 2500 m a.s.l. Their morphometric parameters are similar, but there is small hanging glacial cirque in one of them. The data was supplemented by meteorological data from the stations located in the bottom of the cirque and at the base of talus slopes.

The rockfall events occurred on the rockwall in each of the systems, which provided few thousands or dozen thousands of loose sediments to talus slopes. It was found that rockfalls occurred in effect of coupling geological and thermal conditions of rocks, not as result of permafrost degradation. The sediment transfer mechanism differs between the systems. The material transported by rockfalls was mostly deposited at the bottom of glacial cirque, while at adjacent system was transported to the apex of talus slope. Therefore activity of two adjacent talus slopes varies. The results showed that changes in talus slopes are essentially effects of debris flows. Their final effect is building up of the talus slope, even if the debris flows moved part of the debris sediments out. The studies reveal and confirm the importance of interplay between different extreme morphogenetic processes and show the complexity of talus slope transformation. A single input of loose debris from a massive rockfall dominated the effectiveness of debris flows. The studies also demonstrated differentiation of spatiotemporal pattern of sediment transfer trough rockwall-talus slope system. Moreover, relations between rapid mass movements and extreme rainfall and temperature as a result of climate change were found.
How geomorphological processes conditioned the historical evolution of the Greek-Roman city of Tyndaris (Messina Province, Northern Sicily, Italy)
Authors: Bonasera Mauro , Parizia Francesco , Gregorio Francesco , Lanza Stefania , Perotti Luigi , Alberto Walter , Vitti Mario , Fubelli Giandomenico , Randazzo Giovanni
Published: June 2022

According to Pliny the Elder, ancient Tyndaris, one of the most important Greek-Roman colonies overlooking the southern Tyrrhenian Sea, rapidly declined in the First Century AD because of natural disasters. In Naturalis Historia, he dedicated an entire chapter to the cities carried away by sea storms and waves. Historical bibliographic research and a geomorphological survey have been performed to shed light on the occurred phenomena, flanked by UAV flights and photogrammetry. The nadir and off-nadir UAV flights allowed to observe out-of-reach areas of Tyndaris promontory. The generation of a high-resolution DSM and orthophotos and the export of the 3D model provided a basis for the structural analysis of the coastal cliff and allowed to map geomorphological elements. In particular, the fieldwork along the coastline highlighted landforms related to gravity as rockfall, rock avalanche and debris flow deposits rich of archaeological remains. The results gave clear information on how the geomorphological evolution weighed upon Tyndaris urban features.
Microslag as a stratigraphic tracer to quantify floodplain processes during the last centuries
Authors: Houbrechts Geoffrey , Kalicki Tomasz , Przepióra Paweł , Notebaert Bastiaan , Petit François
Published: June 2022

This research has two objectives: (I) to improve the methodology of using small-sized iron slag (microslag) as a stratigraphic marker to reconstruct the centennial-scale floodplain evolution and (II) to study the geomorphic evolution of the Ardennian rivers using the evaluation of the concentration of microslag in alluvia. In addition, 14C dating, topographic surveys and sedimentological analysis were carried out. Using these data, floodplain processes have been quantified in several Belgian rivers (Ardennes massif): fine floodplain sedimentation, lateral mobility rates and channel incision phases. A major hillslope erosion episode occurred during the Bronze Age. Archaeological data and historical sources indicate Roman and High Middle Age occupations in the area but no evidence of erosion or increased floodplain sedimentation have been observed. Several peat layers have been dated in the Chavanne floodplain to approximately 1000 BP and probably indicate very low anthropogenic activity and a high level of groundwater. Before 1000 CE, the fluvial style of the Ardennian rivers was probably different, characterized by a low-level forested floodplain, which explains the presence of frequent peat layers within the alluvial sequences and abandoned channels. From the eleventh century onwards, a generalized increase in sedimentation rates occurred, coinciding with a higher concentration of charcoal in the alluvium and also the formation of colluvial deposits. Analyses of slag concentrations allowed us to reconstruct the evolution of the floodplain topography. In Ardennian rivers, the mean floodplain aggradation over the last several centuries is between 3 and 20 cm/century, depending on the study site. Such differences in floodplain sedimentation rates can be explained by several factors such as the distance to past cultivation areas, the degree of woodland clearance, flow velocities during floods and the incision of the riverbed during last centuries, which reduces the frequency of inundation and, therefore, sedimentation on floodplains.
Vulnerabilities in Post Yaas Environment and Probable Mitigation Strategies: Case Studies from Selected Sites, Sundarban, India
Authors: Das Karabi , Das Kanailal
Published: June 2022

