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Stream profile analysis and stream gradient index

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... The graded long profile is the long profile that the river would develop under dynamic equilibrium conditions, given the positions of its headwater and outlet. From among the multiple mathematical methodologies, we selected the stream-gradient index (SL) principle (Hack, 1973), which in principle seems to be the most suitable for bedrock rivers and has been widely used (e.g., Pérez-Peña et al., 2009;Troiani et al., 2014;Subiela Blanco et al., 2019;Piacentini et al., 2020;Viveen et al., 2021). First, the value of the total SL is calculated, given the present headwater and outlet positions for the studied stream (Fig. 1). ...
... SL is the slope value of the straight line that joins the headwater and the outlet of the longitudinal profile plotted in a semilogarithmic graph (Fig. 1). The obtained SL value is then introduced into Hack's equation (Hack, 1973): ...
... The S-A plot has been created, and the corresponding Ksn index calculation (Wobus et al., 2006) has been carried out in order to establish a comparison with the g values, especially with regard to the interpretation of the g-value trends. Stream power-law scaling or Flint's law, sets a continuous negative slope alignment that adjusts to a potential distribution under steady state or dynamic equilibrium conditions (Morisawa, 1962;Hack, 1973;Flint, 1974;Howard et al., 1994;Harel et al., 2016;Hergarten, 2020): ...
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Fluvial systems carve the Earth's surface under the influence of climate and tectonics. This process tends towards dynamic equilibrium conditions, in which rivers respond by regularizing their longitudinal profiles to a graded form. However, external forcings frequently interrupt this trend displacing the system to a transient state from which the system will evolve again with a tendency towards a graded form. In bedrock incising rivers, the longitudinal profile shape provides information on transient states, and quantifying the regularization level makes it possible to establish inferences about a river's evolutionary trend and its relationship with the influencing external forcings. This work presents a procedure for quantifying the regularization level of streams from the analysis of the shape of the longitudinal profiles. This procedure involves quantifying of the departure of the current shape of the longitudinal profile from that representing the graded long profile under dynamic equilibrium conditions. This comparison is quantified by two indices: ‘stream regularization index_G’, calculated for the entire long profile, and ‘regularization index_g’, calculated discretely along the long profile. To illustrate the usefulness of the indices and how they respond in different fluvial contexts and evolutionary stages, the longitudinal profiles of 14 streams from the central area of the Iberian Peninsula were analyzed. The results are interpreted together with the area-slope graph and the Ksn index, which corroborated the usefulness of this technique as a morphometric tool for quantifying the river maturity and identify tectonic regime transitions.
... The forest submerged under the flood during the 1950 great Assam earthquake, as per the information provided by the area's residents. The great Assam earthquake of 1950 caused great destruction, a dam formed by landslides eventually burst and caused the great flood in the Subansiri river [17,34]. The historic flood of 1950 contributed so much sediment that it deposited up to 1 m of coarser sediment comprising pebbles and coarse sand over the earlier flood plain alluvium, as can be seen in Chauldhoa ghat, Assam [17]. ...
... The great Assam earthquake of 1950 caused great destruction, a dam formed by landslides eventually burst and caused the great flood in the Subansiri river [17,34]. The historic flood of 1950 contributed so much sediment that it deposited up to 1 m of coarser sediment comprising pebbles and coarse sand over the earlier flood plain alluvium, as can be seen in Chauldhoa ghat, Assam [17]. ...
... The Stream Length-Gradient index can be used to evaluate any divergence in river longitudinal profile stability caused by tectonic, climatic, or lithological factors. [17]. Hack (1973) defined the stream length gradient index as SL = (∆H / ∆L). ...
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In this paper we evaluate the morphotectonics of the area around the Subansiri river in northeastern India. Research focuses on understanding the impacts on areas experiencing active tectonic deformation. It also explains the variety of kinematics observed in the area from the Miocene to the present. The tectonics can explain some structures related to the extensional tectonics predominant in the region and the development of the minor and major morph structures driven by faults with different kinematics. We developed a morphotectonic evolutionary model for the area based on the morphotectonic analysis and geological mapping. Morphotectonic indices used to evaluate the tectonic activeness in this study are Mountain Front sinuosity Index, Valley Floor Width to Valley Height Ratio, Asymmetry Factor, Transverse Topographic Symmetry Factor, Mountain Front Steepness Index, Basin Shape Index and Stream Length Gradient Index. There are numerous lineaments present in the study area which are trending in NW-SE and NE-SW direction.
... It is sensitive to the river slope. SL changing influences by tectonic activity, erosion resistance, climate and topographic features (Hack, 1973). In other words, a river gradient change produced by tectonic movement increases the value of SL. ...
... where ΔH is the change of elevation (m), ΔL is the length of reach (m) and L is the horizontal length (m) from the midpoint of the reach to river head. Figure 3. Mechanism of calculation of SL following steam (Hack, 1973). ...
... All types classification of each geomorphic index that indicated tectonic activities is shown in Table 1. Hack (1973) Moreover, there are white and pink sandstones, conglomerates and pebble sandstones, gray siltstones and claystone in the Cretaceous to Jurassic (JKpw). The Jurassic (Jpk) consists of reddish-brown siltstones and claystone. ...
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Phetchabun province, central Thailand is vulnerable to various geohazards, with the potential for significant harm to people and property. Phetchabun province has many lineaments that is a source of tectonic activities. In this study, terrain analysis techniques are used in order to determine geomorphic indices related to tectonic activity. we evaluate active tectonics using 30 meters resolution Digital Elevation Model (DEM) data, and a total of 38 drainage basins were extracted using ArcGIS software. we derived drainage network and geomorphic indices: stream-length gradient (SL), mountain front sinuosity (Smf), hypsometric integral (HI), hypsometric curve (HC), basin shape index (Bs). According to the result, the SL index is calculated in percentage on stream which selected 90 to 100 percentage to represent anomalous values. The Smf index computed for 207 lineaments. Most of lineaments has been supported the low active tectonics of the area. The HI values changes between 0.06 to 1.00. High value of HI indicates less impact from tectonic activity which has been found in the western and southern of the study area, The HC has 3 classes; results show most drainage basins in concave curves. The high value of Bs found in most drainage basins that are related to high tectonic activity. Additionally, the geomorphic indices are significantly affected by lithology especially sedimentary rocks that most found in the study area and structure geology.
... The satellite and elevation data acquired in the preliminary stage is used to analyze the morphotectonic evidences of the study area ( Fig. 1.6). Basin Shape (Bs) in the present work has been thoroughly evaluated, which can be used as basic reconnaissance tools to map areas undergoing rapid tectonic deformation and reveals about the level of tectonic activity undergoing in the area (Hare and Gardner, 1985;Ramírez-Herrera, 1998;Keller and Pinter, 2002;Hack, 1973;Strahler, 1952;Whipple et al., 2013;Kothyari et al., 2016b;Jani et al., 2021). These indices were merged into a single index called Relative Index of active tectonics (RIAT) to assign classes of relative tectonic activity (El-Hamdouni et al., 2008;Dehbozorgi et al., 2010). ...
... To map such fluvial terraces, river incision, and paleo-channels, LANDSAT satellite pictures were employed, as well as other image enhancement techniques in the GIS platform, and multiple paleo-channels in the mainland region were discovered, with the key paleochannels highlighted in Fig. 3.5. (Strahler, 1952;Hack, 1973;Bull and McFadden, 1977;Cox, 1994;). The novel technique GLA analysis has been the key factor which is used to demonstrate detecting landform changes produced by tectonic deformations along river courses Žibret, 2014, 2017;Talukdar et al., 2019;Kothyari et al., 2019b;Kandregula et al., 2020). ...
... Based on HI values, Strahler (1952) classiBed the cycle of erosion, i.e., the time needed for reducing a land tract to the base level (i.e., cycle of erosion), into three stages, viz., young (HI C 0.60), mature or equilibrium (0.30 B HI B 0.60) and monadnock stage (i.e., HI B 0.30). But Hack (1973) explained the concavity or curvature of river proBles as a primary signature of river erosion and, thus landscape evolution processes. Further, neotectonic control on 19 RBs has been investigated with the aid of SRTM-DEM data and detailed Beld evidences. ...
