Search Results (14)

The spatial variability of input parameters plays a crucial role in the interpretation of geomorphic indices, with digital elevation models (DEMs) being the primary data source. However, the influence of DEM resolution on these indices has rarely been investigated. This study investigated the influence of DEM resolution on the assessment of tectonic activity using the normalized stream length–gradient (SLk) index, which reflects variations along river profiles. The SLk index is sensitive to changes in river gradients that may result from active faulting or differential uplift, making it a valuable tool for identifying zones of active tectonic deformation. Therefore, understanding the impact of DEM resolution on SLk analysis is critical for accurately detecting and interpreting subtle tectonic signals, particularly in intraplate regions where deformation is slow and geomorphic expressions are faint and discontinuous. By comparing high-resolution LiDAR-derived DEMs (L-DEMs) and low-resolution topographic map-derived DEMs (T-DEMs), we analyzed the SLk index distributions along the Yangsan Fault, Korean Peninsula, an intraplate setting with Quaternary activity. According to the results, SLk anomalies derived from L-DEMs had a continuous distribution along the fault, closely aligning with known surface ruptures and indicating active tectonic deformation. In contrast, SLk anomalies derived from T-DEMs were sporadic and less continuous, especially in low-relief landscapes such as alluvial fans and floodplains, highlighting the limitations of T-DEMs in detecting fault-related features. High-resolution DEMs were better able to capture finer-scale geomorphic features, such as fault scarps, deflected streams, and lineaments associated with active tectonics, providing a more comprehensive view of fault-related deformation. This discrepancy highlights the importance of resolution choice in tectonic assessments, as low-resolution DEMs may underestimate the tectonic activities of intraplate faults by missing subtle topographic variations. While the choice of DEM resolution may depend on study area, scope, and data availability, high-resolution DEMs are critical for identifying tectonic activity in intraplate regions where geomorphic features of faulting due to slow deformation are subtle and dispersed. Full article

Fault segmentation plays a critical role in assessing seismic hazards, particularly in tectonically complex regions. The Laji-Jishi Shan Fault Zone (LJSFZ), located on the northeastern margin of the Tibetan Plateau, is a key structure that accommodates regional tectonic stress. This study integrates geomorphic indices, cross-fault deformation rate profiles, and 3D crustal electrical structure data to analyze the varying levels of tectonic activity across different segments of the LJSFZ. We extracted 160 drainage basins along the strike of the LJSFZ from a 30 m resolution digital elevation model and calculated geomorphic indices, including the hypsometric integral (HI), stream length-gradient index (SL), and channel steepness index (k_sn), to assess the variations in tectonic activity intensity along the strike of the LJSFZ. The basins were categorized based on river flow directions to capture potential differences across the fault zone. Our results show that the eastern basins of the LJSFZ exhibit the strongest tectonic activity, demonstrated by significantly higher SL and k_sn values compared to other regions. A detailed segmentation analysis along the northern Laji Shan Fault and eastern Jishi Shan Fault identified distinct fault segments characterized by variations in SL and k_sn indices. Segments with high SL values (>500) correspond to higher crustal uplift rates (~3 mm/year), while segments with lower SL values exhibit lower uplift rates (~2 mm/year), as confirmed by cross-fault deformation profiles derived from GNSS and InSAR data. This correlation demonstrates that geomorphic indices effectively reflect fault activity intensity. Additionally, 3D crustal electrical structure data further indicate that highly conductive mid- to lower-crustal materials originating from the interior of the Tibetan Plateau are obstructed at segment L3 of the LJSFZ. This obstruction leads to localized intense uplift and enhanced fault activity. These findings suggest that while the regional stress–strain pattern of the northeastern Tibetan Plateau is the primary driver of the segmented activity along the Laji-Jishi Shan belt, the direction of localized crustal flow is a critical factor influencing fault activity segmentation. Full article

The present study aims to assess the tectonic activity in the South Setifian allochthonous complex, providing insights into the evolution of the landscape. A morphometric analysis of Jebel Youcef Mountain (JYM) in Eastern Algeria was conducted to assess neotectonic activity. Six quantitative parameters were analyzed: stream length-gradient index, asymmetric factor, hypsometric integral, valley floor width-to-valley height ratio, index of drainage basin shape, and index of mountain front sinuosity across the 16 river basins in the region. The geomorphic indices are combined into a single index of relative tectonic activity (IRTA), categorized into four classes: very high, high, moderate, and low. The results identified two major lineament sets. The NE-SW lineament set is the dominant structural feature, playing a key role in driving recent geological processes and deformation in the study area. In contrast, the E-W and NW-SE lineament sets exert a more localized influence, primarily affecting the Jurassic formations at Kef El Ahmar’s central peak in Jebel Youcef, though they exhibit relatively lower tectonic activity compared to the NE-SW lineament set. Based on the relative active tectonic classes, significant neotectonic activity is evident in the study area, as shown by distinctive basement fracturing. The findings contribute to understanding the structural processes in the study area. Furthermore, the study establishes a systematic framework for analyzing tectonic activity and landscape morphology evolution, enhancing our perception of the convergence between the North African Alpine zones and the Atlas range. Full article