Abstract: Vulnerability not only establishes the relationships people have with their environment but also links the social forces and institutions and the cultural values that sustain them. Physiographically, a deltaic plain, the Sundarban region is a dynamic ecosystem which frequently witnesses physical and social vulnerability brought about by natural hazards like tropical cyclones resulting in saltwater flooding. The Bay of Bengal basin records the highest number of tropical cyclones globally. About 8 storms with sustained wind speeds more than 63 km/hr form in the Bay of Bengal, of which, 2 become tropical cyclones. Cyclone Yaas was identified as a very severe cyclonic storm, originally formed as a tropical disturbance identified by the India Meteorological Department (IMD) on 23rd May 2021. Yaas made it’s landfall at Dhamra of Orissa state of India, on 26th May 2021, coinciding with spring tide. Coastal flooding was reported from Maipith, Bhubaneswari village panchayats along the rivers Matla, Thakuran and Nimania of Kultali community development block, Dhaspara, Sumatinagar, Kastala, Kochuberia, Mahishamari, Muriganga, Shilpara village panchayats of Sagar community development block, Amrabati, Lakshmipur, Fraserganj of Namkhana community development block, Gobardhanpur, Mridangabhanga, Krishnadaspur, East Chintamanipur, Kumarpur of Patharpratima community development block. Within the last 7 years, capacity building in the form of concrete houses under Indira Awas Yojana, cyclone shelters, metalled roads has increased. However, in the time of disasters even the settled portions get submerged in water as the settled portions are located at a lower height than the high water level. The local demand of concrete embankments is debatable and in some places the use of brick pitching, brick block pitching, porcupine mesh and Aila bandh have not been successful in preventing breaching and consequent saltwater inundation. Vulnerability is severe in case of Basanti, Gosaba, Kultali, Namkhana, Patharpratima community development blocks and high in case of Kakdwip, Sagar and Hingalganj community development blocks (Sahana et al, 2019). This paper takes all these phenomena into account and provides certain probable mitigation strategies which include the mapping of erosion accretion sites by comparative analyses of toposheets and satellite images, site specific mangrove aforestation, improved construction of embankments following expert and local opinions, revival of the decayed creeks to prevent waterlogging at times of disaster and rehabilitation of people from sites of continuous erosion to community shelters located at elevated areas alongwith tidal river management as practiced in Bangladesh where the rivers are temporarily allowed their spill areas.

 

 
Fractal analysis and their applications in Geomorphology
Authors: Lämmle Luca , Perez Filho Archimedes , Valente Alessio , Donadio Carlo
Published: June 2022

Fractal geometry methods offer a quantitative description of complex landscapes and can effectively elucidate the behavior of fluvial and coastal geomorphological systems. The bidimensional (2D) fractal geometry of a shoreline, obtainable with Koch’s curve method, may be expressed by a fractional number between 1.1 and 1.4. In this case, the former shoreline is less rugged than the latter, which tends to a Peano’s curve with a fractal dimension D = 2, that is a plan. These sizes, under initial analysis, may not supply direct information on the main processes responsible for modeling the coast. Actually, either erosion, sediment deposition, and tectonics could generate shapes with about the same fractal dimension, independently of their intensity, age, and time during which they acted, as a result of morphological convergence. From the results of research carried out along Mediterranean-type and Brazilian coastlands, it is possible to derive, from the fractal dimension, the primary and secondary processes behind modeling. Here distinguishing tectonic events from littoral dynamics, both responsible for coastal morphology and identifying which is predominant. Calculation and comparison of the 2D-fractal analysis over time along the selected littorals are useful for assessing sea storm impacts and tsunami flash remodeling, e.g., as a relationship between dimension and energy, and the post-event shoreline resilience time comparing the fractal dimensions before and after the main events related to the morphosedimentary features. The same principles can be applied to other geomorphological systems, such as dunes, river drainage networks, islands, and lagoons, representing an important tool for understanding and classifying these environments.
Pluri-annual morphological and sedimentological changes of the Valahnúkur boulder barrier, SW Iceland
Authors: Stephan Pierre , Massé Lancelot , Dider David , Autret Ronan , Soloy Antoine , Suanez Serge
Published: June 2022

While recent studies highlighted the great mobility of boulder beaches related to the impact of storm waves, numerous researches are still needed to better understand the morphodynamic of coastal boulder accumulations. This paper provides original data about pluri-annual morphological and sedimentological changes, as well as storm-induced geomorphic processes and their impact on the Valahnúkur boulder barrier, in the south-west of Iceland. First described by Etienne & Paris (2010), this massive accumulation of boulders shows numerous evidences of coastal barrier flooding and intense boulder mobility.

