scholarly journals Towards an increase of flash-flood geomorphic effects due to gravel mining and ground subsidence in Nogalte stream (SE Spain, Murcia)

2016 ◽  
Author(s):  
Jose A. Ortega-Becerril ◽  
Guillermina Garzón ◽  
Marta Béjar-Pizarro ◽  
Jose Jesús Martínez-Díaz
Keyword(s):  
Flash Flood ◽  
Time Lag ◽  
Alluvial Fan ◽  
Ground Subsidence ◽  
Stream Power ◽  
Fluvial Systems ◽  
Base Level ◽  
Gravel Mining ◽  
Collateral Effects ◽  
Aquifer Overexploitation

Abstract. Transition from endorheic alluvial fan environments to well-channelized fluvial systems in natural conditions may occur in response to base-level fluctuations. However, human-induced changes in semi-arid regions can also be responsible for similar unforeseen modifications. Our results confirm that in-channel gravel mining and aquifer overexploitation over the last 50 years in the case study area have changed the natural stability of the Nogalte stream and, as a result, its geomorphic parameters including channel depth and longitudinal profile have begun to adapt to the new situation. Using interferometric synthetic aperture radar (InSAR) data we obtain maximum values for ground subsidence in the Upper Guadalentín basin of ~ 10 cm yr−1 for the period 2003–2010. In this context of a lowered base level, the river is changing its natural flood model to a more energetic one. A comparison of the 1973 flood event, the most dramatic ever recorded in the area, with the 2012 event, where there was a similar discharge but a sediment load deficit, reveals greater changes and a new flooding pattern and extension. In-channel gravel mining may be responsible for significant local changes in channel incision and profile. This, together with the collateral effects of aquifer overexploitation, can favor increased river velocity and stream power, which intensify the consequences of the flooding. The results obtained here clearly demonstrate an existing transition from the former alluvial pattern to a confined fluvial trend, which may become more pronounced in the future due to the time-lag between the drop in aquifer level and ground subsidence, and introduce a new scenario to be taken into consideration in future natural hazard planning in this area.

scholarly journals Towards an increase of flash flood geomorphic effects due to gravel mining and ground subsidence in Nogalte stream (Murcia, SE Spain)

2016 ◽  
Vol 16 (10) ◽  
pp. 2273-2286 ◽  
Author(s):  
Jose Antonio Ortega-Becerril ◽  
Guillermina Garzón ◽  
Marta Béjar-Pizarro ◽  
Jose Jesús Martínez-Díaz
Keyword(s):  
Flash Flood ◽  
Time Lag ◽  
Alluvial Fan ◽  
Ground Subsidence ◽  
Flood Event ◽  
Stream Power ◽  
Base Level ◽  
Gravel Mining ◽  
Collateral Effects ◽  
Aquifer Overexploitation

Abstract. Transition from endorheic alluvial fan environments to well-channelized fluvial systems in natural conditions may occur in response to base-level fluctuations. However, human-induced changes in semi-arid regions can also be responsible for similar unforeseen modifications. Our results confirm that in-channel gravel mining and aquifer overexploitation over the last 50 years in the case study area have changed the natural stability of the Nogalte stream and, as a result, its geomorphic parameters including channel depth and longitudinal profile have begun to adapt to the new situation. Using interferometric synthetic aperture radar (InSAR) data we obtain maximum values for ground subsidence in the Upper Guadalentín Basin of  ∼ 10 cm yr−1 for the period 2003–2010. In this context of a lowered base level, the river is changing its natural flood model to a more powerful one. A comparison of the 1973 flood event, the most dramatic flood event ever recorded in the area, with the 2012 event, where there was a similar discharge but a sediment load deficit, reveals greater changes and a new flooding pattern and extension. In-channel gravel mining may be responsible for significant local changes in channel incision and profile. This, together with the collateral effects of aquifer overexploitation, can favour increased river velocity and stream power, which intensify the consequences of the flooding. The results obtained here clearly demonstrate an existing transition from the former alluvial pattern to a confined fluvial trend, which may become more pronounced in the future due to the time lag between the drop in aquifer level and ground subsidence, and introduce a new scenario to be taken into consideration in future natural hazard planning in this area.

scholarly journals A chronology of alluvial fan response to Late Quaternary sea level and climate change, Crete

