Decadal sediment dynamics of a perturbed fluvial system: the case of the man-made Marecchia River canyon, Northern Apennines 

2021 ◽  
Author(s):  
Manel Llena ◽  
Tommaso Simonelli ◽  
Francesco Brardinoni
Keyword(s):  
Fluvial Erosion ◽  
Gravel Mining ◽  
River Incision ◽  
Fluvial Incision ◽  
River Stretch ◽  
Downstream Effects ◽  
Digital Elevation ◽  
Management Plans ◽  
Sediment Transfer ◽  
Active Channel

<p>River canyons are transient geomorphic systems shaped by river incision into bedrock and coupled by instability of the adjacent valley walls. Investigating the evolution of river canyons is typically challenging due to the geologic time scales involved. In this context, the Marecchia River, which hosts in its intermediate portion a 6-km canyon, developed since the early 1950’s following intense gravel mining, may be instructive. Indeed, this setting offers the opportunity to: (i) document canyon development through highly erodible pelitic rocks; and (ii) evaluate relevant upstream and downstream effects on fluvial morphodynamics. To these ends, we subdivide the 50-km stretch of the Marecchia River main stem into 22 homogeneous reaches and evaluate decadal geomorphic changes through analysis of LiDAR-derived digital elevation models (i.e., 2009 and 2019) in conjunction with planimetric changes of active channel width delineated on orthophoto-mosaics (i.e., 2009, 2012, 2014, 2017, 2019). The estimation of patterns and rates of fluvial erosion into bedrock and its geomorphic effects are essential for understanding landscape evolution and for applying sustainable sediment management plans.</p><p>In terms of volumetric changes, the entire river stretch recorded a decadal degradation of 2,516,150 m<sup>3</sup> (57%) and 1,884,700 m<sup>3</sup> of aggradation (43%), with a corresponding net volume loss of -631,450 m<sup>3</sup>. Highest specific volumes of aggradation were observed in a homogeneous reach located in the lower part of the study segment (0.5 m<sup>3</sup>/m<sup>2</sup>), while highest values of degradation were observed in the upper reach of the canyon (-2.3 m<sup>3</sup>/m<sup>2</sup>). During the 2009-2019 period, knickpoint headward migration within the canyon has progressed for approximately 500 m, producing an average bedrock incision of about 10 m. As documented by area and volume changes, both rates of fluvial incision and canyon widening, as modulated by landslide activity and valley wall collapses, are highest in proximity of the main knickpoint and tend to decrease progressively downstream. By March 2019, when the second LiDAR survey was conducted, the main knickpoint had reached the foundations of a major check dam, which eventually collapsed two months later. Upstream of the canyon, channel reaches displayed narrowing dynamics with an alternation of degradation and aggradation processes. In terms of total volumetric changes, these reaches presented an indirect correlation with confinement, with the most confined reaches acting as sediment transfer zones. In contrast, the segment downstream of the canyon displayed widening dynamics (+ 11 m on average) together with an increase of aggradation processes. Due to the pelitic nature of the hosting bedrock, despite the high geomorphic change observed, most of the material supplied by the canyon walls gets transported in suspension, contributing very little to the estimated budget of the Marecchia River's distalmost reaches. In this way, we argue that most part of the aggradation observed in this segment was originated upstream, bypassing the canyon.</p>

Climatic and tectonic controls on strath terraces along the upper Weihe River in central China

2016 ◽  
Vol 86 (3) ◽  
pp. 326-334 ◽  
Author(s):  
Hongshan Gao ◽  
Zongmeng Li ◽  
Yapeng Ji ◽  
Baotian Pan ◽  
Xiaofeng Liu
Keyword(s):  
Yellow River ◽  
Central China ◽  
Fluvial Deposits ◽  
The Past ◽  
River Incision ◽  
System A ◽  
Fluvial Incision ◽  
Quaternary Climate ◽  
Field Investigations ◽  
Weihe River