Article
Evolutionary geomorphologic stages of tropical river basins of southern Kerala, southwest India were investigated through the state-of-the-art hypsometry analysis and its attributes of 19 river basins (19 RBs). The empirical methodology act as an important tool to understand the relative relief asymmetries with respect to area and enlightens neotectonic controls. Present study on 19 RBs implies that underlying structures control the hypsometric curve (HC). Regression analysis of the basin areas (BA) and hypsometric integrals (HI) showed a positive correlation (R2 = 0.536) for BAs of 500 km2 (n = 4, P = 0.01), the relation becomes weak or negative. Inflection (I) points on the hypsometric curve (HC) of RBs showed least variation implying a slight disparity between the aspect of landform and its evolutionary state. For apprehending the RB evolution, the RBs have been classified into three zones based on major tectonic features. The expedient outcome of this study is the potential and rewarding application in the design and implementation of measures for conserving soil and water in RBs considered. This hypsometric analysis along with neotectonic evidence is together endowed best tool to understand the river basin behaviour and their response to various calamities. Further, it will give an insight to policy makers for future changes on land use.
... ΔH is the altitudinal difference between the uppermost and lowermost ends of the stream segment, ΔL is that segment's length, and L is total length of the stream upstream of that segment's midpoint (Hack, 1973). The index is effectively used in assessing spatial variability in the magnitude of tectonic activities in any region (Keller & Pinter, 2002). ...
Article
The NE–SW trending and SE dipping Thoubal‐Chandel Thrust (TCT) in eastern Manipur Hills of the Indo‐Myanmar Range (IMR) places the Thoubal‐Chandel thrust sheet over the Churachandpur‐Mao thrust sheet. Despite being seismically active, the active tectonic aspects of the major structural discontinuities within the IMR, including TCT, are not yet studied in detail. The present study aims to examine the active tectonics of the TCT and other associated faults, with particular focus on deformation of the Churachandpur‐Mao, and Thoubal‐Chandel thrust sheets. Association and disposition of landforms, and statistical analyses of Mountain‐front Sinuosity Index (Smf), Stream Length‐Gradient Index (SL), Hypsometric Integral (HI), Drainage Basin Asymmetry Factor, and Transverse Topography Symmetry Factor (T) reveal that both of these adjacently lying thrust sheets are actively uplifting due to oblique‐slip movement on their basal thrusts, but with spatially variable rates. In general, higher SL (mode = 219) and HI (mode = 0.527) in large parts suggest faster uplift of the Thoubal‐Chandel thrust sheet than the Churachandpur‐Moa thrust sheet, which has comparatively lower SL (Mode = 140) and HI (mode = 0.416). However, differential along‐strike uplift rates have caused tilting of both the thrust sheets. Faster uplift of the northern part of Thoubal‐Chandel thrust sheet has caused its overall southward down‐tilting, whereas faster uplift of the southern part of Churachandpur‐Mao thrust sheet has caused its overall northward down‐tilting. The study brings out that the deformation pattern of even the adjacent thrust sheets of growing orogens could be at stark variance albeit the same stress regime. The Thoubal‐Chandel Thrust (TCT) in eastern Manipur Hills places the Thoubal‐Chandel thrust sheet over the Churachandpur‐Mao thrust sheet. Geomorphic investigations reveal active uplift of these thrust sheets, but the uplift rates vary along the strike causing these adjacent lying thrust sheets' tilting in opposite directions.
... ΔH is the altitudinal difference between the uppermost and lowermost ends of the stream segment, ΔL is that segment's length, and L is total length of the stream upstream of that segment's midpoint (Hack, 1973). The index is effectively used in assessing spatial variability in the magnitude of tectonic activities in any region (Keller & Pinter, 2002). ...
Article
The NE–SW trending and SE dipping Thoubal-Chandel Thrust (TCT) in eastern Mani�pur Hills of the Indo-Myanmar Range (IMR) places the Thoubal-Chandel thrust sheet over the Churachandpur-Mao thrust sheet. Despite being seismically active, the active tectonic aspects of the major structural discontinuities within the IMR, includ�ing TCT, are not yet studied in detail. The present study aims to examine the active tectonics of the TCT and other associated faults, with particular focus on deforma�tion of the Churachandpur-Mao, and Thoubal-Chandel thrust sheets. Association and disposition of landforms, and statistical analyses of Mountain-front Sinuosity Index (Smf), Stream Length-Gradient Index (SL), Hypsometric Integral (HI), Drainage Basin Asymmetry Factor, and Transverse Topography Symmetry Factor (T) reveal that both of these adjacently lying thrust sheets are actively uplifting due to oblique-slip move�ment on their basal thrusts, but with spatially variable rates. In general, higher SL (mode = 219) and HI (mode = 0.527) in large parts suggest faster uplift of the Thou�bal-Chandel thrust sheet than the Churachandpur-Moa thrust sheet, which has com�paratively lower SL (Mode = 140) and HI (mode = 0.416). However, differential along-strike uplift rates have caused tilting of both the thrust sheets. Faster uplift of the northern part of Thoubal-Chandel thrust sheet has caused its overall southward down-tilting, whereas faster uplift of the southern part of Churachandpur-Mao thrust sheet has caused its overall northward down-tilting. The study brings out that the deformation pattern of even the adjacent thrust sheets of growing orogens could be at stark variance albeit the same stress regime.
... In connection with the structural task, the seismological outline also uncovers a positive tectonic format that signifies that the Diana-Rohtikhola fan is stable and that the Jiti-Khuji Diana is unstable. In an illustration of the study, geomorphic indices encompass the topographic evolution (Hack 1973), which is reflected through the stream gradient index (SL). The vertical incision has facilitated the steep gradient of Jiti, and the hypsometric integral indicates the degree of basin dissection with relative landform age (Ayaz et al. 2018). ...
Article
Abstract: Across the Himalayan foreland area, alluvial fans respond to fluvial depositional landforms created by active tectonics and are incorporated within hydro-sediment processes. Each tributary of the master stream has its water and sediment to discharge, which assists in initiating several mesolevel fans in response to the active tectonics in Jaldhaka basin. Along the mountain front, active MBT (Main Boundary Thrust), MFT (Main Frontal Thrust) and lineaments (parallel and transverse to Himalaya) have governed the tectonically active Quaternary foreland area where numerous meso-level fans have developed. The study aims to estimate the tectonic activeness of each meso-fan using the morphotectonic indicators. The tributaries of the Jaldhaka River are permuted to the recent tectonism or neotectonics to form each meso fan with its basin displaying the varying degree of their activeness and aggradation system. Statistical methods like technique for order performance by similarity to ideal solution (TOPSIS) and VIKOR (Vlse Kriterijumska Optimizacija Kompromisno Resenje) that specify multicriteria optimization and compromise solution, in Serbian have ranked the Fan 2 as mostly active and Fan 4 is comparatively tectonically stable. The hydro-sediment characteristics reveal the topographic spatial dynamics of Fan 4 where lobe 3 has elevated from 1984-2014. The XRD analysis specifies the scientific key in response to the dominance of dolomite in the aggraded elevated bed sediments carried by the Rohtikhola River. The conceptual fan models of Fan 2 and 4 display the fan development phases through four stages. It has clearly defined the extension of the fan lobes of Fan 2 and 4. It is summarized that within a common climatic zone and similar neo-tectonic setting, meso-level fans have differential morphotectonic signatures with dynamic aggradation processes. Keywords: Himalaya; Tectonic activeness; Fan dynamics; Hydro sediment interaction.
... When bedrock channels reach steady state, the longitudinal fluvial profile of the steady channel shows a smooth concave shape (Hack, 1973;Whipple, 2004). However, differences in the lithology, climate, and tectonic activity may alter the original balance between river erosion and the regional tectonic uplift rate, leading to discontinuities in the river, that is, knickpoints (Whipple and Tucker, 1999;Berlin and Anderson, 2007). ...
