Stream Length Gradient Research Articles

GIS-based analysis of the Stream Length-Gradient Index for evaluating effects of active tectonics: a case study of Enfidha (North-East of Tunisia)

Our study aims at calculating morphometric indices through the recourse to the Digital Elevation Model (DEM) and its attributes (hydrographic networks, watersheds, and reliefs). This quantitative measurement is used for the morphotectonical analysis of the Enfidha area (North-East of Tunisia) in the GIS environment and statistical platform. The Enfidha area is selected to analyze and identify neotectonic morphostructures on basis of the morphological evolution of the landscape. The coastal Enfidha plain is part of the Tunisian Sahel that is marked by its instability and frequent earthquakes that prove the presence of the recent deformation and active subsurface faults. This morphometric modeling in the geological investigation area reflects the morphotectonic spatial evolution in the Quaternary basins areas. Stream length (SL) proposed by Hack (1973) and denominated by Etchebehere et al. (2004) Revista do Instituto de Geociencias USP, Serie Cientifica, Sao Paulo 4(2):43–56 as the RDE index (Relation Declivity Extension) was used for application in the studies of neotectonic approach. RDE index is one of the morphotectonical indices that designates the tectonics anomalies in rivers. The variability in (RDE) values can indicate both a lithology resistance towards erosion and major active subsurface faults or low slope. Our geostatistical method is required to obtain RDE index maps based on lithological filtrations and value interpolations which are calculated in a drainage line network. This method calculates, measures, and validates spatial distribution of hack RDE index through a high statistical accuracy in a quantitative anomalies study. The RDE anomaly maps of the study area mirror the concurrence between anomaly zones, major active subsurface E-W faults, and local geological discontinuities related to neotectonical activities that affect the hydrographic network. This study proves that the RDE index can be especially used to detect the influence of active large-scale faults on the landscape evolution.

Morphotectonics in a low tectonic rate area: Analysis of the southern Portuguese Atlantic coastal region

South Portugal is characterized by low tectonic rates (<0.3 mm/a), with infrequent large seismicity. Recent studies indicate a coastal region in southwest Portugal uplifting at higher rates (0.11 ± 0.01 mm/a) than the remaining southern portion of Portugal (~0.04 mm/a); however, the mechanisms that drive this uplift are poorly understood. With the purpose of investigating the regional Quaternary deformation and its patterns, as well as the difference in the uplift rate, 77 exorheic drainage basins along 460 km of the southern Portuguese coastline were analysed through the application of geomorphic indices. In this study we applied stream channel sinuosity S, basin relief ratio Rh, elongation Re, basin shape ratio Bs, valley height-width ratio Vf, basin asymmetry factor AF, hypsometry HI and, the stream-length gradient index SL, and we propose the terminal basin shape index TBS. This study aims to (1) identify Quaternary deformation along presumed tectonic structures; (2) recognize uplift or subsidence along the coastline; and (3) test the application of geomorphic indices in low deformation rate environments. The cross-correlation of results led to the recognition of the São Teotónio-Aljezur-Sinceira fault system and the São Marcos-Quarteira Fault as major regional Quaternary faults, as well as to the interpretation of Quaternary activity for other structures. Spatial differences in uplift rates are identified through basin shape indices and valley height-width ratios, even for low vertical motion rates, whereas other indices were found to be not as sensitive to variations in uplift rate.

Morphodynamics of the Kulsi River Basin in the northern front of Shillong Plateau: Exhibiting episodic inundation and channel migration

The present study is undertaken in the Kulsi River valley, a tributary of the Brahmaputra River that drains through the tectonically active Shillong Plateau in northeast India. Based on the fluvial geomorphic parameters and Landsat satellite images, it has been observed that the Kulsi River migrated 0.7–2 km westward in its middle course in the past 30 years. Geomorphic parameters such as longitudinal profile analysis, stream length gradient index (SL), ratio of valley floor width to valley height (Vf), steepness index ( $$k_{s})$$ indicate that the upstream segment of the Kulsi River is tectonically more active than the downstream segment which is ascribed to the tectonic activities along the Guwahati Fault. $$^{14}\hbox {C}$$ ages obtained from the submerged tree trunks of the Chandubi Lake, which is located in the central part of the Kulsi River catchment suggests inundation (high lake levels) during 160 ± 50 AD, 970 ± 50 AD, 1190 ± 80 AD and 1520 ± 30 AD, respectively. These periods broadly coincide with the late Holocene strengthened Indian Summer Monsoon (ISM), Medieval Warm Period (MWP) and the early part of the Little Ice Age (LIA). The debris which clogged the course of the river in the vicinity of the Chandubi Lake is attributed to tectonically induced increase in sediment supply during high magnitude flooding events.