2016 ◽  
Vol 86 (2) ◽  
pp. 170-183 ◽  
Author(s):  
Richard J.J. Pope ◽  
Ian Candy ◽  
Emmanuel Skourtsos
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Alluvial Fan ◽  
Glacial Cycle ◽  
Last Interglacial ◽  
Climatic Forcing ◽  
Vegetation Development ◽  
Fluvial Systems ◽  
Transfer Rates ◽  
Base Level

AbstractTo better understand how fluvial systems respond to late Quaternary climatic forcing OSL and U-series dating was applied to stratigraphically significant sedimentary units within a small (<6.5 km2) alluvial fan system (the Sphakia fan) in southwest Crete. The resultant chronology (comprising 32 OSL and U-series ages) makes Sphakia fan one of the best dated systems in the Mediterranean and suggests that Cretan fans responded to climate in two ways. First, during the transitions between Marine Isotope Stage (MIS) 5a/4 and MIS 2/1 Sphakia fan was characterised by significant entrenchment and distal shift in the zone of deposition. It is proposed that the phases of entrenchment were driven by sea level induced base level fall during MIS 5a/4 and landscape stabilisation during the onset of the current interglacial (MIS 2/1). Second, with the exception of these two entrenchment episodes fan alluviation occurred across the entire last interglacial/glacial cycle in all climatic settings i.e. interglacials, interstadials and stadials. It is likely that the topographic setting of the catchment supplying sediment to Sphakia fan maintained high sediment transfer rates during most climatic settings enabling fan aggradation to occur except during major climatic driven transitions i.e. major sea level fall and postglacial vegetation development.

scholarly journals Recent human impacts and change in dynamics and morphology of ephemeral rivers

2013 ◽  
Vol 1 (2) ◽  
pp. 917-956 ◽  
Author(s):  
J. A. Ortega ◽  
L. Razola ◽  
G. Garzón
Keyword(s):  
Flash Flood ◽  
Human Impacts ◽  
Morphological Changes ◽  
Flood Event ◽  
Stream Power ◽  
Fluvial Systems ◽  
Before And After ◽  
Ephemeral Rivers ◽  
Natural Dynamics ◽  
Channel Patterns

Abstract. Ephemeral streams induce flash-flood events which cause dramatic morphological changes and impacts on population, due the intermittent activity of these fluvial systems. Human pressure changes the fluvial environment and so enhances the effects of natural dynamics. Local human-induced modifications can be latent over long periods of time. These changes can be studied after the flood event, to quantify their effects and detect which are most harmful. In this paper we study flash-flood effects at two sites in Spain and compare the results before and after a~flood event. Erosion is associated with areas where there have been more anthropogenic changes in floodplains and channels. Deposition is related to erosional processes in the watershed and to the tributaries. Disruption of river channel patterns changes connectivity and scouring appears due to energy excess. This excess tends to concentrate at weak points downstream produced by anthropic disturbances. Riparian vegetation is an energy sink and reaches with more cover show less erosion than those with deforestation. Infrastructures perpendicular to the direction of flow increase stream power, but peaks of erosion on the floodplain appear displaced downstream. It is important to detect human changes by analysis of hydraulic variables before the occurrence of an extraordinary event in order to anticipate catastrophic consequences resulting from inappropriate fluvial management.

Early history of the Midcontinent Rift inferred from geochemistry and sedimentology of the Mesoproterozoic Osler Group, northwestern Ontario

2007 ◽  
Vol 44 (3) ◽  
pp. 389-412 ◽  
Author(s):  
Pete Hollings ◽  
Philip Fralick ◽  
Brian Cousens
Keyword(s):  
Alluvial Fan ◽  
Midcontinent Rift ◽  
Fluvial Systems ◽  
The North ◽  
Northwestern Ontario ◽  
History Of ◽  
Group A ◽  
South Axis ◽  
Island Basalt ◽  
East West