This work used an analysis of the geomorphic indices to effectively assess the relative tectonic activity of a Red Sea coastal region in Saudi Arabia between Al Farrah and Heelan. This approach is useful in examining topographical and geomorphological signatures in different landscapes. Through a detailed investigation of geomorphic indices, the study basin’s active and inactive characteristics may be observed and distinguished. The applied indices include a rock strength index, stream length gradient index, hypsometric integral index, drainage basin analysis index, mountain front sinuosity index, and valley floor width-to-valley floor height ratio index. The results obtained from this study are discussed and presented as a unique index of relative tectonic activity (Rta), which is divided into three different classes: low, moderate, and high tectonic activity. There have been few studies of active tectonics in the study basin along Saudi Arabia’s eastern Red Sea coast, making it an excellent choice to evaluate and simulate the relative activity based on large-scale basin analysis. The study basin exhibits variable classes of tectonic activity resulting from the Red Sea extension event. The idea that areas with anticipated relatively high rates of tectonic activity are coupled with indicators of Rta index values is examined in this study. Full article

In this paper, we state the usefulness of geomorphic analysis, typically applied to highly deformed landforms, to investigate the tectonic geomorphology of an intercontinental structure: the Fatima suture zone. The Fatima suture zone (FSZ) landscape is a tectonically distinct deformation zone along the eastern coast of the Red Sea in western Saudi Arabia providing a complex zone in terms of geology, tectonics, and geomorphology. This zone presents many deformations and fault reactivations that were produced from the effect of horizontal, vertical, and thrust motions as well as deposition and erosion processes. Through several morphometric analyses, remotely sensed data, and geospatial techniques, we recognized the detailed geomorphic surface features of the Fatima suture zone region. Morphometric indices applied in this paper include the stream length gradient index (SL), basin asymmetry factor index (Af), hypsometric integral index (Hi), valley floor width to valley floor height ratio index (Vf), basin shape index (Bs), and mountain front sinuosity index (Smf). Every single morphometric index provides three different relative tectonic classes based on the assigned value ranges. The overall results obtained from the analysis were averaged and presented as an indicator index namely the relative seismic activity (RSA) index, which was classified into four distinct classes from relatively very high to low seismic activity: class 1 is very high seismic activity (CA ≤ 1.5); class 2 is high seismic activity (1.5 < CA ≤ 2); class 3 is moderate seismic activity (2 < CA ≤ 2.5); and class 4 is low seismic activity (CA > 2.5). Additionally, a combination of the two indices (Smf and Vf) was presented as a quantitative model of the relative seismic activity of the examined mountain fronts. The results of the RSA index provided signatures of all four classes of the study region. Two-thirds of the total area of the study region were recorded as high to very high classes in terms of seismic activity. The paper finally concludes that this integration method allows assessment and evaluation of the highly deformed landscapes related to active tectonism. Despite the impact of the Fatima suture zone providing low to medium activities in some parts, it has a signature control on the recent landscape evolution. Full article

The response of the stream geomorphic index to fault activity is important for assessing the regional seismic hazard. The data used in this paper are 12 m resolution TanDEM-X data. The Fill tool in the Hydrology toolset in ArcGIS 10.5 was used to first process the digital elevation model (DEM), then analyse the flow direction of the DEM after filling and finally extract streams with catchment areas of more than 9 km². Based on the DEM spatial analysis, the stream geomorphic index of the Lianfeng–Ningnan segment (LNS) of the Lianfeng fault was extracted, including the stream length gradient (SL) and the hypsometric integral (HI). This information, combined with the analysis of typical field geomorphology and terrace profiles, was used to define the fault activity period. To analyse the activity characteristics of the LNS, the LNS was divided into northern (Lianfeng to Jinyang), middle (Jinyang to Duiping town) and southern segments (Duiping town to Ningnan). The stream geomorphic index showed spatial variations, with mean SL and HI values of 384 and 0.45, respectively, in the northern segment; 175 and 0.41, respectively, in the middle segment; and 378 and 0.45, respectively, in the southern segment. These results indicate that the northern and southern segments of the LNS are more active than the middle segment, that there is little difference between the northern and southern segments, and that the activity of the middle segment is relatively weak. By comprehensively analysing the lithology, climate and tectonics in the LNS region, we conclude that tectonics are the main factor controlling the stream geomorphology in the LNS region. Based on this information and the analysis and dating of field geomorphology and terrace profiles, we found that the Lianfeng fault was active in the Holocene, which is consistent with the latest research results. Full article