Geomorphic evidence for active tectonic deformation in the coastal part of Eastern Black Sea, Eastern Pontides, Turkey

ABSTRACTThe Eastern Pontides (EP), which is the under transpressional deformation zone, is an active mountain belt that has been rising rapidly since the Cenozoic era because of the Arabian-Eurasian convergence. Morphometric studies have been performed to investigate the tectonic activity of this region and better understand the characteristics of the faults geomorphologically; the faults control the mountain fronts in the drainage basin of the EP. The results show the Hypsometric Curve (HC)-Hypsometric Integral (0.37-HI-0.67), Basin-Shaped Analysis (1.2-Bs-7), Valley-Floor-Width to Height-Ratio (0.4-Vf-1.2) and Asymmetry Factor (35-AF-81) applied to 46 drainage basins together with 9 tectonically controlled geomorphic indices (1.2-Smf-1.5) and a Stream Length Gradient (30-SL-120) indicate that the EP is tectonically active, and when the areas are evaluated according to Smf and Vf analyses, the tectonic level is relatively high. According to our conceptual model for the uplifting of the EP, with respect to field studies and morphometric analysis, (i) the EP is the active deformation zone and has a “push-up” geometry in conjunction with the North Anatolian Fault; (ii) the EP is progressively uplifting at a rate of more than 0.5 mm/yr in along with the thrust faults of the Black Sea Fault (BSF) and Borjomi-Kazbegi Fault (BKF).

Morphology and channel characteristics of an equatorial tropical river in Malaysian Borneo: a detailed evaluation through spatially explicit geomorphometric modelling

Geomorphic and morphodynamic characteristics of Akah River in Sarawak, Malaysia in north-western Borneo were modelled using geographical information system assisted techniques and geomorphometric indices. Stream properties such as longitudinal profile, stream length gradient index (SL), channel slope, hypsometric curve, hypsometric integral, sinuosity index and channel cross profiles were analyzed. Morphological features such as meander and channel bar characteristics were evaluated and compared to classify the river and to identify the processes responsible for its present nature. The longitudinal profile, SL index and channel slope indicate the presence of multiple knick points in the channel, which may be indicative of changes in the base level characteristics of the river or lithological differences. The characteristic convex shape of hypsometric toe indicates late stage of deposition due to diffusive processes and the hypsometric integral identifies the geomorphic evolution as in the advanced stage i.e. erosion is significant. The sinuosity index classifies the entire river as meandering and some segments as tortuously meandering with varied stream valleys. Numerous channel bars of various dimensions are found in different reaches of the stream indicating varying channel bottom characteristics and flow mechanism due to the influence of geological process. The information generated from spatial modelling of different geomorphic indices (different terrain variables) and channel characteristics classifies the Akah subwatershed with slope (diffusive) and fluvial dominated geomorphic process having highly meandering channel and showing anomalous characteristics in some segments. These findings will serve as baseline information, while considering the region for hydrological development activities which include check dams, mini hydroelectric projects.

Tectonic Geomorphology in Parts of Koyna Region, Maharashtra

ABSTRACT Geomorphic signatures in parts of Koyna region were analysed using satellite images and morphometric indices (stream length gradient index and valley width to height ratio) with limited field checks in key areas for understanding the role of tectonics in this seismically active zone. The Koyna River zone, particularly downstream of Koyna dam wall up to Kajali Nadi, is characterised by incised narrow valleys, steep escarpments and structurally controlled drainage. Presence of knick points at consistent elevations between 825 m to 675 m, steep gradients in an otherwise gradual longitudinal profile and valley width to height ratio less than 1.0 suggest readjustment of the streams along NW-SE and N-S directions. The escarpment slopes in general have en echelon arcuate ridge pattern ∼ N45°-N 225° in the western part, and then becomes ∼N 10°-N 190° near Donachiwadi, almost orthogonal to the E-W Koyna River. The Donachiwadi fault runs parallel to the escarpment slopes observed near Kodoli. The fluvial system in Koyna thus indicates rejuvenation controlled by basement propagated structures.