AbstractThe Weihe River in central China is the largest tributary of the Yellow River and contains a well-developed strath terrace system. A new chronology for the past 1.11 Ma for a spectacular flight of strath terraces along the upper Weihe River near Longxi is defined based on field investigations of loess—paleosol sequences and magnetostratigraphy. All the strath terraces are strikingly similar, having several meters of paleosols that have developed directly on top of fluvial deposits located on the terrace treads. This suggests that the abandonment of each strath terrace by river incision occurred during the transition from glacial to interglacial climates. The average fluvial incision rates during 1.11—0.71 Ma and since 0.13 Ma are 0.35 and 0.32 m/ka, respectively. These incision rates are considerably higher than the average incision rate of 0.16 m/km for the intervening period between 0.71 and 0.13 Ma. Over all our results suggest that cyclic Quaternary climate change has been the main driving factor for strath terrace formation with enhanced episodic uplift.

scholarly journals Remote-sensing science and technology for studying glacier processes in high Asia

2000 ◽  
Vol 31 ◽  
pp. 164-170 ◽  
Author(s):  
Michael P. Bishop ◽  
Jeffrey S. Kargel ◽  
Hugh H. Kieffer ◽  
David J. MacKinnon ◽  
Bruce H. Raup ◽  
...  
Keyword(s):  
Image Data ◽  
Stereo Image ◽  
Accurate Information ◽  
Glacier Mass Balance ◽  
Digital Elevation ◽  
High Asia ◽  
Global Land ◽  
Space Project ◽  
Sediment Transfer ◽  
Elevation Model

AbstractA large number of multispectral and stereo-image data are expected to become available as part of the Global Land Ice Measurements from Space project. We investigate digital elevation model extraction, anisotropic reflectance correction and selected glacier analysis tasks that must be developed to achieve full utility of these new data. Results indicate that glaciers in the Karakoram and Nanga Parbat Himalaya, northern Pakistan, exhibit unique spectral, spatial and geomorphometric patterns that can be exploited by various models and algorithms to produce accurate information regarding glacier extent, supraglacial features and glacier geomorphology The integration of spectral, spatial and geomorphometric features, coupled with approaches for advanced pattern recognition, can help geoscientists study glacier mass balance, glacier erosion, sediment-transfer efficiency and landscape evolution.

BEDFLOW: integrating river morphodynamics in the Sillaro River across spatial and temporal scales

2020 ◽  
Author(s):  
Francesco Brardinoni ◽  
Anna Rita Bernardi ◽  
Federico Bonazzi ◽  
Giuseppe Caputo ◽  
Marwan Hassan ◽  
...  
Keyword(s):  
Vertical Channel ◽  
Channel Width ◽  
Topographic Maps ◽  
Event Scale ◽  
Channel Changes ◽  
Spatial And Temporal Scales ◽  
Gravel Mining ◽  
Basin Scale ◽  
Channel Slope ◽  
Active Channel