Between May 2015 and May 2021, a topo-morphological survey was undertaken to analyze and quantify both cross-shore and longshore morphosedimentary processes of the Valahnúkur boulder barrier and surrounding areas. Annual campaigns of UAV (Unmanned Aerial Vehicle) flights were conducted in order to produce a set of Digital Elevation Models (DEMs) and Orthophotographs using Structure-from-Motion photogrammetry. DEMs were compared to deduce the morphological changes. Orthophotographs were analyzed from a deep learning-based method to estimate the changes in the spatial distribution of boulder sizes. Hydrodynamic conditions were reconstructed using wave buoy and tide gauge measurements. Wave runup were calibrated from the analysis of a wave/swash motion data set acquired by video monitoring related to different hydrodynamic conditions. The chronology of extreme water levels has been reconstructed on this high refective beach to estimate the elevation of the wave action during the survey period.

From the sediment budget calculation, a significant northward longshore drift of around 1000 m3/a is highlighted on the beachface. The ridge and back-barrier areas were dominated by accretion related to cross-shore boulder transport from the beach. The volume of transported boulders is highly variable according to hydrodynamic conditions. Although the morphogenic impact of winter storms is difficult to assess, the observed morphological changes suggest processes dominated by swash, overtopping and overwash. The boulder size analysis highlights a link between the boulders mass and their movement landward. Video monitoring indicates that the amplitude of the swash is quite similar whether the hydrodynamic conditions are normal or energetic. The high porosity of the barrier appears to be a key factor in the dissipation of wave energy.
Holocene evolution of coastal dunes in western France: regional reconstruction from archaeological and historical data
Authors: Gorczynska Aneta , Stephan Pierre , Pailler Yvan , Nicolas Clément , Penaud Aurélie , David Ophélie , Vidal Muriel , Le Gall Bernard
Published: June 2022

The long-term evolution of coastal sand-dune systems is is known to be controlled by variations in sediment supply, relative sea level (RSL), wind energy, vegetation cover and anthropogenic forcing. The link between episodic sand invasion and changes in climate conditions (enhanced storminess) has been previously evidenced along the Atlantic coasts of Europe from stratigraphical, geomorphological and chronological investigations of recent aeolian sand-dune deposits. While well-constrained timing templates of dune accretion during Holocene were reconstructed in Portugal, Spain and Ireland, available data about the French Atlantic coast are limited to the Aquitaine dune complex (SW France). This lack of data is mainly due to the absence of well-developed palaeosoils interbedded within the aeolian sand deposits, especially in Brittany where only thin humic layers are preserved within the coastal dune sediment sequences. An alternative approach is here applied to the coastal dunes of Brittany by also integrating available and partly revised archaeological dataset, excavated from the end of the 19th century, and used as chrono-stratigraphical markers to reconstruct at a regional scale the periods of coastal dunes mobility during the last ca. 6,000 years. This analysis was further completed with historical data about the last few centuries. 214 sites distributed along the western coasts of France have been selected to provide accurate information in terms of dune stratigraphy and chronology. A conceptual tool routinely used in archaeology, the Harris matrix, was employed to synthesise these chrono-stratigraphic data about 78 coastal sand-dune systems. Four main episodes of aeolian activity identified during the mid- to late-Holocene period are dated at 4,250-4,100 cal BP (phase 1), 3,250-2,400 cal BP (phase 2), 1,050-700 cal BP (phase 3), and 350-110 cal BP (phase 4). Despite some methodological limitations, archaeological remains appear to be relevant chronological indicators and may be used to reconstruct ancient periods of coastal dune mobility. Finally, an evolutionary model is established about the sand-dune morphological changes that occurred during the mid-to late-Holocene period along the Western France coasts, whereas the nature of the driving mechanisms of sand movement initiation is also discussed.
Effect of water level variation on the channel width in the river mouth
Authors: Nagumo Naoko , Egashira Shinji
Published: June 2022