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The Helan Shan is located on the front edge of the expanding Tibetan Plateau. However, how the topography here responds to this propagation and its precise time constraints remain unknown. Based on the response process of fluvial landforms and tectonic evolution, we conducted a quantitative landform analysis of the Helan Shan region. Here, the spatial distribution features of various geomorphic indices were coupled, demonstrating that the mountain is tilting toward the west and north. The steeper downstream and gentle upper reaches indicate that the fluvial landforms have experienced an accelerated incision event, which can be attributed to the tectonic activity along the East Helan Shan Fault. Furthermore, the response time of the tectonic knickpoints ranges from 0.1 to 1.4 Ma based on the paleochannel reconstruction method. Combined with previous studies on low temperature thermochronology and active tectonics, we proposed a tectonic transformation model where the Helan Shan shifted the tilting model from the southwest to the northwest, as induced by the northeast expansion of the Tibetan Plateau from 0.1 to 1.4 Ma.
... The morphometric parameters like irregularity in mountain front, tilting of watershed, narrowness of valley with differential elevation of valley side, drainage orientation, gradient and maturity of the watershed provide analytical tools to assay the tectonic controls on the evolution of a drainage basin by modelling and statistical treatment of data (Horton 1945;Strahler 1952;Hack 1973;Bull and McFadden 1977;Keller 1986;Snow and Slingerland 1990;Bull 1991;Rhea 1993;Centamore et al. 1996;Demoulin 1998;Cox et al. 2001;Larue 2008;Guarnieri and Pirrotta 2008;P erez-Peña et al. 2009b;Raj 2012;Sharma et al. 2018). The indices that we analyzed include mountain front sinuosity index (Smf), asymmetry factor (AF), ratio of valley Coor width to valley height (Vf), hypsometric curve and hypsometric integral (HI), sinuosity factor (Sp). ...
Article
The Kachchh province of India has witnessed several major earthquakes in the past 100 years. These earthquakes have reactivated major faults of the region and modified the landscape. Morphometric analysis of the Wagad Highland was carried out to assess the vulnerability of regional fracture patterns for neotectonic activities. The analysis of regional fractures (using hypsometric curves and rose diagrams) of the first order drainage brought out the presence of three major orientations, i.e., N005°, N025° and N075°. Five quantitative parameters, viz., mountain front sinuosity (Smf), asymmetry factor (AF), hypsometric integral (HI), the ratio of valley floor width to valley height (Vf), and sinuosity parameter (Sp) were combined to a common parameter, the index for relative active tectonics (IRAT), having four classes (very high, high, moderate and low). The intensity of the neotectonic activity decreases from Class 1 to Class 4. About 62% (~151 km2) of the total area (~244 km2) is under Class 1 and Class 2, out of which ~50% (~122 km2) is in the western part of the study area. Based on these IRAT classes, a major NE–SW lineament, passing through the center of the study area, was identified to be neotectonically more active. Drainage basin morphometry of the Wagad Highlands (Rapar), India was analysed.Index for relative active tectonics (IRAT) supports very high neotectonic activity.IRAT map provides demarcation of neotectonically active zones.Seismicity in the Kachchh region is related to high strain along regional faults. Drainage basin morphometry of the Wagad Highlands (Rapar), India was analysed. Index for relative active tectonics (IRAT) supports very high neotectonic activity. IRAT map provides demarcation of neotectonically active zones. Seismicity in the Kachchh region is related to high strain along regional faults.
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The piedmont forming the southern foot-hill plain of the Himalayan mountain chain in the Jalpaiguri district of West Bengal, India, is composed of coalesced alluvial fan deposits of the Quaternary Period. Neotectonic dislocations affected the piedmont plain and controlled the river system that reincised the fan deposits. Stream length gradient index, sinuosity index, braiding index, channel migration, and change of position of the confluence of the Jaldhaka and Daina rivers are estimated for 90 years (1930–2020) to decipher the role of neotectonism and climate on the channel evolution pattern. Neotectonics have played a major role in the pattern of channel evolution. Still, variable monsoonal discharges have also controlled the channel characteristics to a large extent, particularly in the lower reaches.
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The diversity of structures and tectonic regimes in the Borborema Province caused the various morphostructural compartments to follow different evolutionary pathways throughout and after the fragmentation of Gondwana. In the northern Borborema Highlands, post-rift evolution occurred in a differentiated way, and the present study aims to understand how this occurred. For this, a set of morphological (geomorphological mapping, mapping of drainage anomalies, and extraction of relief lineaments) and morphometrics indexes (hypsometric curves, Basin Asymmetry Factor, Hack Index, Concavity Index, and χ Index) have been applied to drainage watersheds and low-order channels. The results obtained allowed us to propose a post-rift evolutionary model. To the north, the Highlands presents a recent divide resulting from a series of Cenozoic tectonomagmatic reactivations that promoted river rearrangement processes, such as drainage direction reversal and relief inversion—the current conditions of semiaridity and the absence of epigeny cause this drainage divide to remain stationary. The results diverge from the idea that only high relief margins were subject to greater tectonic control. Despite its modest altitudes, the transforming equatorial margin of Northeastern Brazil exhibits a significant recurrence of morphotectonic reactivation events, operating at different space-time scales. The area is also one of the sectors of the Brazilian passive margin with the highest record of modern seismicity.
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The work seeks to illustrate the applicability of morphometry in the investigation of processes of drainage rearrangement and relief configuration in the Iron Quadrangle, one of the compartments of the Brazilian Atlantic Plateau. To this end, the studies were concentrated in the Conceição River basin, a tributary of the Upper Doce River, southeastern Brazil. Indices that point out drainage migration processes and that allow inferences about the lithostructural and morphotectonic control of the hydrographic network were applied, namely: RDE (Declivity-Extension Ratio), FABD (Drainage Basin Asymmetry Factor), and FSTT (Transverse Topographic Symmetry Factor). In a complementary way, aspects of the morphology and geometry of the drainage were surveyed using satellite imagery. The results show evidence of model evolution from first-order knickpoints and channel migration as a result of structural rearrangements. An old tributary of a neighboring watershed (Barão de Cocais River) would have been pirated by a direct tributary of the Conceição River, indicating greater denudational aggressiveness of this basin.KeywordsFluvial geomorphologyDrainage network reorganizationStream piracyFluvial morphometry
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A drainage system responds swiftly on a regional or local scale to reveal the signature of neotectonic activities or any changes in climate. A few works in southern India have shown tectonic movements in terms of river and drainage response. The Gingee and the Vellar river basins (adjacent to the lower Kaveri Basin in Tamil Nadu) have been chosen for the present study. The morphometric analysis of the Gingee and the Vellar river basins and OSL dating of the sediments collected from the rivers' palaeochannels were carried out to achieve the proposed objectives. The study helped understand the role of climatic and tectonic elements in the evolution of the basins. The analysis indicates a regional scale-down warping shown by the southward tilting of the Gingee drainage systems and northward tilting of the Vellar drainage systems, strong asymmetry in some reaches (VRSB-II; III) and pronounced elongation of certain tributaries (GRSB-III; IV and VRSB-V). The Gingee River migrated clockwise (towards south) to its current position since the mid-Holocene period ∼3.5 ka, whereas the Vellar River shifted in an anti-clockwise (towards north) direction since 1.28 ka. This was the time when the study area experienced high precipitations. Also, these rivers are very coarse-grained bed load rivers found very shallow and thus, during heavy precipitation and discharges, prone to fill the channel quickly and shift the course. Luminescence ages of the paleochannels also suggest that both the rivers are migrating towards the central part with the same rate of ∼4.5km/ka.