<p>Anthropogenic disturbance is one of the main drivers of contemporary river adjustment. In mountain streams, information and prior work on post-disturbance recovery rates is limited, compared to lowland counterparts. The BEDFLOW initiative aims to investigate fluvial morphodynamics along the mountain portion of the Sillaro River (138 km<sup>2</sup>), Northern Apennines, to guide local strategies of sediment management at the basin scale and improve environmental quality of this fluvial system. Of particular interest is the understanding of the historical and contemporary response of the Sillaro River to gravel mining activities, which focused in the mid-to-lower portions of the river between the mid-1940s and the early 1980s. To this end, BEDFLOW adopts a multi-scale approach that integrates: (1) historical analysis of planform channel changes across the entire montane channel main stem over the past 100 years; (2) hydraulic and bed texture characterization of 14 representative reaches that encompass drainage areas comprised between 2.7 and 113 km<sup>2</sup>; and (3) flood-event scale, RFID bedload monitoring in two reaches, complemented by topo-photogrammetric surveys of the subaerial and submerged channel bed.</p><p>Analysis of historical channel changes was conducted by mapping active channel width on historical topographic maps (1928) and across 11 sequential aerial photo sets (1954, 1969, 1976, 1988, 1996, 2000, 2008, 2011, 2014, 2016 and 2018), along a valley segment of about 26 kilometers (i.e., 35 homogeneous reaches). Vertical channel adjustment was assessed by comparison of long profiles extracted from 1928 and 1976 topographic maps.</p><p>Preliminary results indicate that the river has experienced intense channel narrowing between 1969 and 1996. This pattern has progressively slowed down, even though narrowing continues until today. Cumulatively, reduction in active channel width has been highest in the distal most unconfined reaches, where median width has decreased from >120 m in 1954 to about 20 m in 2018, intermediate in semi-confined reaches (from 99 m to 28 m), and least in the upper confined reaches (from 30 m to 15 m). In the semi-confined and unconfined reaches, where most of the gravel mining took place, channel pattern has changed from braided to wandering and/or from wandering to single-thread. Today, after about 35 years since in-channel gravel mining became interdicted, the river still exhibits signs of incomplete recovery, as bedrock sporadically outcrops amidst mid channel bars, formerly occupied by braided plains.</p><p>The two monitoring reaches, which are active since February 2020, have contrasting morphology and degree of hillslope coupling. The upper one (drainage area = 35 km<sup>2</sup>) is a riffle-pool, uncoupled reach, characterized by a fine-to-coarse gravel texture and a channel slope of 0.8 %. The lower one (50 km<sup>2</sup>) is a transitional reach with dominantly plane-bed morphology and lesser riffle-pool and step-pool stretches; it is characterized by fine gravel to boulder texture, and by a channel slope of 1.5 %. The b-axis of deployed tracer stones spans from 36 to 180 mm.</p><p>The Sillaro River basin functions also as a training site for students. This work, as part of the projects BEDFLOW and BEFLOW PLUS, is partially funded by Fondazione Cassa di Risparmio in Bologna.</p><p>https://site.unibo.it/bedflow/en</p><p>https://site.unibo.it/bedflow/it</p>

Migrating divides induce drainage reversal toward cliffs and escarpments

2020 ◽  
Author(s):  
Liran Goren ◽  
Elhanan Harel ◽  
Eitan Shelef ◽  
Hanan Ginat
Keyword(s):  
Initial Conditions ◽  
Plate Boundary ◽  
Independent Evidence ◽  
Valley Fill ◽  
Fluvial Incision ◽  
Geological Conditions ◽  
Geodynamic Models ◽  
Hillslope Processes ◽  
Active Channel ◽  
Reversed Segment