River flow, sediment transport and channel width influence one another, and channel width generally changes toward the equilibrium state in sediment transport. When the tidal range is large with the water level fluctuating periodically, the sediment transport capacity of the river channel increases in the river mouth due to the drawdown effect during low tide, whereas the backwater effect becomes dominant during high tide. Therefore, the channel width is determined by the flow discharge during low tide and tends to be wider toward the mouth. On the other hand, when the channel in the river mouth is submerged during the rainy season in tropical regions, the channel width is defined by the flow discharge during the transition period from the rainy season to the dry season. This presentation explains a mechanism that determines the channel width in the river mouth by taking rivers in Japan and Southeast Asia as examples.
Comparison of the methods for valley bottom extraction: A case for the mountain drainage basin where colluvial and bedrock valleys dominate 
Authors: Lee Won Young , Chen Hui , Byun Jongmin
Published: June 2022

Valleys associated with convergent topography are common features on the earth’s surface. Valley bottoms along which most rivers flow have been considered geomorphologically important since stream channels adjust their forms within them and, consequently, the width of the valley bottom determines the planform and type of channel reach. The headwater streams comprise transitional and colluvial channels and account for nearly 70 to 80 percent of the river network. They play a role in the movement or retention of sediments and nutrients transferred from surrounding hillslopes, and the provision of habitats for the various aquatic and riparian organisms in mountainous regions. Thus, accurate delineation of the valley bottoms, including colluvial valley portions, is fundamental for managing mountain rivers. In this study, we applied widely used methods for extracting valley bottoms into an intermontane catchment where colluvial valleys dominate (i.e., the Huengjeong basin in South Korea), verified and compared their results to suggest a practical procedure for applying these methods to the uppermost basins in a mountainous region. We compared two methods: the Valley Confinement Algorithm (VCA) which extracts valley bottoms based on flood-prone areas estimation, and the Geomorphon-based method using geomorphic units matching with the topography of valley bottoms. Our results show that the valley bottoms delineated from the VCA with flooding factor 1, smaller than the value (i.e., 3) used for extracting downstream unconfined valley bottoms, characterize well the valley bottoms in the study area. However, the valley bottom width becomes wider where low order tributary flows over flat areas such as river terraces. For the Geomorphon-based method, it turned out that the geomorphic units based on a Geomorphon calculated using a single set of parameter values (i.e., analysis radius and flatness threshold) did not properly capture both headwater colluvial valley and downstream fluvial valleys. Therefore, we extracted valley bottoms for colluvial and fluvial valley bottoms, respectively: Colluvial valley bottoms could be delineated by a set of geomorphic units (valley, hollow, slope, and spur) based on a Geomorphon calculated using a 50 m analysis radius and 0.5-degree flatness threshold; The fluvial valley bottoms could be delineated by a set of geomorphic units (valleys, depressions, foot slopes, and flats) based on 125 m analysis radius and 5-degree flatness threshold. While choosing the geomorphic units corresponding to valley bottoms for the Geomorphon-based method is highly subjective and time-consuming, the VCA could easily detect flood-prone areas below river terraces by only adjusting flooding depth. Thus, the VCA is thought to be suitable for extracting valley bottoms from colluvial valley-dominated areas.  
Identification and mapping of beach ridges in the Acheron River delta (Western Greece)
Authors: Griva Diamantina , Karymbalis Efthimios , Poscolieri Maurizio , Parcharidis Isaak , Kapsimalis Vasilios , Tsanakas Konstantinos , Batzakis Dimitrios-Vasileios
Published: June 2022