Morphotectonic analysis and GNSS observations for assessment of relative tectonic activity in Alaknanda basin of Garhwal Himalaya, India

Alaknanda basin in the Garhwal Himalaya, India, is a tectonically active region owing to ongoing crustal deformation, erosion, and depositional processes active in the region. Active tectonics in this region have greatly affected the drainage system and geomorphic expression of topography and provide an ideal natural set up to investigate the influence of tectonic activity resulting from the India-Eurasia collision. We evaluated active tectonics by using high resolution digital elevation model (DEM) based on eight geomorphic indices (stream length gradient index, valley floor width-to-height ratio, hypsometric integral, drainage basin asymmetry, transverse topography symmetry factor, mountain front sinousity index, bifurcation ratio, and basin shape index) and seismicity in eight subbasins of Alaknanda basin. The integrated product, relative tectonic activity index (TAI) map, was classified into three classes such as: ‘highly active’ with values ranging up to 2.0; ‘moderately active’ with values ranging from 2.0 to 2.25; and ‘less active’ with values >2.25. Further, the results were compared with relatively high crustal movement rate of 41.10mm/y computed through high precession Global Navigation Satellite System (GNSS) based continuous operating reference station (CORS) data. Thus, we concluded that this new quantitative approach can be used for better characterization and assessment of active seismotectonic regions of the Himalaya and elsewhere.

Identification of deformation variability and active structures using geomorphic markers in the Nahan salient, NW Himalaya, India

The morphotectonic study was carried out in the Nahan salient, located between the well known Kangra and Dehradun recesses in western Himalaya, India. We used various geomorphic indices namely stream length gradient index (steepness index), Hack profile convexities, and hypsometric integral (HI) with hypsometric curve and elevation profiles to map the spatial variability in the tectonic process across the salient. Field observations and planform mapping of river terraces in the area support the morphometric data. We found a systematic variation of the gradient in long profiles (convexity) with numerous knickpoints in main rivers as well as their tributaries. The geomorphic processes responsible for anomalous behaviour in these fluvial indices also causes variability in the HI values for watersheds confined to different thrust sheets. We also carried out analysis of incision patterns in different river basins through variability in base level change, Topographic Ruggedness Index (TRI) and basin relief across the major thrust sheets. The western part of the Nahan salient area is relatively tectonically more active in comparison to the east. Further, fault(s) to the north of Main Frontal thrust (MFT) are undergoing more deformation than the MFT. We interpret this deformation as out-of-sequence activity in the Nahan salient. Integration of the geomorphic indices with field observations also helped us find new structure(s) that are necessary for the seismotectonic evaluation of the area.

Identifying active structures in the Chitwan Dun, Central Nepal, using longitudinal river profiles and SL index analysis

Previous studies have identified a seismic gap that has not witnessed any surface rupture earthquakes in the last 200–500 years located in the central sub-Himalaya (i.e., area around Chitwan intermontane valley). A higher rate of convergence in these parts poses a great threat of a surface rupturing earthquake in future. Recent analysis of the 2015 Gorkha earthquake to the north of this region suggests that it failed to rupture the surface; moreover, the stress is suggested to have transferred towards south. Therefore, the Chitwan intermontane valley - located in the sub-Himalaya of the central Himalayan seismic gap - is investigated in this study to identify the active structures. The longitudinal profile of a river considered to be one of the important geomorphic markers is used in this study for the identification of the active structures. The Hack profile and Stream-Length gradient index (SL index) is used to identify the anomalous segments of the rivers; these anomalous reaches are verified in the field for the presence of structures. Geomorphology of the region also supports the presence of active reverse faults in the valley. Abrupt break in the continuity of the geomorphic units and its correlation with the knick points and high SL index values indicate presence of around nine active structures in the Chitwan intermontane valley. Six new structures viz., Jharahi Thrust (JHT). Belani Thrust (BT), West Chitwan Thrust (WCT), Danda Thrust (DT), Central Churia Thrust 2 (CCT 2) and Shaktikhor Thrust (ST) have been identified in this study; whereas, three previously mapped structures viz., Main Boundary Thrust (MBT), Barakot Fault (BKF) and Central Churia Thrust (CCT) are also found to be active during the Quaternary/Holocene. Most of the newly identified structures appear to be splays of either the MBT or the CCT. These structures have displaced Quaternary landforms within the valley and are potentially active. The structures can get re-activated during large magnitude earthquake events in future.