The Mesoproterozoic 1108–1105 Ma Osler Group, a 3 km thick succession of basaltic flows and sedimentary units on the north shore of Lake Superior, is among the oldest expressions of the Midcontinent Rift. Basal sediments of the Simpson Island Formation (new name) deposited by braided fluvial systems record westward transport of debris eroded from local Archean and Proterozoic rock units. Strata deposited by this fluvial system are intercalated with, and overlain by, ocean-island basalt (OIB)-like basalts, which become increasingly contaminated up section (εNd(1100Ma) = +0.3 to –5.3). The light rare-earth element (LREE) enriched (La/Smn = 1.5–3.9) and heavy REE (HREE) fractionated (Gd/Ybn = 1.5–3.7) subaerial flows are divisible into two units that correlate with other sections of the Osler Group to the east, but simple correlations with more distant sequences are difficult. The volcanic rock dominated portion of the succession is overlain by a thin (25 m thick) conglomerate–sandstone assemblage representing southeast progradation of an alluvial fan in a semi-arid climatic setting. Clast lithologies and geochemistry indicate no extra-rift detritus was delivered from the hinterland of the fan. Various lines of evidence in both volcanic and sedimentary rocks support a scenario where early, pre-1108 Ma, subsidence along a north–south axis from the western arm of the rift to the Nipigon Embayment was replaced by subsidence along the east–west rift axis between 1108 and 1105 Ma.

Evaluating the effect of variable lithologies on rates of knickpoint migration in the Wutach catchment, southern Germany

2020 ◽  
Author(s):  
Andreas Ludwig ◽  
Wolfgang Schwanghart ◽  
Florian Kober ◽  
Angela Landgraf
Keyword(s):  
Transient Response ◽  
Stream Power ◽  
Main Trunk ◽  
Southern Germany ◽  
Level Change ◽  
Base Level ◽  
Bulk Parameter ◽  
River Profiles ◽  
Topographic Evolution ◽  
Headward Erosion

&lt;p&gt;The topographic evolution of landscapes strongly depends on the resistance of bedrock to erosion. Detachment-limited fluvial landscapes are commonly analyzed and modelled with the stream power incision model (SPIM) which parametrizes erosional efficiency by the bulk parameter K whose value is largely determined by bedrock erodibility. Inversion of the SPIM using longitudinal river profiles enables resolving values of K if histories of rock-uplift or base level change are known. Here, we present an approach to estimate K-values for the Wutach catchment, southern Germany. The catchment is a prominent example of river piracy that occurred ~18 ka ago as response to headward erosion of a tributary to the Rhine. Base level fall of up to 170 m triggered a wave of upstream migrating knickpoints that represent markers for the transient response of the landscape. Knickpoint migration along the main trunk stream and its tributaries passed different lithological settings, which allows us to estimate K for crystalline and sedimentary bedrock units of variable erodibility.&lt;/p&gt;

scholarly journals Remote Predictive Mapping 5. Using a Lidar Derived DEM to Test the Influence of Variable Overburden Thickness and Bedrock on Drainage and Basin Morphology

2014 ◽  
Vol 41 (1) ◽  
pp. 89
Author(s):  
Tim L. Webster ◽  
John C. Gosse ◽  
Ian Spooner ◽  
J. Brendan Murphy
Keyword(s):  
Land Surface ◽  
Overland Flow ◽  
Stream Power ◽  
Eastern Canada ◽  
Stream Discharge ◽  
Base Level ◽  
Overburden Thickness ◽  
Basin Morphology ◽  
Elevation Model ◽  
The Impact

A 4–m lidar digital elevation model (DEM) provides sufficient resolution to examine the impact of variable till cover on the incision history of multiple small (5 km2) catchments in eastern Canada.  The study site was selected because it has homogeneous bedrock geology that dips parallel to the land surface, is tectonically stable, has undergone common base level changes, and has a common ice history, with variable overburden thickness, from thin cover in the west to thick cover in the east. Basin morphometrics were compared for similar-size basins that have variable till cover thicknesses. Basins with thicker till cover are wider and show differences in hypsometries compared to those where till cover is thin. Two basins representing end members of till thickness were measured for stream discharge and water chemistry. Thick till  (> 1 m) on the eastern half of North Mountain retards infiltration sufficiently to promote overland flow and accelerate incision relative to areas with thinner till.  Till thickness and continuity therefore are expected to impede the achievement of steadiness and may also delay stream power law relationships in larger catchments until till cover has been effectively eroded.SOMMAIREUn modèle altimétrique numérique (MAN) par lidar 4 m offre une résolution suffisante pour étudier l'impact des divers dépôts de till sur l'histoire de l'érosion linéaire de multiples petits (5 km2) bassins versants dans l'Est du Canada.  Le site d'étude a été choisi parce que sa géologie est homogène et que son pendage est parallèle à la surface du sol, qu’il est tectoniquement stable, qu’il a subi des changements similaires du niveau de base d’érosion, de même qu’ une histoire glaciaire similaire, avec une épaisseur de mort-terrain variable, d’une couverture mince à l'ouest jusqu'à une couverture épaisse à l'est. La morphométrie du bassin a été comparée à celle de bassins de taille semblable aux épaisseurs de till variables.  Les bassins aux couvertures de till plus épaisses sont plus larges et montrent des différences hypsométriques comparé  à ceux aux couvertures minces.  Deux bassins représentant les termes extrêmes de l'épaisseur du till ont été mesurées quant au débit du courant et à la chimie de l'eau.  Les till épais (>1 m) sur la moitié est du mont Nord retardent l'infiltration, ce qui favorise l'écoulement en surface et accélèrent l’érosion linéaire par rapport aux zones couvertes de couches de till plus minces.  On s’attend donc à ce que l'épaisseur de la couche de till et sa continuité agissent comme une entrave à la stabilité et puissent aussi retarder les effets de la loi de puissance de l’écoulement dans les grands bassins récepteurs jusqu'à ce que la couverture de till a été effectivement érodée.