A beach ridge is a coastal depositional landform defined as a relict shore ridge that is more or less parallel with the coastline and with other landward-adjacent ridges. It is built by wave swash that may be surmounted by wind-deposited sediments. Once such a ridge becomes isolated from daily active beach processes by coastal progradation, it becomes a beach ridge. These landforms can serve as indicators of the positions of past shorelines and relative sea-levels. The older beach ridges are located further inland, and new ones are built progressively seaward. The main aim of this study is to identify and map in detail a series of beach ridges developed and preserved at the delta of the Acheron River, in Western Greece. The part of the deltaic plain north of the main river channel is characterized by a ridge and swale topography consisting of several beach ridges, which are almost parallel to the present-day shoreline of Phanari Bay. These beach ridges have accreted rapidly and gradually filled the Phanari Bay over the last 900 years. To recognize and map the beach ridges two different methodologies have been applied. The first method is based on the application of indicators on Sentinel 2 satellite images for inverting the swales since sometimes it is difficult to discriminate the ridges themselves. The Normalized Difference Vegetation Index (NDVI), a normalized difference index that describes the difference between visible and near-infrared reflectance of vegetation cover, was used to discriminate swales based on their vegetation. In addition, the Normalized Difference Water Index (NDWI), the most suitable index for mapping water bodies, was used to separate the swales from the ridges. NDWI allowed us to detect swales using satellite images taken in the winter months since topographic depressions are covered by water during this period of the year. The second methodological approach has been performed by using a 2 m cell size Digital Elevation Model (DEM) obtained from the Hellenic Cadastre. The identification of the beach ridges was mainly based on the analysis of the DEM and the application of Red Relief Image Map, a ground surface visualization methods based on the combination of three landform element layers i.e. topographic slope, positive openness and negative openness. The two crossing methods led to the construction of a preliminary map of the beach ridge system, which was verified in the field to produce the final map. The identification and mapping of the beach ridges was the first necessary step to trace the palaeogeographic evolution as well as to reconstruct the accretion history of this part of the Acheron River delta over the last 900 years.
Neotectonic influence on a delta landscape genesis downstream the Amazon River – North Brazil
Authors: Machado Helen , Villela Fernando , Pinheiro Marcos , Cianfarra Paola
Published: June 2022

Many researchers have inferred that the genesis and formation of fluvial features at the mouth of the Amazon River (North Brazil) are related only to the sea level changes occurred in the Quaternary. In addition, there are still few works that take into account the possible influence of Neotectonics on the formation of these features, such as in the Breves-Boiuçu delta, located close to the Marajó Island, at the mouth of the Amazon River. This delta formed during the marine regression occurred around 5000 years BP, which caused silting of important rivers within the current delta feature. However, possible relations between the delta genesis and tectonic structures that have been reactivated since Miocene, as the Gurupá Arch, are still under debate. In this sense, the objective of this work is to evaluate the possible neotectonic influences on the formation of the Breves-Boiuçu delta. In order to achieve this objective, semi-automatic detection of structural lineaments was performed. Following the classical paradigm of Donald Wise, we have considered that the trend of the principal lineament domain corresponds to the main horizontal crustal stress (Shmax). Such lineaments were identified on pre-processed Shuttle Radar Topography Mission (SRTM) data, by means of the software SID3. These information were cumulated in databases and statistically analyzed by Daisy 3 software (https://host.uniroma3.it/progetti/fralab/Downloads/Daisy_Program/). In addition, drainage anomalies were mapped, considering that they are indicative of tectonic control on the river network. Finally, the possible size variation of the delta in the last 30 years was analyzed, evaluating its progradation rate through satellite images (Landsat 7 and Sentinel2). The results of the analysis of the lineament domains for the regional and local scale point to two possible tectonic models, in which it is possible to recognize the subsidiary fractures and shear fractures associated to a main regional strike-slip (R-Riedel shears, T-tension fractures, Y and X –shear fractures). According to the first model, dextral shear corridor E-W trending characterizes the investigated area with Shmax NW-SE oriented. Normal faults, joints, and T fractures follow this last orientation, whereas the structures E-W and N-S mapped correspond to, respectively, Y (dextral) and X (sinistral) faults. In the second model, a dextral shear zone NE-SW orientated exists, and E-W structures correspond to T fractures, whereas the N-S structures are dextral P faults. Regarding the drainage network analysis, several tectonic indicators were identified, such as: rectilinear drainages, elbows, and paleo-channels. Further studies are necessary to understand which tectonic model better characterizes the region, as well as the influence of neotectonic activity on the evolution of the deltaic landscape.
Mount Greco and Chiarano Valley (Central Italy): an example of geotourism in the Abruzzo, Lazio, and Molise National Park
Authors: D'Amico Daniela , Esposito Gianluca , Mancinelli Vania , Miccadei Enrico , Paglia Giorgio , Sammarone Luciano , Sulli Cinzia
Published: June 2022