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The continental margin of Northeast Brazil (NE Brazil) is the most seismogenic of the passive margin of South America and has several evidence of neotectonics. However, the duration and magnitude of neotectonic events cannot be uniformly replicated for a scale of ∼3000 km of extension. Therefore, this study aimed to understand the tectonic dynamics, especially from Neogene to recent, for a region little studied in this scope. We conducted multiscale analysis: landforms, sub-basins, drainage systems, and sedimentary outcrops. Applying a multi-technical approach: geomorphic indices (Stream Length-Gradient-Sl, Channel Steepness ksn, Basin Asymmetry Factor); use of Machine Learning Algorithms (ML) for spatialization of Sl and ksn indices; and OSL-palynology chronology. The results indicate multiphase tectonic control occurring by reactivation of geological faults from the Cretaceous to the recent, affecting shear zones, Cretaceous Basins, and Miocene deposits (Barreiras Formation). In these areas, predictions by ML (Sl and ksn indices) showed high values associated with fault zones, which confine and direct drainage, and landforms conditioning ungraded river long-profiles and tilted sub-basins. Tectonic deformations also manifest at the outcrop scale, with strata showing deformations (folds, joints, and atypical dips). Furthermore, strata with marine palynomorphs (Miocene) and Pleistocene-Holocene sediments (Post-Barreiras) in an altitudinal position above ∼38 m above sea level suggest post-depositional movement. The multiscale and multi-technical approaches showed that tectonic activity acted in different periods. Notably, the spatial prediction of geomorphic indices with ML is potentially competent in regional analyzes of neotectonics.
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Assam region is mainly formed by the deposit and erosion process of the Brahmaputra River. The frequency of seismic events results in landform deformation, which highly influences the drainage basin pattern and causes drainage anomalies, having a subsequent effect on the flood distribution pattern. In the present study, morphometric parameters and geomorphic indices for the Assam region are derived from SRTM DEM data of 30 m resolution using GIS to characterize the tectonic activity, which in turn influences the drainage pattern. The indices are classified into three tectonic activity classes, and the average of the classes is combined to generate the indices of relative active tectonics (IRAT). The four classes of IRAT are defined for the study area as (i) very high; Class 1 (1.57 – 1.80), (ii) high; Class 2 (1.81 – 2.06), (iii) moderate; Class 3 (2.07 – 2.26), and (iv) low; Class 4 (2.27 – 2.30). Class 1 corresponds to basins 1 and 6. Basins 2, 4, and 5 fall under Class 2. Class 3 consists of basins 7, 8, and 9, and Class 4 comprises basins 3 and 10. Results show that most of the study area lies in very high to moderate active tectonic zones and the identified zones are consistent with significant faults and thrusts present in the basins. The combined approach of GIS-based morphometric and geomorphic study allows for identifying deformed landforms resulting from active tectonics. The results can also be employed for the development of watershed management and sustainable land use planning.
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The morphological boundary between the Himalayas and the foreland plain is well expressed and most often corresponds to the frontal emergence of the Main Himalayan Thrust (MHT). This boundary is affected by surface ruptures during very large Himalayan earthquakes (Mw > 8) that regularly induce (with a recurrence of the order of 500 to 1200 years) the uplift of the foothills relative to the plain. However, a thrust-fold system is hidden beneath the plain and is displayed by the seismic profiles of oil companies in east/central Nepal and by H/V passive geophysical techniques in Darjeeling. Its long-term kinematic evolution is slow, with a tectonic uplift of the hanging wall that is lower than the subsidence rate of the foreland basin, that is, less than approximately half a millimetre per year. During phases of low sedimentation controlled by climatic fluctuations, the morphological surfaces of the piedmont are incised by large rivers for several tens of metres; therefore, structures hidden under the sediments emerge slightly in the plain. The evolution of the hidden structures corresponds to an embryonic thrust belt mainly affected by a long-term shortening rate of 1.4 +2.5/−1.2 mm·yr⁻¹, that is, 2–20% of the shortening rate of the entire Himalayan thrust system. Nonetheless, the details of the deformation associated with the embryonic thrust belt are still poorly understood. Several deformation components could affect the central Himalayan and Darjeeling piedmonts. i) Any slow steady-state deformation, such as layer parallel shortening (LPS) is not detected by Global Navigation Satellite System (GNSS) data, and such deformation would therefore absorb less than 0.5 mm·yr⁻¹. The geodetic data that suggest the aseismic growth of some of the structures are highly controversial. ii) For the rest of the deformation of the embryonic thrust wedge, it is yet to be proven whether deformation occurs during rare great earthquakes affecting the piedmont during medium earthquakes and/or during post-seismic deformation related to great earthquakes. The amplitude of this long-term low deformation is too limited to significantly reduce the seismic hazard in the seismic gaps of the Himalayan belt. iii) In some portions of the Himalayan front, such as Darjeeling (India), the thrust deformation related to great earthquakes propagates several tens of kilometres south of the morphological front in the zone previously affected by the long-term low deformation. It induces multi-metre surface ruptures in the piedmont and a mean shortening of 8.5 ± 6.2 mm·yr⁻¹. iiii) Pre-existing faults in the bedrock of the Indian craton, often oblique to the Himalayan structures, are locally reactivated beneath the foreland plain with low deformation rates.
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Rambiara River basin, a sub-basin of the Upper Indus, is dotted with fluvial and glacial geomorphic landforms. The presence of large number of glacial landforms like moraines, cirques, aretes, U-shaped valleys, etc. reflects the enormous erosive power of the past glaciers. During the Last Glacial Maximum (LGM), glaciers on average were 200 m thick and extended more than 10 km from the present-day cirque marks. Rock glaciers outnumber the clean glaciers that cover an area of 0.22 and 1.25 km2, respectively, in the basin. Glacial lakes are the prominent features in the higher reaches of the basin and occupy an area ranging from 0.01 to 0.70 km2. Downstream, the river is characterized by large channel width, anomalous sinuosity, braided pattern, and the presence of unpaired fluvial terraces. The large channel width depicts the enormous discharge from the glacial- and snow-melt during the Late Pleistocene when glaciers covered most of the Pir Panjal. After LGM, the glacier cover and the river discharge significantly decreased as highlighted by a large number of braided bars and the narrow stream to which the river is reduced. The warming trends observed across the Himalayas encompassing the Pir Panjal Range since the last century has further contributed significantly to the glacier recession in the basin.
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The Kumaun Himalaya registers frequent seismicity, neotectonic behaviour and incessant rainfall which accelerate hillslope processes governing landsliding phenomenon. Within the Kali Basin between Jauljibi and Garbyang, morphometric analysis of 45 fourth order sub-basins were carried out to prepare an erosion potential map of the region. The spatial distribution of 376 landslides including 158 debris slide and 97 rockfalls correlates well with the erosion map depicting 40% landslides in very high zone, 15% in high zone, 33% in moderate zone, 12% in low zone across the Kali Basin. The dominant parameters responsible for the erosion were evaluated using statistical methods such as Principal Component Analysis (PCA) and Agglomerative Hierarchal clustering (AHC). The comparison of PC1, PC2 and PC3 illustrates high erosion activity around the Main Central Thrust (MCT) and within the Vaikrita and Chipplakote formations which strongly reflect the function of basin dimension, bifurcation ratio, drainage density, relief and shape parameters for sub-basins exhibiting high proneness to flooding and typical surface runoff. The PCA results are consistent with AHC, where AHC clusters correspond with PCA factor loadings. Morphotectonic analysis using steepness index (Ksn) and valley floor width to height ratio (Vf) for the Kali and Dhauli rivers were integrated with landslide inventory that indicate the highest landslide density across the active Seraghat-Tintola Fault (STF) near Tawaghat and moderate to high density near topographic fronts of closely spaced active Lasku Fault (LF), Ghatibagar Kalika Fault (GKF) Rauntis Fault (RF) that outcrop within the Lesser Himalayan Sequences(LHS) exposed between Dharchula and Jauljibi. The study provides an understanding of quantitative geomorphometry as an useful approach to identify potentially active zones for slope failures and provide a guide to decision-makers in regional planning and mitigating the landslide hazard in the Kali valley which is developing hub for large scale infrastructural and tourist activities.