scholarly journals Estimation of flash flood hazard in the Pidima-Arfara area (Messinia, SW Greece), based on the study of instantaneous unitary hydrographs, longitudinal profilesand stream power

2007 ◽  
Vol 40 (4) ◽  
pp. 1621
Author(s):  
E. Sambaziotis ◽  
I. Fountoulis
Keyword(s):  
Flash Flood ◽  
Flood Hazard ◽  
Flash Floods ◽  
Topographic Map ◽  
Stream Power ◽  
Longitudinal Gradient ◽  
Hydrological Simulation ◽  
Small Catchment ◽  
Map Scale ◽  
Good Agreement

In this paper it is an effort to combine different methodologies in order to locate the sensitive sites in flash flood phenomena in a relatively small catchment located north of Kalamata (Messinia SW Péloponnèse, Greece). Based on digitised topographic map (scale 1/5.000) the longitudinal, gradient and stream power profiles of the watercourses were constructed and the results (possibly sensitive to flash floods sites) were compared to ones that came from applying hydrological simulation, hydrographs as well as Instantaneous Unitary Hydrographs. The comparison showed that the results were in good agreement.

scholarly journals Bedrock river erosion through dipping layered rocks: quantifying erodibility through kinematic wave speed

2021 ◽  
Vol 9 (4) ◽  
pp. 723-753
Author(s):  
Nate A. Mitchell ◽  
Brian J. Yanites
Keyword(s):  
Wave Speed ◽  
Rock Strength ◽  
Numerical Models ◽  
Rock Properties ◽  
Kinematic Wave ◽  
Stream Power ◽  
New Approach ◽  
Migration Rates ◽  
Base Level ◽  
Landscape Morphology

Abstract. Landscape morphology reflects drivers such as tectonics and climate but is also modulated by underlying rock properties. While geomorphologists may attempt to quantify the influence of rock strength through direct comparisons of landscape morphology and rock strength metrics, recent work has shown that the contact migration resulting from the presence of mixed lithologies may hinder such an approach. Indeed, this work counterintuitively suggests that channel slopes within weaker units can sometimes be higher than channel slopes within stronger units. Here, we expand upon previous work with 1-D stream power numerical models in which we have created a system for quantifying contact migration over time. Although previous studies have developed theories for bedrock rivers incising through layered stratigraphy, we can now scrutinize these theories with contact migration rates measured in our models. Our results show that previously developed theory is generally robust and that contact migration rates reflect the pattern of kinematic wave speed across the profile. Furthermore, we have developed and tested a new approach for estimating kinematic wave speeds. This approach utilizes channel steepness, a known base-level fall rate, and contact dips. Importantly, we demonstrate how this new approach can be combined with previous work to estimate erodibility values. We demonstrate this approach by accurately estimating the erodibility values used in our numerical models. After this demonstration, we use our approach to estimate erodibility values for a stream near Hanksville, UT. Because we show in our numerical models that one can estimate the erodibility of the unit with lower steepness, the erodibilities we estimate for this stream in Utah are likely representative of mudstone and/or siltstone. The methods we have developed can be applied to streams with temporally constant base-level fall, opening new avenues of research within the field of geomorphology.

scholarly journals Quantifying Normal Fault Evolution from River Profile Analysis in the Northern Basin and Range Province, Southwest Montana, USA