<p>Observations from around the globe show that drainage reversal toward cliffs (and at a larger scale, toward escarpments) is a common phenomenon.  Drainage reversal occurs when a channel that used to grade in one direction reverses its gradient while exploiting its antecedent valley, forming barbed tributaries with junction angle >90°. Drainage reversal is an important end-member of fluvial reorganization that drastically shifts the hydrologic and geomorphic functionality of the landscape.  The processes that induce drainage reversals, however, remain largely enigmatic. In many cases, tectonic or structural tilt of the surface is invoked to explain reversal toward the tilt direction, but independent evidence for tilting is rare. Moreover, in great escarpments, geodynamic models predict tilting away from the escarpment, opposite to the sense of reversal discussed here.</p><p>We study drainage reversals toward the southern Arava Valley escarpment in Israel, along the Sinai-Arabia transtentional plate boundary. In this area, we establish reversals by observations of barbed tributaries, valley-confined windgaps, and terraces and interfluves that grade opposite to the grading direction of the active channel. Detailed morphological and geological analysis of the field area gives rise to a new, tilting independent mechanism for drainage reversal toward cliffs. The initial condition for this mechanism is a cliff that truncates fluvial channels that flow over the highland and away from the cliff, and a water divide that coincides with the cliff. The truncated channels appear as saddles along the cliff and are commonly filled with alluvial and colluvial sediments. Such initial conditions characterize shoulder-type great escarpments and cliffs that form following river capture events. Importantly, in these settings, the sediments that fill the truncated channels are more erodible than the bedrock that builds the interfluves.</p><p>According to the mechanism we propose, the erodible valley fill near the steep cliff is initially transported down the cliff via hillslope processes, which results in a gradual migration of the divide along the antecedent valley and away from the cliff. A reversed channel segment forms between the receding divide and the cliff, such that along the channel, the divide and the cliff are not coincident anymore. The faster fluvial incision in the reversed segment with respect to the antecedent channel further pushes the divide away from the cliff. When the receding divide traverses a tributary confluence, a barbed tributary forms. The increased discharge of the reversed segment facilitates cliff embayment that eventually affects cliff retreat and morphology.</p><p>This new mechanism indicates that a relatively thin layer of erodible valley fill could be a tipping point that completely changes the trajectory of landscape evolution via drainage reversal. Importantly, however, flow reversal towards cliffs does not necessitate such a layer but instead could be triggered by other hydrological and geological conditions that promote faster erosion toward the cliff within the antecedent channel with respect to the interfluves. </p>

scholarly journals The effects of in-stream gravel mining on river incision: an example from Central Adriatic Italy

2015 ◽  
Vol 59 (2) ◽  
pp. 95-107 ◽  
Author(s):  
Domenico Aringoli ◽  
Marcello Buccolini ◽  
Laura Coco ◽  
Francesco Dramis ◽  
Piero Farabollini ◽  
...  
Keyword(s):  
Gravel Mining ◽  
River Incision

scholarly journals A Novel Hybrid Model for Developing Groundwater Potentiality Model Using High Resolution Digital Elevation Model (DEM) Derived Factors

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2632
Author(s):  
Javed Mallick ◽  
Swapan Talukdar ◽  
Nabil Ben Kahla ◽  
Mohd. Ahmed ◽  
Majed Alsubih ◽  
...  
Keyword(s):  
Feature Selection ◽  
High Resolution ◽  
Hybrid Model ◽  
Groundwater Potential ◽  
The Novel ◽  
Receiver Operating Characteristic Curves ◽  
Digital Elevation ◽  
Management Plans ◽  
Fuzzy Feature Selection ◽  
Elevation Model

The present work aims to build a unique hybrid model by combining six fuzzy operator feature selection-based techniques with logistic regression (LR) for producing groundwater potential models (GPMs) utilising high resolution DEM-derived parameters in Saudi Arabia’s Bisha area. The current work focuses exclusively on the influence of DEM-derived parameters on GPMs modelling, without considering other variables. AND, OR, GAMMA 0.75, GAMMA 0.8, GAMMA 0.85, and GAMMA 0.9 are six hybrid models based on fuzzy feature selection. The GPMs were validated by using empirical and binormal receiver operating characteristic curves (ROC). An RF-based sensitivity analysis was performed in order to examine the influence of GPM settings. Six hybrid algorithms and one unique hybrid model have predicted 1835–2149 km2 as very high and 3235–4585 km2 as high groundwater potential regions. The AND model (ROCe-AUC: 0.81; ROCb-AUC: 0.804) outperformed the other models based on ROC’s area under curve (AUC). A novel hybrid model was constructed by combining six GPMs (considering as variables) with the LR model. The AUC of ROCe and ROCb revealed that the novel hybrid model outperformed existing fuzzy-based GPMs (ROCe: 0.866; ROCb: 0.892). With DEM-derived parameters, the present work will help to improve the effectiveness of GPMs for developing sustainable groundwater management plans.

scholarly journals Las capturas fluviales: contextos, causas y consecuencias. Una explicación de los procesos de captura fluvial en distintos contextos geológicos