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We studied geomorphic indices related to tectonics along the Borpani River using Cartosat 10 m spatial resolution Digital Elevation Model (DEM) data. A total of 11 geomorphic indices such as transverse topographic symmetry factor (Tt), drainage basin asymmetry (AF), valley floor width to valley height ratio (Vf), bifurcation ratio (Rb), hypsometric integral (HI), basin elongation ratio (Re), basin shape index (Bs), circularity ratio (Rc), drainage density (Dd), relief ratio (Rh), hypsometric curves (HC) were studied to access the tectonics along the river in selected locations. Five locations along the river were selected for detailed analysis (sub-basin I, II a, II b, III, and IV). Horton's (1945) scheme was adopted for watershed delineation, while stream ordering was performed using Strahler's (1964) method. The results infer that the sub-basins along the Borpani River are tectonically active. In the case of sub-basin I, 3 geomorphic indices out of 11 falls in the category of highly active, and 2, 1, 2, and 4 indices out of 11 falls in the category of highly active in the case of sub-basins II a, II b, III, and IV. Similarly, 4, 1, 3, 6, 1 and 4, 8, 7, 3, 6 indices fall under moderately active and low active classes in sub-basins I, II a, II b, III, and IV. On average, 23.86 %, 29.54%, and 46.58% of the geomorphic indices fall in the active, moderately active, and low active classes.
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A bacia hidrográfica do rio da Chata tem como principal característica um controle estrutural de sua drenagem que se reflete nas unidades geomorfológicas e na morfologia do canal principal. A drenagem segue a direção dos trends regionais SW-SE/NW-SE, assim como, o rio da Chata sofre uma inflexura que muda abruptamente a direção do canal fluvial condicionado pela falha de empurrão e a Zona de Cisalhamento (ZC) dextral. Posteriormente, o canal principal da bacia se encaixa sobre uma ZC sinistral seguindo de forma retilínea até a sua foz sobre o vale estrutural. Ao longo do percurso o canal vai se adaptando as estruturas geológicas subjacentes onde, por vezes, é comandado pela erosão diferencial, ora pela ação direta das falhas e Zonas de Cisalhamento.
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As the secondary fault of the Niushoushan-Luoshan Fault Zone, the Liumugao Fault records the northeastward expansion of the Tibetan Plateau. Based on WorldDEM data, 11 rivers (R1-R11) that flow across the Liumugao Fault and their drainage basins were extracted using ArcGIS technology and a MATLAB script. The longitudinal profiles, Hack profiles, and stream length-gradient (SL) indexes of these rivers, as well as the hypsometric integral (HI) of their drainage basins, were extracted and calculated and combined with field observations to quantitatively analyze the activity of Liumugao Fault. The results show that: (1) the longitudinal profiles of the 11 rivers are steep, the Hack profiles of most rivers drop sharply at the main fault, and the average HI value of the drainage basins is ∼0.4. These phenomena indicate that the current activity of the fault is strong. (2) The average HI values of the drainage basins in the northern, middle, and southern segments of Liumugao Fault are 0.32, 0.37 and 0.45, respectively. Accordingly, the average normalized stream-gradient (SL/K) values of the three segments are 3.72, 4.64 and 7.16, respectively. These data show that the activity of the Liumugao Fault gradually increases from north to south.
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The geomorphology of the Deccan Volcanic Province (DVP) has its foundation in the eruption of flood basalts that covered nearly half of the Indian Peninsula during the Cretaceous – Paleogene transition and the asymmetric eastward tilt of the Peninsula. The northward trajectory of the Indian plate through the tropics leading to its collision with the Asian plate and the emergence of the Himalayan ranges are known to have resulted in significant climate changes through the Cenozoic. The DVP terrain preserves an imperfect, patchy record of these events and their impact on landscape evolution in an emergent continental block through the Cenozoic. The subhorizontal disposition of the stacks of lava flows in the DVP was interpreted to manifest the post-eruptive tectonic stability of this terrain. Earlier interpretations of the geomorphic characters of this terrain, with its step-like slope-profiles were consequently attributed to dominant climatic control. We review the regional topographic framework with additional inputs from the structural framework of the Deccan flood basalts, characters of the major rivers draining the province largely based on their high scale longitudinal profiles and Quaternary hinterland sedimentary basins within the DVP. It is evident that the erstwhile interpretation of the DVP as a singular morphotectonic unit where the antecedent drainage responded to Cenozoic tropical climate change with subsidiary tectonic controls requires re-examination. The DVP geomorphology is a collage of blocks bounded by ancient tectonic zones that were reactivated during Cenozoic events. Its landscape evolution is largely carved by an antecedent tropical drainage, that was modified by Paleogene and Neogene intracontinental block movements driven by far-field stresses derived from the ridge-push of the Indian Ocean in the south and slab-pull of the subducting Indian Plate in the north. The component blocks of the DVP have differing morphotectonic characters because of the subtle diversity in their relative uplift / sag trajectories and structural characters. The influence of the monsoon climate (with alternating wet and arid phases) on landscape evolution in the subprovinces of the DVP is likely to be less significant than was earlier believed. The Deccan landscape provides an example of how lithological and climatic controls on drainage evolution can be overprinted by weak midcontinental tectonics.
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Flood is the most common natural hazard that causing unprecedented loss of life and property in the world. In recent years, flood damage has increased due to human intervention and land use and climate changes. The purpose of this study is to predict flood susceptibility in Tafresh watershed in Markazi Province, Iran based on K-nearest neighbor (KNN), Extremely Gradient Boosting (XGB) machine learning models and evaluate the performance of hybrid genetic algorithm (GA) optimization method and XGB model. For this purpose, 14 independent variables affecting flood susceptibility were prepared, also, 227 flood locations were identified as independent variables based on available information and field survey. In order to evaluate the efficiency of the models, receiver operating characteristic (ROC) parameters were used. Evaluating the efficiency of the models based on the AUCs of testing dataset showed the higher efficiency of the GA-XGB hybrid model in modeling flood susceptibility in the Tafresh watershed is compared to KNN and XGB models, and the AUC in KNN, XGB, and GA-XGB models are 0.82, 0.85, and 0.87, respectively. So using the genetic algorithm as an optimizer for determining the best parameters in the XGB model increases efficiency in this model. The results of determining the relative importance of independent variables in flood susceptibility modeling showed that the independent variables considered in each model have different effects. Distance from road and distance from river in all three models had significant importance in modeling flood hazard in the Tafresh watershed. The optimization method in this study can be used as a powerful method in other spatial modeling studies. The results of this study also support management programs to reduce flood risks in the study area.
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The geomorphic changes over the earth’s crust are influenced by tectonic activities. These geomorphic changes are remnants of deformation that occurred in the recent geological past. Geomorphic features can be quantified to assess relative tectonic activity and response of landscape to active tectonics, regional structures, lithology and climate. To achieve the objectives, we evaluated the relative tectonic activity of the Garhwal synform, for which six major river basins were selected. The relative tectonic activity of all the basins is computed based on quantitative analysis of geomorphic indices. Quantitative analysis of each geomorphic parameter has been carried out, and a combined product of relative tectonic activity index (TAI) was derived for each basin. The TAI is classified into three classes based on their relative tectonic activity; basins having TAI value ≤1.75 (basins I, II and III) are placed in very high tectonic activity class, basin with a value ranging >1.75 to <2.0 are categorised as moderately active basins (basin ‘IV’), while basins having values >2.0 are less active (basins V and VI). A relative tectonic activity map of the area suffices for the prioritisation of each basin based upon their TAI. Furthermore, analysis of the longitudinal profile of rivers for knickpoint, precipitation and temperature variability over the last 100 years and seismic events since the last 100 years have been studied to interpret the tectonic regime and their influence on landscape evolution. The regional seismicity data suggest that the area falls in a seismic gap and has not experienced a great earthquake in recent history but have received seismic events of moderate intensity in the past. We opine that the Garhwal synform is tectonically active, and thus, significant steps should be taken for seismic risk assessment along with preventive measures. We also suggest that the influence of tectonic activities in the southeastern part of the Garhwal synform comprised by basins V and VI is relatively less than the rest of the basins. Finally, the six basins were prioritised based on their relative tectonic activity. Assessment of geomorphic indices from 30 m shuttle radar topography mission-digital elevation model (SRTM-DEM) in six drainage basins of the Garhwal Himalaya.Six river basins categorised under relative tectonic classes based on the calculation of geomorphic indices.Correlation of the large-scale geological setting and drainage basin dynamics contemplated with field evidence and regional seismicity.Quantification of relative tectonic activity index (TAI) of six river basins in the Lesser Himalaya of the Garhwal Himalaya. Assessment of geomorphic indices from 30 m shuttle radar topography mission-digital elevation model (SRTM-DEM) in six drainage basins of the Garhwal Himalaya. Six river basins categorised under relative tectonic classes based on the calculation of geomorphic indices. Correlation of the large-scale geological setting and drainage basin dynamics contemplated with field evidence and regional seismicity. Quantification of relative tectonic activity index (TAI) of six river basins in the Lesser Himalaya of the Garhwal Himalaya.