Geomorphologic study of the valley floor in different tectonic segments along Kosi River valley between South Almora Thrust and Himalayan Frontal Thrust: Kumaun Himalaya, India

In the Kumaun Himalaya, a portion of the Kosi River valley of ~90 km in length is chosen to study the fluvial morphology that provides first‐order information about the dynamic response of bedrock channels to tectonic impulse. The Kosi River flows across/along major tectonic boundaries such as the South Almora Thrust, Ramgarh Thrust, Main Boundary Thrust, and the Himalayan Frontal Thrust, and local transverse and longitudinal faults. Varied fluvial landforms correspond to different tectonic settings, lithologies, bedrock channels, hillslopes, large landslides, terraces, and fans. The longitudinal valleys are also the sites for thick aggradational landforms. Some portion of these valleys fall in the areas of active extensional tectonics and is characterized by one of the widest valley floor sections in the Lesser Himalaya. In contrast, the transverse valley sections are incised by deep‐cut v‐shaped valleys and the narrowest valley section. Swerving of the Kosi River is observed in the Ramgarh Thrust and Amel Fault zones and also in the Main Boundary Thrust zone. Recent tectonic activity is evident from the presence of the faulted Quaternary deposits, linear fault scarps, abandoned channels, incised meandering, and multiple levels of terraces/strath terraces. Field observations and the computed ratio of valley floor width to valley height (Vf) corroborate each other. Valleys developed parallel to the strike of faults and bedrocks have relatively broader valleys with higher Vf values whereas in contrast, the valleys developed across the bedrock strike are narrow with smaller Vf values. The results of computed stream length gradient (SL) and steepness (Ks) indices show considerable correlations between the obtained SL and Ks data and the field evidences; high values of SL and Ks are characterized by the presence of knick points observed at the prominent thrusts and faults.

Morphometric analysis of relative tectonic activity in the Baturagung Mountain, Central Java, Indonesia

Special Region of Yogyakarta and Klaten district, Central Java is one of areas in Indonesia that is prone to earthquake caused by subduction in Indian Ocean and active fault in land. The earthquake sources from active fault probable from Opak and other faults located in Baturagung Mountain. Active faults controlling landform development in tectonically active regions, and it has significantly affected fluvial systems and mountain – front landscapes in the Baturagung Mountain. To assess tectonic activities in the area used quantitative analysis (morphometric). Morphometric analysis consists of 5 parameters geomorphic indices: drainage basin asymmetry (AF), hypsometric curve and integral (Hc and Hi), stream length gradient (SL) index, basin shape index (Bs), and mountain-front sinuosity (Smf). These indices were combined to yield the relative tectonic activity index (RTAI) using geographic information systems (GIS). The result found that RTAI in the study area are divided into three classes: Class 2 (high 0.6% of the watershed area (1.32 km2)); Class 3 (moderate 58.9% (122.1 km2)); and Class 4 (low 40.4% (83.75 km2)). All of morphometric analysis generally indicates this area more influenced by tectonics than erosion. The results are consistent with geomorphological observations.

Evaluation of relative tectonic activity of Buin Zahra-Avaj area, northern Iran

Present active tectonics is affecting central Alborz and created various dynamic landforms in Buin Zahra-Avaj area, northern Iran. The area, located between the southern central Alborz and the edge of northwestern central Iran, is the result of both the Arabian–Eurasian convergence and clockwise rotation of the south Caspian Basin with respect to Eurasia in which most of the steep fault planes have a left lateral strike-slip component and most of the dip-slip faults are reverse, dipping SW. Since this region consists of several residential and industrial areas and includes several fault zones, the assessment of the structures of the present activity is vital. Six significant morphometric indices have been applied for this evaluation including stream length–gradient (SL), drainage basin asymmetry factor (Af), hypsometric integral (Hi), ratio of valley floor width to valley height (Vf), drainage basin shape (Bs), and mountain front sinuosity (Smf). The combined analyzed indices, represented through the relative tectonic activity (Iat), were used. The study area was divided into four regions according to the values of Iat. These classes include class 1 (very high activity,18%), class 2 (high, 20%), class 3 (moderate, 44%), and class 4 (low, 18%). The results of these indices are consistent with field observations on landforms and the deformation of Quaternary deposits.