The objective of this study was to assess the performance of form-based and process-based models, and of local-scale and reach-scale models, used to examine bank retreat and sediment transport in stream restoration. The evaluated models were the Bank Erosion Hazard Index (BEHI), Bank Assessment for Nonpoint Source Consequences of Sediment (BANCS), Bank Stability and Toe Erosion Model (BSTEM), and HEC River Analysis System (HEC-RAS 1D). Model-to-model assessments were conducted to quantify the impact of model selection when predicting applied stress and geomorphic change in a restored stream in North Carolina, USA. Results indicated that the mobility of the bed dictated model selection at the reach-scale. The process-based HEC-RAS 1D was needed to accurately analyze the sand-bed stream, predicting amounts of geomorphic change comparable to measured data and up to three orders of magnitude higher than those from local-scale models. At the local-scale, results indicated that the bank retreat mechanism and flow variability constrained model selection. The form-based BEHI and BANCS did not directly account for geotechnical failure nor capture severe floods, underpredicting amounts of geomorphic change by an order of magnitude when compared to the process-based BSTEM, and failing to characterize erosion potential and applied stresses after short-term morphodynamic adjustments. Full article

Based on a digital elevation model (DEM) and GIS technology, we extracted and analyzed stream geomorphic indices—such as the slope, relief degree of the land surface (RDLS), hypsometric integral (HI) and channel steepness index (k_sn)—of the Cangshan Piedmont Fault, Fengyi–Dingxiling Fault and Midu Basin Margin Fault in the northern segment of the Red River Fault Zone. This work indicates that all the stream geomorphic indices show higher values, with the highest values along the Cangshan Piedmont Fault, followed by the Fengyi–Dingxiling Fault, and the lowest values along the Midu Basin Margin Fault, forming a decreasing trend from north to south. Based on lithology, climate and tectonics, we infer that neotectonic activity is the main factor controlling the development of the drainage geomorphology. The results show that the northern segment of the Red River Fault Zone is highly active and that the activity level shows a decreasing trend from north to south. The results of this study are consistent with previous conclusions that the overall activity of the Red River Fault Zone weakens from north to south, and the activity in the northern segment has been the most intense since the Late Pleistocene. Full article

Drainage divide is a dynamic feature that migrates in response to tectonic activity. The asymmetric uplift between two adjacent basins causes the divide migration from a slower to faster uplift area. Sado Island, Japan, has been affected by southeastward tilting uplift for ca. 300k years. Despite the faster uplift on the northwest, the main divides have existed on the southeast side of the geometric center of the island, with no other feature suggesting tectonic inversion of the tilting direction. In this study, we conducted a digital elevation model (DEM) based investigation that focused on divide migration. A spectrum from very inactive to active divide migration in the northwest. Regardless of their position, actively migrating divides are comprehensible, but inactive divides located in a relatively slow uplift area remain unclear. We concluded that some divides slowed down owing to the local balance of erosion rates across the divides, which does not imply balance between uplift and river erosion at the basin scale, reflecting disequilibrium in river longitudinal profiles. The main divides of Sado have presumably continued to slowly migrate toward the area of faster uplift; however, they are most likely to have never overcome the moving geometric center owing to land expansion at the seacoast due to asymmetric uplift. Full article

The Gulf of Suez area represents one of the most famous tectonic structures in the Red Sea, with a long history of low-, moderate-, and high-intensity earthquakes. This paper provides geomorphic analytics of the fault-initiated mountain front sinuosity (S_mf) and the stream gradients that cross various segments of the fault scarps. The results from the mountain front sinuosity index (S_mf) and the valley floor width to valley height ratio index (V_f) suggest different levels of activities along the different fault segments. The analysis of the stream gradient index reflects that streams running through the fault segments mostly have higher river gradient values identified by knickpoint spots. With regard to the strike variation in the mountain front sinuosity, valley floor width to valley height ratio, and stream river gradients, the results are compatible with the predominant mountain front’s relief. Finally, the calculated geomorphic results show that the eastern segments might reflect higher seismic signals with respect to the central and western segments of the entire Wadi Araba basin. Thus, more careful studies are required to investigate seismic hazard possibilities. Full article