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Channel steepness index, ks, is a metric derived from the stream power model that, under certain conditions, scales with relative rock uplift rate. Channel steepness index is a property of rivers, which can be relatively easily extracted from digital elevation models (DEMs). As DEM data sets are widely available for Earth and are becoming more readily available for other planetary bodies, channel steepness index represents a powerful tool for interpreting tectonic processes. However, multiple approaches to calculate channel steepness index exist. From this several important questions arise; does choice of approach change the values of channel steepness index, can values be so different that choice of approach can influence the findings of a study, and are certain approaches better than others? With the aid of a synthetic river profile and a case study from the Sierra Nevada, California, we show that values of channel steepness index vary over orders of magnitude according to the methodology used in the calculation. We explore the limitations, advantages and disadvantages of the key approaches to calculating channel steepness index, and find that choosing an appropriate approach relies on the context of a study. Given these observations, it is important that authors acknowledge the methodology used to calculate channel steepness index, to ensure that results can be contextualised and reproduced.
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The Kongur Shan and Muztaghata massifs, bounded by the Kongur Shan extensional system (KES), represent tectonic and topographic anomalies in the eastern Pamir region. They are ideal examples to study how normal faulting and surface erosion influence Quaternary exhumation of the dome system. We apply multiple geomorphic parameters, including hypsometric integral, stream length-gradient index, drainage basin shape, drainage basin asymmetry and ratio of valley floor width to valley height, for the catchments on both sides of the range. We first evaluated the validity of various indices and chose three active tectonic-sensitive indices to establish a newly-integrated parameter ( Iat ) that is used to measure relative intensities of tectonic activity in active orogens. Results suggest stronger tectonic activity west of the domes along the Kongur Shan normal fault (KSF) and Muji dextral strike-slip fault, compared to the eastern side, along the Ghez and Kalagile faults. This first-order observation reflects tectonic control on the topographic development of the domal structure, consistent with eastward crustal tilting, attested by older thermochronology ages to the east. On the western flank of the range, stronger tectonic activity occurs mostly on the Muji fault, Kingata Tagh - Kongur Shan fault segment, as well as along the western and southern Muztaghata segments of the Kongur Shan fault. This is consistent with field investigations of Quaternary offsets of landforms, which suggest continuous activity of the Muji fault and KSF since the late Miocene. Average basin-wide erosion rates derived from stream power models are highest near the Kongur Shan dome, and gradually decrease southwards and northwards, in agreement with the spatial pattern of long-term exhumation rates in the footwall of the KSF obtained by low-temperature thermochronology data. Positive correlation between exhumation/erosion rates and extensional rates along the active faults located west of the domes indicates that extensional deformation likely plays a dominant role in controlling focused dome exhumation/erosion. However, considering peaked exhumation/erosion rates, stronger rock resistivity and steeper glacial landforms, attest to the important role of glacial buzz-saw in reshaping the recent dome’s landscape.
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Despite being a very common phenomenon worldwide, in Brazil, the factors and mechanisms that control gully erosion on a regional scale are still little known, which leads to the neglect of this environmental hazard by territorial and environmental management policies. In order to reducing this gap, we explored the potential of four common supervised machine learning algorithms, named random forest (RF), logistic regression (LR), naïve Bayes (NB) and artificial neural network (ANN) to produce gully erosion susceptibility models for two gullied watersheds, located in the state of Minas Gerais, southeastern Brazil. The modeling was based on the construction of a solid gully inventory and a database consisting of fifteen geo-environmental factors (GEF), whose influence was determined from the information gain ratio (IGR) and two bivariate statistical methods, named frequency ratio (FR) and modified information value (MIV). The predictive performance of the models was evaluated by the area under the receiver operating characteristic curve (AUC), overall accuracy (ACC) and sufficiency analysis. The results revealed that random forest achieved the highest overall performance in correct prediction of gullies and produced the most realistic gully susceptibility maps. The IGR data indicated that all GEF considered in the analysis contributed to the predictive model, although lithology, elevation and rainfall are the most influential variables. From an integrated analysis between the gully inventory, field observations, FR and MIV values, we found that gullies seem to be triggered by high annual average rainfall, but only develop where a set of specific geo-environmental conditions occur simultaneously. Finally, despite the limited land use data available, anthropogenic activities do not seem to affect the regional distribution pattern of gullies, although we have not excluded their local influence in triggering some erosive features.
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The present study area, Dadra and Nagar Haveli, contains several lineaments and traces of active faults. The various aspect of the geomorphic analysis, i.e., stream length (SL) gradient, hypsometric integral (HI), basin shape (BS), valley floor (VF), have been applied to evaluate the relative index of active tectonics (RIAT) of the Damanganga watershed. The high and low zones of tectonic activity have been identified based on the geomorphic analysis of the watershed. After evaluation of all indices, three classes, class II- high (1.3 ≤ RIAT < 1.5), class III- moderate (1.5 ≤ RIAT < 1.8), and class IV- low (1.8 ≤ RIAT), have been obtained to outline the degree/gradation of comparative tectonic activities in the study area. The appraised outcome of the RIAT dispersal is also well reinforced by the geomorphic evidence in the field. The collective outcomes of geomorphic evidence, such as stream deflection and analysis of lineament, deflection of streams, and geomorphic indices, conceal that the Damanganga watershed is affected by tectonic activity.
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The Fansipan and Tule mountain ranges, northern Vietnam, are regions with high elevations and are adjacent to the Red River Fault, which is an important structure that is related to the India-Eurasia collision. How mountain elevations are maintained today under a humid subtropical climate is important for improving the knowledge of the tectonic deformations in northern Vietnam and may have broader implications for the crustal dynamics of circum-Tibetan regions. We therefore utilized observations from field and digital elevation model (DEM) data and geomorphic analyses to constrain the active fault systems that have likely contributed to the uplift of mountain ranges. Our observations from DEM and field data indicate potential active normal and strike-slip faults such as the Phong Tho-Nam Pia Fault, Tule Fault, and Nghia Lo Fault. In addition to these observations, the results from geomorphic indices, which include both the stream-length gradient index (SL) and normalized steepness index (k sn ), present high values for the footwalls of the inferred normal faults and low values for the hanging walls. Most of the identified knickpoints are related to the locations of mapped faults. Correlations of these data indicate that recent movements of the Fansipan and Tule mountain ranges are dominated by strike-slip and normal faulting under a NE-SW minimum extensional regime. We therefore propose that extensional tectonics associated with isostatic rebound likely plays a role in maintaining mountain elevations over long periods despite the continuous weathering and erosion present in monsoon-affected areas.
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The exceptional concentration of vertebrate diversity in continental freshwaters has been termed the “freshwater fish paradox,” with > 15,000 fish species representing more than 20% of all vertebrate species compressed into tiny fractions of the Earth’s land surface area (<0.5%) or total aquatic habitat volume (<0.001%). This study asks if the fish species richness of the world’s river basins is explainable in terms of river captures using topographic metrics as proxies. The River Capture Hypothesis posits that drainage-network rearrangements have accelerated biotic diversification through their combined effects on dispersal, speciation, and extinction. Yet rates of river capture are poorly constrained at the basin scale worldwide. Here we assess correlations between fish species density (data for 14,953 obligate freshwater fish species) and basin-wide metrics of landscape evolution (data for 3,119 river basins), including: topography (elevation, average relief, slope, drainage area) and climate (average rainfall and air temperature). We assess the results in the context of both static landscapes (e.g., species-area and habitat heterogeneity relationships) and transient landscapes (e.g., river capture, tectonic activity, landscape disequilibrium). We also relax assumptions of functional neutrality of basins (tropical vs. extratropical, tectonically stable vs. active terrains). We found a disproportionate number of freshwater species in large, lowland river basins of tropical South America, Africa, and Southeast Asia, under predictable conditions of large geographic area, tropical climate, low topographic relief, and high habitat volume (i.e., high rainfall rates). However, our results show that these conditions are only necessary, but not fully sufficient, to explain the basins with the highest diversity. Basins with highest diversity are all located on tectonically stable regions, places where river capture is predicted to be most conducive to the formation of high fish species richness over evolutionary timescales. Our results are consistent with predictions of several landscape evolution models, including the River Capture Hypothesis, Mega Capture Hypothesis, and Intermediate Capture Rate Hypothesis, and support conclusions of numerical modeling studies indicating landscape transience as a mechanistic driver of net diversification in riverine and riparian organisms with widespread continental distributions.