The role of climate and tectonics in aggradation and incision of the Indus River in the Ladakh Himalaya during the late Quaternary

AbstractThe geomorphic evolution of the upper Indus River that traverses across the southwest (SW) edge of Tibet, and the Ladakh and Zanskar ranges, was examined along a ~350-km-long stretch of its reaches. Based on the longitudinal river profile, stream length gradient index, and river/strath terraces, this stretch of the river is divided into four segments. Valley fill river terraces are ubiquitous, and strath terraces occur in the lower reaches where the Indus River cuts through deformed Indus Molasse. Optically stimulated luminescence ages of river/strath terraces suggest that valley aggradation occurred in three pulses, at ~52, ~28, and ~16 ka, and that these broadly coincide with periods of stronger SW Indian summer monsoon. Reconstructed longitudinal river profiles using strath terraces provide an upper limit on the bedrock and provide incision rates ranging from 1.0±0.3 to 2.2±0.9 mm/a. These results suggested that rapid uplift of the western syntaxes aided by uplift along the local faults led to the formation of strath terraces and increased fluvial incision rates along this stretch of the river.

Stream Length-gradient Hotspot and Cluster Analysis (SL-HCA) to fine-tune the detection and interpretation of knickzones on longitudinal profiles

This work presents a new approach for fine-tuning the analysis of stream longitudinal profiles. We show that applying Hotspot and Cluster Analysis (HCA), based on the Getis-Ord Gi* statistic, to the stream length-gradient (SL) index improves the visualization of anomalous values, assisting in the identification of tectonic structures and large landslides. High positive Gi* values indicate the clustering of SL anomalies (hotspots), and mirror the occurrence of knickzones on the stream long-profiles. We applied this methodology to a mountainous sector of the eastern Emilia-Romagna region, in northern Italy. Remote sensing and field surveys conducted on hotspot sites indicate that large landslides are the main process associated to over-steepened long-profile segments along streams connected to the valley slopes. Along-stream changes in bedrock resistance accounts for the main anomalies within sectors where hillslopes and valley floors are disconnected. We demonstrate that specific relationships between geometry and intensity of SL hotspots are indicative of the process responsible for the knickzone formation and, in particular that tectonic structures generally provide the longest and highest anomalies. The results of this work suggest that SL-HCA maps are more advantageous for detecting and interpreting knickzones compared with traditional SL maps, since: i) they need less input data to be computed, thus making them useful to investigate regions poorly covered by detailed geological data and/or where field surveys are difficult to be carried out and ii) the hotspot geometry can help discriminate the knickzones attributable to gravitational mass movements from litho-structural ones.

Application of Drainage Basin Morphotectonic Analysis for Assessment of Tectonic Activities over Two Regional Structures of the Northeast India

ABSTRACT The analysis of drainage basin morphotectonic indices is applied in assessment of the influence of tectonic activity on thirteen selected drainage basins of the streams having linear courses and flowing over two very prominent regional structures of northeast India, viz. the Belt of Schuppen and the Dauki fault. Such analysis has been made in order to assess the influence of tectonic activity of these structures on the morphology of the drainage basins of those streams. The different morphotectonic indices considered are: Basin elongation ratio, hypsometric integral, steepness index and profile concavity, drainage basin asymmetry, valley floor width to valley height ratio, longitudinal profiles, stream length gradient index and mountain front sinuosity. Results of the analysis of the morphotectonic indices of the drainage basins infer that morphology of both the streams and drainage basins have been influenced by the regional structures and the present tectonic status of these two structures varies from active to slightly active phase. No significant influence of lithology is seen in the distribution pattern of the anomalous knick points along the longitudinal profiles. The study also reveals that presently the state of tectonic activity is not uniform within the same regional structure and the Belt of Schuppen is relatively more active as compared to the Dauki fault.