Endorheic rivers as landlocked systems with no hydrological connections to marine environments are suffering from water and ecosystem crisis worldwide, yet little is known about their structural characteristics with complex geomorphic and climatic dependence. Based on the river networks identified from 30 m resolution digital elevation models and surface water dynamic information derived from Landsat images, we investigate the hierarchical characteristics of 60 sub-basins in the Tarim Basin, the largest endorheic river basin in China. In the Tarim River basin, endorheic rivers exhibit a self-similarity only in the range of stream-orders 1–4, compared to the range of stream-orders 1–5 observed in exorheic rivers, owning to the limited stream power to maintain the similar aggregation of rivers in the arid regions. Moreover, the Tarim River networks demonstrate lower bifurcation ratio (2.48), length ratio (2.03), fractal dimension (1.38), and drainage density (0.24 km⁻¹) in representative sub-basins, with a significant decay in median values compared with those derived from exohreic rivers at similar scales, suggesting sparser and imperfect developed branching river networks in endorheic basins. Further analysis on the Tarim reveals that endorheic river structure is more related to glacier extent (r = 0.67~0.84), potential evapotranspiration (r = 0.63~0.81), and groundwater type index (r = 0.64~0.73), which is essentially different from the structure of exorheic river represented by the Yellow River largely controlled by surface runoff, precipitation, and vegetation coverage. This study stresses the differences in intrinsic structural characteristics and extrinsic drivers of endorheic and exorheic rivers and highlights the necessity of differentiated strategies for endorheic river management in fragile ecosystems. Full article

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. Full article

The Himalayan main frontal thrust (MFT) accommodates most of the present-day Indo–Asia convergence with related periodic earthquakes. The seismicity and deformation mechanism varies considerably across the frontal Himalayas. We mapped a segment (Manzai Ranges) of the MFT at the western margin of the Himalayas and analyzed its deformation mechanism and active tectonics using geomorphic indices and the Interferometric Synthetic Aperture Radar (InSAR) Small Baseline Subset (SBAS) technique. Two frontal thrust faults (Khirgi and Jandola) were mapped using Sentinel-2B band ratios in the study area. Water gaps were present in the form of deflected streams at the tip of the growing anticlines. The C-band RADAR interferometry (Sentinel-1A) showed an average uplift of 5–9 mm/year in the satellite line of sight (LOS) from May 2018 to October 2019. The velocity profiles show an uplift variation across the anticlines and may be related to the displacement transfer from the zone of compression in the Manzai Ranges to the zone of transpression in the Pezu–Bhittani Ranges. Four types of morphometric analyses were carried out to assess the relative tectonic activity, namely mountain front sinuosity index (Smf), valley floor width to height ratio (V_f), normalized longitudinal river profile, and normalized channel steepness index (Ksn). The landscape response to active tectonics in the study area was recorded as a deep fluvial incision in V-shaped valleys, convex river profiles, topographic breaks as knickpoints, and a high Ksn index. The geomorphic parameters show a relative increase in tectonic uplift and deformation from the Kundi anticline to the Khirgi and Manzai anticline. We concluded that the frontal structures in the western Himalayas are still going through an active phase of deformation and landscape development with both seismic and aseismic creep. Full article

In some states, the Stream Quantification Tool (SQT) has been adopted to quantify functional change of stream mitigation efforts. However, the ability of the SQT protocol to predict biological function and uphold the premise of the Stream Functions Pyramid (Pyramid) remains untested. Macroinvertebrate community metrics in 34 headwater streams in Piedmont, North Carolina (NC, USA) were related to NC SQT protocol (version 3.0) factors and other variables relevant to ecological function. Three statistical models, including stepwise, lasso, and ridge regression were used to predict the NC Biotic Index (NCBI) and Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness using two datasets: 21 SQT variables and the SQT variables plus 13 additional watershed, hydraulic, geomorphic, and physicochemical variables. Cross-validation revealed that stepwise and ridge outperformed lasso, and that the SQT variables can reasonably predict biology metrics (R² 0.53–0.64). Additional variables improved prediction (R² 0.70–0.88), suggesting that the SQT protocol is lacking metrics important to macroinvertebrates. Results moderately support the Pyramid: highly predictive ridge models included metrics from all levels, while highly predictive stepwise models included metrics from higher levels, and not watershed hydrology. Reach-scale metrics were more important than watershed hydrology, providing encouragement for projects limited by watershed condition. Full article