Lithosphere ◽  
2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Ian P. Armstrong ◽  
Brian J. Yanites ◽  
Nate Mitchell ◽  
Clarke DeLisle ◽  
Bruce J. Douglas
Keyword(s):  
Normal Fault ◽  
Basin And Range ◽  
Fault Slip ◽  
Stream Power ◽  
Spatial And Temporal Patterns ◽  
Basin And Range Province ◽  
Slip Rates ◽  
Base Level ◽  
River Profiles ◽  
Fault Evolution

Abstract Over the past few decades, tectonic geomorphology has been widely implemented to constrain spatial and temporal patterns of fault slip, especially where existing geologic or geodetic data are poor. We apply this practice along the eastern margin of Bull Mountain, Southwest Montana, where 15 transient channels are eroding into the flat, upstream relict landscape in response to an ongoing period of increased base level fall along the Western North Boulder fault. We aim to improve constraints on the spatial and temporal slip rates across the Western North Boulder fault zone by applying channel morphometrics, cosmogenic erosion rates, bedrock characteristics, and calibrated reproductions of the modern river profiles using a 1-dimensional stream power incision model that undergoes a change in the rate of base level fall. We perform over 104 base level fall simulations to explore a wide range of fault slip dynamics and stream power parameters. Our best fit simulations suggest that the Western North Boulder fault started as individual fault segments along the middle to southern regions of Bull Mountain that nucleated around 6.2 to 2.5 Ma, respectively. This was followed by the nucleation of fault segments in the northern region around 1.5 to 0.4 Ma. We recreate the evolution of the Western North Boulder fault to show that through time, these individual segments propagate at the fault tips and link together to span over 40 km, with a maximum slip of 462 m in the central portion of the fault. Fault slip rates range from 0.02 to 0.45 mm/yr along strike and are consistent with estimates for other active faults in the region. We find that the timing of fault initiation coincides well with the migration of the Yellowstone hotspot across the nearby Idaho-Montana border and thus attribute the initiation of extension to the crustal bulge from the migrating hotspot. Overall, we provide the first quantitative constraints on fault initiation and evolution of the Western North Boulder fault, perhaps the farthest north basin in the Northern Basin and Range province that such constraints exist. We show that river profiles are powerful tools for documenting the spatial and temporal patterns of normal fault evolution, especially where other geologic/geodetic methods are limited, proving to be a vital tool for accurate tectonic hazard assessments.

scholarly journals Anatomy, Age and Origin of an Intramontane Top Basin Surface (Sorbas Basin, Betic Cordillera, SE Spain)

2018 ◽  
Author(s):  
Martin Stokes ◽  
Anne E. Mather ◽  
Ángel Rodés ◽  
Samantha H. Kearsey ◽  
Shaun Lewin
Keyword(s):  
Growth Patterns ◽  
Alluvial Fan ◽  
Betic Cordillera ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Surface Erosion ◽  
Se Spain ◽  
Surface Formation ◽  
Base Level ◽  
Basin Surface

Collisional mountain belts commonly develop intramontane basins from mechanical and isostatic subsidence during orogenic development. These frequently display a relict top surface, evidencing a change interval from basin infilling to erosion often via capture or overspill. Such surfaces provide markers that inform on orogenic growth patterns via climate and base level interplay. Here, we describe the top surface from the Sorbas Basin, a key intramontane basin within the Betic Cordillera (SE Spain). The surface is fragmentary comprising high elevation hilltops and discontinuous ridges developed onto the variably deformed final basin infill outcrop (Gochar Formation). We reconstruct surface configuration using DEM interpolation and apply 10Be/26Al cosmonuclides to assess surface formation timing. The surface is a degraded Early Pleistocene erosional pediment developed via autogenic switching of alluvial fan streams under stable dryland climate and base level conditions. Base level lowering since the Middle Pleistocene focused headwards incision up interfan drainages, culminating in fan head capture and fan morphological preservation within the abandoned surface. Post abandonment erosion has lowered the basin surface by 31 m (average) and removed ~5.95 km3 of fill. Regional basin comparisons reveal a phase of Early Pleistocene surface formation, marking landscape stability following the most recent Pliocene-Early Pleistocene mountain building. Post-surface erosion rate quantification is low and in accordance with 10Be denudation rates typical of the low uplift Betic Cordillera.

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