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This study uses topographical factors to quantitatively describe the uplift amplitude of the plate movement, collects and analyzes the long-term series of rainfall, earthquakes, landslides and debris flows in watersheds from 1993 to 2019, explores the evolution mechanism of landslides, and uses conceptual models to map the areas prone to occurrence of potential debris flows in central Taiwan. Results show that the topographic factors of a watershed can effectively reflect the concavity index (θ) of the crustal uplift, and the spatial distribution of the concavity index in the watershed can be easily estimated. Combining the spatial distribution of concavity index and stream order, a watershed-scale potential debris flow map can be obtained. According to the interpretation rate change of the relationship between the concavity index and the watershed collapse rate, we can understand the occurrence time of landslides and/or debris flows, as well as the sediment transport dynamics of the watershed. The change of the interpretation rate of the concavity index to the collapse rate can be used as a guideline for the establishment of a debris flow warning system.
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The paper presents an attempt to recognize areas of enhanced erosional dissection, based on a combined analysis of several geomorphometric variables and using four different approaches (rank-based, cold and hot spot analysis, k-means clustering of 'raw' data, and k-means clustering of local measures of spatial autocorrelation). The study area includes the Orlickie-Bystrzyckie Mountains Block (OBMB), which is a block-faulted range within the Sudetes Mountains, Central Europe, typified by fault-generated range fronts, remnant planation surfaces and topographic ramps due to large-scale tilting. Geology is diverse, with basement rocks and sedimentary cover, and the relevant timescale is late Cenozoic. Morphometric variables derived from a LiDAR-based DEM include contour length, standard deviation of elevation, median valley depth and standard deviation of curvature, and are considered to account for various morphometric signatures of erosional dissection. While deriving compound measures of dissection, three grid cell sizes were considered. Within the OBMB several areas were identified as erosionally dissected to a considerable degree. Their spatial pattern is complex and reflects several factors simultaneously. Differential uplift appears as the main trigger, but the erosional response varies, depending mainly on the size of runoff contributing area-itself related to the pattern of uplift, and the distance from the margins of elevated areas. Lithology (bedrock resistance to erosion) seems to play a subordinate role. We also discuss various issues related to the procedures themselves, pointing out their advantages and limitations. Procedural setups proposed in this paper are not site-specific and may be used in various topographic and geological settings.
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The Gulf of Corinth is a rapidly opening area with high seismicity associated with extensive building collapses, destruction of cities, and even the deaths of inhabitants. Rapid residential development, especially in the southern part of the Gulf of Corinth, and the construction of crucial technical infrastructures necessitate understanding the activity across crustal-scale faults that host devastating earthquakes. The evolution of landforms affected by fault action is a dominant issue in geological science. In the present study, was selected the 20 km long Xilokastro pure normal fault. In this fault, we apply eight geomorphological indices in footwall catchments that drain perpendicular to its trace. In total, more than 5000 measurements were made in 102 catchments. The determination of geomorphological indices requires the construction of morphological profiles either perpendicular to the faults or perpendicular to the main tributaries of the drainage basins under consideration through the use of the geographical information systems (ArcGIS platform). Τhe application of these indices along catchments draining the Xilokastro fault scarp show high active tectonics. Its high activity is evidenced by the high values of the length-slope index near the fault trace, the low values of the width to height ratio index, the strong asymmetry of the drainage basins, especially in the overlapping zones between its segments, and the elongated shape of the drainage basins. This study supports the idea that the application of a single morphometric index is unable to reflect the distribution of active tectonics across faults, which makes inevitable the systematic comparison of a series of tectonic morphometric indices from which a new combined index emerges (Iat). The Iat classifies the Xilokastro fault in the high degree of activity at a rate of 75% of its length.
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Cirques are typical erosional landforms of glaciers and have been used as bases for paleoclimate and paleoenvironment reconstruction and for understanding the interactions between glacial erosion, climate, and topography. The availability of high-resolution digital elevation models (DEMs) provides the opportunity to map large populations of cirques for regional and global scale analysis. However, cirque outlines are still mainly determined based on manual digitization, which is time consuming and labor intensive. This paper introduces an automated method to recognize and delineate cirques using DEMs based on a series of hydrological and morphological analyses, including delineating stream network, filtering streams, determining potential cirque threshold points, and delineating cirque outlines. A semi-automated tool is also developed based on user-specified threshold points or cross sections. The related tools are coded in python and imported into ArcGIS as a toolbox, AutoCirque, with user friendly interfaces. Comparison in a test area of the eastern Tian Shan, China, indicated that the population statistics are relatively consistent between manually digitized and auto-delineated cirques. Detailed comparisons for 11 selected cirques indicated that the AutoCirque-delineated and manually digitized cirque outlines are similar in shape with an average boundary offset of approximately one DEM cell size (30 m) and a 70–90% overlap-fit percentage. The derived cirque metrics are also similar, especially for elevation, slope, and aspect related metrics. This toolbox can significantly speed up the analytical processes, remove the subjectivity in delineating cirque outlines, and allow for the comparison of cirque morphology and metrics at regional and global scales.
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The Abu-Dabbab area, located in the central part of the Egyptian Eastern Desert, is an active seismic region where micro-earthquakes (≈ML < 2.0) are recorded regularly. Earthquake epicenters are concentrated along an ENE–WSW trending pattern. In this study, we used morphological indexes, including the valley floor width-to-valley floor height ratio (Vf), mountain front sinuosity (Smf), the asymmetry factor index (Af), the drainage basin shape index (Bs), the stream length–gradient index (SL), hypsometric integral (Hi) water drainage systems, and a digital elevation model analysis, to identify the role of tectonics. These indexes were used to define the relative tectonic activity index (RTAI), which can be utilized to distinguish low (RTAI < 1.26), moderate (RTAI = 1.26–1.73), and high (RTAI > 1.73) tectonic activity signals all over the study area. Firstly, our results indicate low to medium tectonic activity and general anomaly patterns detected along the major tectonic zones of the study area. Secondly, based on most of the low to medium tectonic activity distributed in the study area and the detected anomalies, we discuss two potential drivers of the seismicity in the Abu-Dabbab area, which are fault-controlled and deep-rooted activities.
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The Fátima Basin is a small Cretaceous interior basin that was formed within the continental Borborema Province in northeastern Brazil. Its formation was related to the opening of the southern Atlantic Ocean. This study investigates the hypothesis of post-rift tectonic reactivation within this basin through an integrated set of geophysical (aeromagnetic), surface (outcrops), and subsurface (boreholes) data to model the tectono-stratigraphic framework of the basin. An analysis of several morphometric parameters, including the slope index, relief aspect, stream profiles, asymmetry factor (AF), stream-gradient index (SL), and valley floor width-to-height ratio (VF) was used to identify possible tectonic adjustments related to post-rift stress fields. The integration of geophysical and subsurface data showed that the basin possesses a half-graben geometry with the main basin axis trending NE-SW. Two families of topographic lineaments were identified: 1) NE-SW, corresponding to the main shear zones and faults of the Pre-Cambrian basement, and 2) NW-SE, representing faults and fractures in the adjacent basement and the sedimentary cover. A digital elevation model revealed that the maximum topographic elevation was 950 m, associated with deposits of the Paleozoic Tacaratu Formation located over the hinge line of the flexural margin of the basin. The AF values in the basin ranged between 25 to 76, and first- and second-order SL index anomalies were frequent, especially in the faulted border, the southeast sector, and the northeast sector. Analyses of the main river channels revealed VF values of around 1, which indicate active incisions in the river valleys. We suggest that the basin was subjected to differential uplift during the Cenozoic, which strongly affected the southeast and northeast sectors. Based on the exhumation of the Tacaratu Formation deposits, we estimate that the basin experienced approximately 500 m of uplift that influenced the erosion of Cretaceous deposits and adjacent basement rocks.