Espacios ◽  
2017 ◽  
Vol 3 (5) ◽  
pp. 27
Author(s):  
Alvar Pastor
Keyword(s):  
Fluvial Erosion ◽  
Fluvial Incision ◽  
Palabras Clave ◽  
La Red

<p>La red de drenaje fluvial está en continua reorganización a una escala de tiempo geológico. En ciertos contextos, esta reorganización está fuertemente controlada por capturas fluviales que producen la desviación de flujos de agua desde un cauce hacia otro. Por tanto, las capturas fluviales pueden influenciar en la distribución territorial del agua y de los sedimentos asociados. Este artículo de revisión pretende proveer una visión global sobre las capturas fluviales, explicando el fenómeno y descifrando sus causas. Partiendo de la idea de que la ocurrencia de capturas fluviales está relacionada con la diferencia entre la velocidad de incisión vertical de cada uno de los cauces implicados, en este manuscrito se analizan los distintos tipos de capturas fluviales vinculados a diversos contextos geológicos y se relaciona cada caso con la alteración de alguno de los parámetros que controlan la capacidad de incisión de los cauces (el área de drenaje, la pendiente del cauce, la erodabilidad del lecho, y la carga de sedimentos transportada). Finalmente, se discute por qué es importante el estudio de las capturas fluviales y se muestra cómo algunas capturas fluviales pueden afectar a los intereses humanos.</p><p><strong>PALABRAS CLAVE:</strong> red de drenaje, captura fluvial, incisión fluvial, erosión remontante.</p>

scholarly journals River Incision in Relation to Post-Glacial Events in the Humber River Basin, Ontario

2006 ◽  
Vol 59 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Roger T.J. Phillips ◽  
André Robert
Keyword(s):  
River Basin ◽  
Drainage Basin ◽  
Plan View ◽  
River Incision ◽  
Digital Elevation ◽  
Humber River ◽  
Late Wisconsinan ◽  
Valley Incision ◽  
River Valleys ◽  
River Drainage Basin

Abstract River valleys in the Humber River drainage basin have derived most of their morphology from processes occurring over the last 13 000 14C BP. Some of the valley reaches possess very distinct characteristics in terms of plan-view morphology, such as valley meandering and loop features along the valley sides. In this study, the valley morphology and stratigraphy of the upper Humber River basin are examined in order to assess the character of post-glacial valley evolution. Existing knowledge of late Wisconsinan and Holocene events has been considered to place this valley evolution into a regional context. Radiocarbon dating and digital elevation models suggest that the majority of valley incision occurred during or soon after regional deglaciation. Looping valley features and terrace patterns indicate that most valley morphology can be attributed to larger ancestral rivers. Although direct melt-water contributions are expected due to deglaciation, it is suggested that other processes due to the climatic and hydrogeologic effects of fluctuating proglacial lake levels also played a role.

Evolution of Quaternary cave levels in low-relief karst regions: influence of fluvial incision and speleoinception of chalk caves in northern France

2020 ◽  
Author(s):  
Daniel Ballesteros ◽  
Carole Nehme ◽  
Andrew Farrant ◽  
Dominique Todisco ◽  
Diana Sahy ◽  
...  
Keyword(s):  
Laminated Sediments ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Northern France ◽  
Base Level ◽  
River Terraces ◽  
River Incision ◽  
Fluvial Incision ◽  
Relevant Role ◽  
Conduit Development