Mount Greco and Chiarano Valley represent a crucial sector for enhancing the high geotourism potential of the Abruzzo, Lazio, and Molise National Park (Central Italy). This area is characterized by landscapes that strictly incorporate the relationships between geoheritage and tourism, showing how various geological-geomorphological processes have produced different features and behavior of territories. These active processes continually change the landscape and allow us to directly observe wonderful environments within their spatial and temporal scales. The study area comprises landforms resulting from a wide range of geomorphological processes: glacial landforms, karst landforms, slope landforms, fluvial and fluvio-glacial landforms. In this framework, one of the most beautiful geotourist destinations is the Pantaniello Lake’s area (1818 m a.s.l.), a natural moraine basin located in the middle of an impressive glacial valley with a small mountain lake resulting from the damming of a U-shaped valley due to a slight moraine arch. The present-day setting of the study area testifies the overlap of different geomorphological landscapes over space and time, highlighted by various types of landforms resulting from relict glacial environments, landslides, and karst processes. Finally, this work presents an example of the enhancement and promotion of geotourism in the Abruzzo, Lazio, and Molise National Park. It allows for the description of an awesome landscape within the park in an easy-to-understand way through thematic maps, visual legends, and cartoons. This kind of approach can increase people's knowledge and make them aware that the present-day landscape results from a long-term dynamic evolution providing outstanding landscapes, but also intrinsic natural hazards and risks.
Pixel-based coastal change detection
Authors: Collings Benedict , Ford Murray , Dickson Mark
Published: June 2022

Satellite earth observation data has been frequently applied to monitor shoreline change at very large geographic scales. Techniques focus on the extraction of the instantaneous waterline boundary, a shoreline proxy that can be extracted from publicly available multispectral satellite data with sub-pixel accuracy. Interpreting coastal change through this proxy can be uncertain as the position of the waterline is dynamic, a function of beach gradient and constantly fluctuating marine processes, and might not capture information of the full spectrum of drivers influencing change for a given section of coast.

Satellite data is acquired in raster format and there is useful information stored in each pixel across the entire coastal zone. Applying per-pixel change detection techniques could offer further insights to the role of drivers of coastal change beyond a vectorised land-water boundary. This paper describes a new method for monitoring coastal change at large geographic scales with public satellite remote sensing data through pixel-based change detection. The first step is the classification of pixels into specific coastal landcover classes. This is challenging at large scales owing to complex and diverse physical environmental characteristics. A methodology was developed and applied to New Zealand’s coastline, identifying 9 landcover types including sedimentary coast. A combination of Sentinel multispectral and synthetic-aperture-radar data were used to derive composite imagery for 2019 using Google Earth Engine cloud computing platform. This was classified using a set of hierarchal rules and machine learning in a Python programming environment. This was validated nationally against high-resolution aerial photography and commercial satellite imagery. This produced a coastal specific landcover classification from which per-pixel change detection techniques can be applied. Overall accuracy was 86.38% and exceeded 90% when normalised by class area.

The outputs and code are available, and the framework has been designed to work with a range of earth observation datasets and can be applied to other regions around the world. Ongoing work includes implementing a framework to assess long-term change, at the coast in New Zealand. By investigating how specific coastal landcover types are changing, useful information can be acquired to better interpret drivers of coastal change and the impacts on coastal geomorphology at large geographic scales.

 

Keywords: Satellite Remote Sensing, Multispectral, Synthetic Aperture Radar, Landcover classification, Change detection, Coastal change.
Hurricane Storm Surge Sedimentation on McFaddin National Wildlife Refuge, Texas: Spatial Variations in Sediment Distribution in the Right-Front Quadrant of Hurricane Ike
Authors: Hodge Joshua
Published: June 2022

This study investigates spatial variations in sediment distribution in the right-front quadrant of Hurricane Ike, on McFaddin National Wildlife Refuge on the East Texas Gulf Coast. The purpose of this study was to discover how hurricane storm surge sedimentation spatially varies in relation to the landfall location of Hurricane Ike. Fieldwork conducted in 2017-2018 involved digging shallow pits on four coastal marsh transects between Sabine Pass, Texas and High Island, Texas. The transects extend 880-1630 meters, with pit sites beginning near the coastline and extending landward. Results obtained in the field indicate that the Hurricane Ike sediment deposit has been found on all four transects, and that the deposit decreases in thickness moving landward along each transect. Furthermore, the observational results of this study were used in Regression Analyses to model sediment thickness based on pit site distance inland, pit site elevation, and distance from the landfall location of Hurricane Ike. Results indicate that the distance from landfall location was not a significant predictor of deposit thickness, which is very likely due to all four transects being in the right-front quadrant of landfalling Hurricane Ike. The findings of this study provide improved understanding of the spatial relationship between storm surge sedimentation and storm surge heights, valuable knowledge about the sedimentary response of coastal marshes subject to storm surge deposition, and useful guidance to public policy aimed at combating the effects of sea-level rise on coastal marshes along the northern Gulf of Mexico coastline. 