River and basin morphometric indexes to detect tectonic activity: a case study of selected river basins in the South Indian Granulite Terrain (SIGT)

The effects and influence of tectonic processes on the Anjarakandy, Thalassery, Mahe, and Kuttiyadi watersheds and rivers of the South Indian Granulite Terrain in Kerala were examined to determine their spatial heterogeneity. Drainage basin asymmetry (Af), transverse topographic symmetry factor (T), hypsometric integral and curve (HI), longitudinal profile, stream length gradient index (SL), and stream concavity index (SCI) suggest heterogeneity in tectonic influence. Clusters of geomorphic anomalies in similar lithology rule out lithologic control on drainage development. However, the orientations of the drainage networks and predominant fractures/lineaments compare closely and reveal strong tectonic influence. Though the watersheds are considered to be in an advanced stage of erosion by the low HI (<30) and high values of SCI, variations in the shape of the hypsometric curves and differences in the SCI values indicate the different influence of tectonic process from watersheds in the north to the south. Among the watersheds, the Mahe and Kuttiyadi are more sensitive to tectonic processes than the Anjarakandy and Thalassery and indicate spatial heterogeneity in the influence of tectonic activity, confirming the grouping of watersheds based on structural and drainage patterns.

Transverse tectonic structural elements across Himalayan mountain front, eastern Arunachal Himalaya, India: Implication of superposed landform development on analysis of neotectonics

Structural and morphotectonic signatures in conjunction with the geomorphic indices are synthesised to trace the role of transverse tectonic features in shaping the landforms developed along the frontal part of the eastern Arunachal sub-Himalaya. Mountain front sinuosity (Smf) index values close to one are indicative of the active nature of the mountain front all along the eastern Arunachal Himalaya, which can be directly attributed to the regional uplift along the Himalayan Frontal Thrust (HFT). However, the mountain front is significantly sinusoidal around junctions between HFT/MBT (Main Boundary Thrust) and active transverse faults. The high values of stream length gradient (SL) and stream steepness (Ks) indices together with field evidence of fault scarps, offset of terraces, and deflection of streams are markers of neotectonic uplift along the thrusts and transverse faults. This reactivation of transverse faults has given rise to extensional basins leading to widening of the river courses, providing favourable sites for deposition of recent sediments. Tectonic interactions of these transverse faults with the Himalayan longitudinal thrusts (MBT/HFT) have segmented the mountain front marked with varying sinuosity. The net result is that a variety of tectonic landforms recognized along the mountain front can be tracked to the complex interactions among the transverse and longitudinal tectonic elements. Some distinctive examples are: in the eastern extremity of NE Himalaya across the Dibang River valley, the NW-SE trending mountain front is attenuated by the active Mishmi Thrust that has thrust the Mishmi crystalline complex directly over the alluvium of the Brahmaputra plains. The junction of the folded HFT and Mishmi Thrust shows a zone of brecciated and pulverized rocks along which transverse axial planar fracture cleavages exhibit neotectonic activities in a transverse fault zone coinciding with the Dibang River course. Similarly, the transverse faults cut the mountain front along the Sesseri, Siluk, Siku, Siang, Mingo, Sileng, Dikari, and Simen rivers. At some such junctions, landforms associated with the active right-lateral strike-slip faults are superposed over the earlier landforms formed by transverse normal faults. In addition to linear transverse features, we see evidence that the fold-thrust belt of the frontal part of the Arunachal Himalaya has also been affected by the neotectonically active NW-SE trending major fold known as the Siang antiform that again is aligned transverse to the mountain front. The folding of the HFT and MBT along this antiform has reshaped the landscape developed between its two western and eastern limbs running N-S and NW-SE, respectively. The transverse faults are parallel to the already reported deep-seated transverse seismogenic strike-slip fault. Therefore, a single take home message is that any true manifestation of the neotectonics and seismic hazard assessment in the Himalayan region must take into account the role of transverse tectonics.