&lt;p&gt;In many lowland areas, fluvial incision is usually relatively slowly and another factors as the stratigraphical control would play a relevant role. In the lower Seine valley of Northern France, cave systems developed in the sub-horizontal Upper Cretaceous chalk of the Anglo-Paris Basin offer the potential to constrain the Quaternary evolution of the Seine valley and to test the role of speleo-inception theory of conduit development in the chalk aquifer. Six chalk caves, with a combined length of over 5.7 km were studied in detail. In each studied cave, data on the passage morphology, cave deposits (speleothem and sediments) and stratigraphical control were recorded. Cave levels were defined based on geomorphological evidence and altitudinal cave passage analyses. The chronology of cave development and abandonment was constrained by ten U-Th speleothem dates and 144 palaeomagnetic samples collected from laminated sediments within the caves. Four regional cave levels were identified at 10, 40, 75-80, and 85-90 m asl, showing 1% slope to the Seine estuary. Each cave level is formed by phreatic and epiphreatic conduits enlarged by paragenesis, showing branch work or maze patterns. Cave infill corresponds mainly to clayey to silty sediments that occupy the majority of the karst conduits. Locally, sands and pebbles occur, and speleothems are relatively scarce. Palaeomagnetic and U-Th data show that these cave levels developed sequentially from &gt;1.06 ka to c. 300 ka, ca. 78% of them in relation to prominent Turonian, Coniacian and Santonian hardgrounds as well as sheet- and semi-tabular flint bands. Their age correlates with the estimated age of the lower river terraces from limited previously published OSL, palaeontological and U-Th dating, although new age data from the study cave improve the chronology of the higher-level river terraces. The combination of all this data suggests an initial slow rate of incision during the early Pleistocene, followed by a phase of more rapid river incision up to ~ 0.30 m&amp;#183;ka&lt;sup&gt;-1&lt;/sup&gt; from ca. 1 to 0.7 Ma. Later, incision rates dropped to ~0.08 m&amp;#183;ka&lt;sup&gt;-1&lt;/sup&gt; during Middle Pleistocene, and 0.05 m&amp;#183;ka&lt;sup&gt;-1&lt;/sup&gt; since the beginning of the Upper Pleistocene. In conclusion, fluvial incision constitutes also a relevant speleogenic factor in low-gradient areas as the Seine Basin, where conduit development was favoured at sites where suitable lithological inception horizons intercept the contemporary base level.&lt;/p&gt;

The role of the Nahr Menashe in the Messinian Salinity Crisis: formation, dissolution and fluvial incision of the top evaporite unit in the NE Levant Basin, Eastern Mediterranean

2021 ◽  
Author(s):  
SM Mainul Kabir ◽  
David Iacopini ◽  
Adrian Hartley ◽  
Vittorio Maselli ◽  
Davide Oppo
Keyword(s):  
Eastern Mediterranean ◽  
Messinian Salinity Crisis ◽  
3D Seismic ◽  
Fluvial Erosion ◽  
Base Level ◽  
Fluvial Incision ◽  
Formation And Evolution ◽  
New Interpretation ◽  
Levant Basin

&lt;p&gt;The Nahr Menashe Unit (NMU), which forms the uppermost part of the Messinian succession, &amp;#160;is one of the most cryptic and elusive sedimentary units present in the Levant basin (Eastern Mediterranean). We use a high-resolution 3D seismic dataset from offshore Lebanon to propose a new interpretation for its formation and evolution. The NMU varies laterally across the basin both in thickness and internal seismic characteristics. The variably coherent cyclic seismic packages affected by fracturing, faulting suggests that the NMU represent a reworked, layered evaporite succession interbedded with siliciclastics derived from both the Lebanon Highlands and the Latakia Ridge. Widespread semi-circular depressions, random linear imprints, passive surface collapsing and residual mound features within the NMU suggest that post depositional diagenetic and/or strong dissolution process often affected its evaporite-rich subunits. The well-known extended valley and tributary channel systems characterising the uppermost NMU shows mainly erosional rather than depositional features. Erosion started after deposition of NMU as a consequence of the maximum base level fall during the last phase of the Messinian Salinity Crisis (MSC). The channel and valley system were subsequently infilled by layered sediments here interpreted to represent post-MSC deep water marine reflooding. In conclusion, our analyses suggest the NMU can be interpreted as a mixed evaporite-siliciclastic system deposited in a shallow marine or marginal environment, which subsequently experienced fluvial erosion and later burial by transgressive/high-stand sediments.&lt;/p&gt;

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