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Geomorphic indices (e.g., the normalized channel steepness index (Ksn) and the stream length-gradient index (SL)) highlight changes in fluvial shapes and gradients. However, the application of these indices was seldom used to identify potential landslide zones. In this study, we used the Ksn and SL indices to detect the significant variations in the stream power along river reaches, which are anomalies associated with landslides, in the Zengqu River watershed, the upper reaches of the Jinsha River. Most of the landslide anomalies originate along the trunk and surrounding tributaries below the knickpoint of the mainstream. This suggests an erosional wave is migrating upstream throughout the drainage area. The fluvial incision may generate over-steepened hillslopes, which could fail in the future. In addition, the divide asymmetry index (DAI) predicts the direction of the divide as the headwaters migrate toward lower relief, higher elevation surfaces. Landslides are expected to occur as the unstable divide migrates. The proposed methodology can benefit the detection and characterization of potential landslide zones. It should improve hazard and risk analysis and the identification of drainage network areas associated with landslides.
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The quantitative description of valley profiles is useful for understanding their geomorphological and dynamic features. To this end, the cross-sections of 45 valleys in the Kahar, Taft, and Granite formations in the Yazd–Ardakan catchment were investigated. Fractal properties, mathematical functions, the ratio of valley floor width to valley height (Vf), and the ratio of valley depth to valley top width (Fr) were used to study the morphology of the valleys. The average Vf values calculated for the Kahar, Taft, and granite formations were 5.56, 3.52, and 1.38, respectively. The average Fr values for these three formations were 0.07, 0.12, and 0.17, indicating the heterogeneity of lithological composition and structural status of the valleys. The multifractal analysis of valley cross-sections showed the transition of valley sections from a monofractal to multifractal nature. Therefore, the multifractal analysis seems appropriate for evaluating complexities in the valley and geomorphological properties of the catchment under study.
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Tectonic geomorphology is one of the youngest branches of geomorphology, helping to merge the vast fields of geomorphology and tectonics. Tectonic geomorphology has several main areas of emphasis, which include: landscape evolution of active plate margins; mountain building; development of active fault and fold systems; the evolution of passive margins, continental interiors and plateau uplift; geomorphology volcanoes and associated features; paleoseismology and seismic hazard assessment; the interaction of tectonics, climate, and surface processes, and polygenetic landscapes; and hazard mitigation. These areas of reflect the growth of new studies in tectonics, climate and Earth surfaces processes, and technological advances such as remote sensing, unmanned aerial vehicles, GPS, computers, geochronology, shallow geophysics, and geochemistry.
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Drainage basin-scale morphometric analysis and morphological evidence of tectonics represent helpful tools to evaluate and investigate morphoneotectonic processes in tectonically active regions. In this perspective, we applied an integrated analysis to the Abruzzo Periadriatic Area, between the Tronto and Sinello rivers (Central Italy). It involved morphometric analysis, structural geomorphological field mapping, and detailed analysis of fluvial terraces. Geomorphic indexes and markers (e.g., Irta, SL index, ksn, and knickpoints) were used in this study to detect the response of landscapes to drainage systems’ unsteadiness and tectonic deformation processes, possibly induced by the ongoing activity of the buried tectonic structures. Furthermore, the investigation of morphological field evidence of tectonics, integrated with the analysis of fluvial terraces’ spatial and temporal arrangement, was performed to assign relative, geomorphologically-based, age constraints of the landscape evolution. The resulting data allowed us to define domains affected by different morphostructural and morphoneotectonic processes, related to the impact and ongoing activity of the five detected families of structural elements (S1, F1, F2, F3, and F4), mainly characterized by compressive, extensional, and transtensive kinematics. Finally, this study could represent a scientific basis for integrating morphometric, fluvial, and tectonic geomorphology analysis to better define the main phases of the landscape evolution and the impact of morphoneotectonic processes on fluvial environments in uplifting piedmont areas.
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In tectonically active regions, many aspects of the topography can provide clues to morphotectonic development. Morphological lineaments have varying degrees of reliability as indicators of neotectonic movement. Here, eleven lines of evidence are assessed and combined for the Podtatranská Kotlina Basin (PtK) between the Tatra and Low Tatra (Nízke Tatry) Mountains, the highest topography of the Western Carpathians. This permits identification of the configuration of structural-neotectonic blocks and documentation of their behaviour. Specifically we 1) evaluate the reliability of fault mapping results, 2) assess relative uplift and subsidence accommodated by the faults, 3) evaluate the intensity of fault movement and 4) explore the role of fault movement in the tilting of blocks. We define 358 structural-neotectonic blocks in the PtK region, providing an exceptionally detailed morphotectonic analysis. Distinction of two stages of neotectonic uplift provides explanation of the regional discrepancy between intensive neotectonic activity and limited recent seismicity with Mw < 5. The first stage, in the Pliocene-Early Pleistocene, was characterized by isostatic uplift linked to delamination and/or convective removal of an over-thickened lithosphere. The second stage during the Late Quaternary involved more complex uplift, including the probable influence of episodic mantle flow induced by the load of the Scandinavian Ice Sheet on northern Europe. This resulted in a change in the extension and configuration of structural-neotectonic blocks, the movements of the Tatra block now measured by GNSS, and the interaction of neotectonic activity with effects of glacial–interglacial transitions.
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The Qingchuan Fault (QCF) is the main fault of the northeastern segment of the Longmenshan Fault zone (LMSFZ) on the eastern Tibetan Plateau boundary. The QCF accommodates ongoing deformation in the eastern Tibetan Plateau; however, its fault motion and potential seismic risk are still debated. This study combines a systematic analysis of deflected stream channels along the fault using 10-m digital elevation models with field investigations and measurements of the cosmogenic ¹⁰Be-derived erosion rates. The degree of channel deflection due to the interaction between strike-slip motion and channel growth processes is analyzed, followed by a quantitative extraction of the actual tectonic offsets and a calculation of the erosion rates. The long-term average strike-slip rates calculated from channel offsets range from 0.4 ± 0.1 to 1.7 ± 0.1 mm/a along the fault, with those in the southwestern section lower than those in the central section. Such differences may be attributed to slip partitioning of the northeastern extension of the Yingxiu–Beichuan Fault. In addition, analysis of stream longitudinal profiles and along-fault topographic variations illustrate that the small thrust component of the QCF decreases to the northeast, and a minor normal component exists at its northeastern end. The distributions of strike-slip and vertical-slip motions of the QCF indicate that fault slip of the central LMSFZ propagates to the northeast across the Minshan uplift and continues to slip along the QCF. Moreover, thrusting of the southern-central segment of the LMSFZ and dextral strike-slip faulting of the QCF may both accommodate complex deformation related to eastward expansion of the Tibetan Plateau. Our results support the model of rigid block extrusion associated with slip partitioning along tectonic boundary faults. These findings have implications for constraining potential seismic hazards and understanding the geodynamic mechanisms of the eastern Tibetan Plateau.
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The present conditions of the Dittaino River were investigated by using tools addressing different components of the IDRAIM (stream hydro-morphological evaluation, analysis, and monitoring system) procedure. After the segmentation of the river, the Morphological Quality Index (MQI) and the Morphological Dynamic Index (MDI) were assessed to analyze its morphological quality and to classify the degree of channel dynamics related to progressive changes occurring in the relative long-term (i.e., 50–100 years), respectively. The results show that 45% and 22% of the analyzed reaches (mainly located in highest zones of the hydrographic network) were, respectively, of high and good quality. The MQI class decreased to good and then to moderate in the downstream direction, and two reaches were of poor class. The highest MDI classes were also mainly identified in the highest zones of the hydrographic network. Some limitations (i.e., the elevated number of indicators, as well as their simplification) and strengths (i.e., the easy applicability to a large number of reaches) were identified during the application of the MQI method to the Dittaino River.
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