Assessment of Relative Active Tectonics in the Bozgoush Basin (SW of Caspian Sea)

Geomorphic indices are useful tools for studying relative active tectonics of a specific area. In this study, the relative active tectonics of Bozgoush region (NW of Iran) has been investigated based on Geomorphic indices. The studied indexes include: the stream length-gradient (SL), hypsometric integral (Hi), the ratio of valley floor width to valley height (Vf), the shape of the drainage basin (Bs), the sinuosity of mountain front (Smf), asymmetric factor of drainage basin (Af) and transverse topographic symmetry factor (T). In the present study, gathered data from various morphometric indexes of six basins are aggregated, and their obtained result is provided as relative active tectonics of the region or Iat index that shows a proper illustration of the relative active tectonics of the mentioned region. In order to develop a correct analysis of the mentioned area, the AHP (analytic hierarchy process) model with a studied weight, the final overlapped layer of relative tectonics is prepared with applying coefficients. With the comprehensive field studies, evidences like deep valleys, river bed immigration, landslides, sudden change in river cycles and surfaces of faults were found that are in good consistence with obtained data of relative active tectonics of the region. After measuring these indexes, it was found that Aydoghmush and OujanChay basins have a high relative active tectonics. With regard to the obtained results of present study, it seems that Tabriz fault has the most seismic and motional potential in northern basins of the region. In addition, in Aydoghmush basin, in southern part of the region, Qeynarjehchartagh fault has a high active tectonics that according to the estimated values has been identified as an active young structure in the region.

Morphometric Analysis of Kakoi River Watershed for Study of Neotectonic Activity Using Geospatial Technology

Morphometric analysis is defined as the quantitative measurement of landscape shape. Morphometric studies of a watershed helps the researcher to compare different landform and calculate the geomorphic indices that may be useful for identifying a particular characteristic such as the level of neotectonic activity in a watershed. The present study has been carried out in Kakoi River Watershed which is a part of Lower Subansiri River Basin in Assam. The study area is geo-dynamically unstable region characterized by active faults, continuing crustal movements and complicated structural region which fall under the seismic zone V of India. In recent century, the Lower Suabsiri River Basin has gone tremendous morphological changes due to active tectonics activities. After the Assam Earthquake of 1950, some of the rivers like Subansiri and its tributaries Dirgha, Kadam and Kakoi suddenly changed their channels giving birth to new channels. The present study is to examine the neotectonic domains and the changes of river course. The geomorphic indices such as Hypsometric Integral (HI), Elongation ratio (Re), Asymmetry Factor (AF), Stream-length Gradient Index (SI), Mountain Front Sinuosity (Mfs), Basin shape index (Bs), Ratio of Valley floor width to Valley Height (Vf) and Channel sinuosity (S) etc. have been studied from remote sensing data. The results shows that the study area is under active tectonic area based on Vf (0.301), Rl (0.461), Bs (3.6), Sl (165.73) and other parameters such as S (1.38) and Mfs (2.02) indicated as moderate active tectonic region. Utilization of geospatial technology and remote sensing data in the present study becomes more reliable and helpful in analyzing, monitoring and understanding the landform changes in a watershed.

The application of geomorphic indices in terrain analysis for ground engineering practice

Terrain analysis studies for long linear engineering projects provide critical engineering geological and geomorphological data that inform project design options, route selection and construction methodologies. This paper introduces the use of geomorphic indices alongside methods of aerial photograph interpretation and remote sensing in the desk study phase of engineering terrain evaluations in the identification of landscape changes and geohazards in active tectonic regions. Three geomorphic indices (hypsometry, river long profile analysis and stream-length gradient index) are applied to freely available DEM data in order to develop the qualitative and quantitative (relative to study area) understanding of how the hillslope and river systems respond to the effects of tectonic activity and climate change. A hypothetical pre-feasibility study corridor (10km width) located in the Sorbas Basin (SE Spain) is used to develop the methods of application, which could represent a proposed rail, road or pipeline routing. The results of the scaled indices approach, from catchment to reach (i.e. section of uninterrupted river channel) investigations, indicate a variable response of landscape processes. ‘Active’ erosional conditions are found in the central and northern limits of the basin relating to a known zone of tectonic deformation, the Infierno-Marchalico Lineament, and also to the effects of a river capture-related base-level lowering. ‘Active’ conditions are typically linked to an increased occurrence of landslides and badland formation. ‘Stable’ conditions are more common in the west and east of the basin where drainage channels are effectively coupled to base level. The combined results of geomorphic indices and aerial photograph interpretation are used in the identification of engineering constraints and geohazards as related to gully development, badland formation and the formation of landslides. A simple geohazard constraints map is produced which demonstrates ground related hazard to the wider project team and can be used to target field investigations and further inform construction methodologies and limitations.