Stream-gradient Index Research Articles

Identification of morphostructures by utilizing Knickpoint Ranks, a method to avoid the camouflage effect in knickpoint analysis

Knickpoints are relief features characterized by a convex-up abrupt change in the equilibrium profile of a given river. In the field they can be recognized as rapids or waterfalls. Their presence indicate geological conditions or processes that modify erosive rates, such as contrasting lithologies, base-level changes, or active structures, and, therefore, especially relevant in tectonic geomorphology studies. The computation of knickpoints for classification purposes is made dividing the Slope-Extension Ratio (RDE) by the Total Slope-Extension Ratio (RDT), which are derived from the Stream-Gradient index (SL). Traditionally, the classification of knickpoints has been treated in two ways, (1) by the simple division into first and second order, according to a limit value of RDE/RDT of 10, and (2) by the statistical division of values into classes, mainly with natural breaks. Recent studies have used both divisions and correlated the RDE/RDT values with the size of the knickpoints in the field. However, there are studies on morphometric analysis that point to the existence of gaps that occur in specific cases, such as the so-called knickpoint camouflage. In order to eliminate these gaps and with the aim of improve the classification technique, we propose the determination of fixed intervals of distribution of knickpoints which, based on the division according to the RDE/RDT values, use the strengths of the statistical divisions as a means to define limits of RDE/RDT values. The objective of this methodological development is to prevent errors during the classifications as well as to facilitate the interpretation of the obtained knickpoints. The new classification method was applied in 20 hydrographic basins with their RDE/RDT values checked in 44 knickpoints in the field. The analyses carried out point to the coherence of the new proposed classification and confirm the effectiveness of both the fixed intervals and the tools used in the cartography of knickpoints.

Application of TOPSIS model in active tectonic prioritization: Madeira watershed, South America

The Andes orogenic belt is one of the most tectonically active zones located between the convergent margins of the South American plate and the Pacific plate. From the dissected western belt to the expanded alluvial plain of Amazon basin, the Madeira watershed bears recent tectonic imprints. The tectonic signature is well documented by the spatial and linear characteristics of the five sub watersheds along with the Madeira trunk river and channels. The level of tectonic activeness has been assessed on the sub watersheds of the Madeira River, which is one of the main right-hand tributaries of the Amazon River. On the five defined sub-watersheds and the main channel watershed of Madeira, several morphometric indices, viz., asymmetry factor (AF), tilt angle (β), sinuosity index (SI), channel concavity (ɵ), elongation ratio (Re), circularity ratio (Rc), transverse topographic symmetry factor (T) and basin shape index (Bs), have been used. To rank the watersheds based on tectonic activity, we applied the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) The active tectonics was also tested by a comparative study of linear indicators as Hack profiles, longitudinal profiles and segment-wise stream gradient index (SL) of watersheds 2 (rank 1) and 3 (rank 6). The results reveal that the most tectonically active watershed 2 is located in a high seismic magnitude zone with several deep earthquake epicenters. The least tectonically active watershed 6 is located in a low seismic zone.

Morphomertic and neotectonic study of Upper Teesta River basin, Sikkim Himalaya using geospatial techniques

This study is done on the basis of the surface and subsurface faults and active tectonic processes which disrupt the pattern of the drainage system present in the basin. The pattern of the drainages and their morphological features shown in the morphometric drainage basin areas which are used as a sign of neotectonics activity. This study is focused on the Upper Teesta River basin of the Sikkim Himalayan. For the study of the morphometric and morphotectonic analysis of the Upper Teesta River basin, ALOS PALSAR DEM was used to generate the drainage order of the basin with the help of the Arc GIS Software. The estimated drainage order of the basin is 6th. In this study, morphotectonic parameters such as asymmetry factor, elongation ratio, transverse topography asymmetry, mountain-front sinuosity, ratio of valley floor width to valley height, and hypsometric Integral was estimated 45.66, 0.55, 0.25, 1.08, 0.94, 0.44 respectively. These all-parameters value show the Upper Teesta River Basin is tectonically active. The stream gradient index of the basin was calculated >500 indicate the study region tectonically active. This research is validated using 50 years (1971–2020) earthquake data. Therefore, geospatial tool is an important tool to know the area is neo tectonically active.

Geospatial Analytics for Preliminarily Landscape Active Tectonic Assessment of the Wadi Araba Basin, Western Gulf of Suez, Egypt

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 (Smf) and the stream gradients that cross various segments of the fault scarps. The results from the mountain front sinuosity index (Smf) and the valley floor width to valley height ratio index (Vf) 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.

Tectonic Control of the Nanggulan Formation Based on Morphometric Analysis in Kulon Progo, Indonesia

DOI:10.17014/ijog.9.2.147-157Outcrop of Nanggulan Formation, surrounded by Old Andesite Formation (OAF) in the eastern part of Kulon Progo Dome, is very limited. Tectonic control is interpreted as a contributing factor. Tectonic activity can be shown by a morphometric aspect. The research purpose was to calculate the valley floor - valley height ratio, stream gradient index, and drainage density of Nanggulan and Old Andesite Formations. The method used is field survey and Shuttle Radar Topography Mission analysis. The field survey focused on Clumprit, Klepu, and Kalisonggo Rivers. The total number of valley segments for the Nanggulan Formation is 223 with the valley length of 4.62 km, while OAF is 101 with a valley length of 3.55 km. SRTM analysis showed that the valley segment in OAF was 55, and valley length was 1.48 km. The valley floor - valley height ratio measured in the Nanggulan Formation is ten valleys and OAF is eight valleys. In Nanggulan Formation, the valley floor - valley height ratio value is from 1.00 to 5.46 (low uplift), whilst in OAF, the results vary: as 1.35 to 4.58 (low uplift), 0.59 (medium uplift), and 0.43 (high uplift). The stream gradient index value of the Nanggulan Formation is 460.47 (medium tectonic), while OAF is 723.84 (high tectonic). The drainage density value of the Nanggulan Formation is 10.35 km/km2 (very smooth landscape texture) and OAF is 10.35 km/km2 (somewhat smooth landscape texture). Morphometry proves that Nanggulan Formation tectonic activity is more active, causing the Nanggulan Formation to be exposed to the surface.

Lithologic Controls on Geomorphic Evolution of the Central Western Ghats: An Example from the Aghnashini Catchment, Karnataka, India

Abstract In spite of the prolonged exposure and denudation (for >50 Ma), the catchments of the Western Ghats escarpment depict significant relief and rugged topography along the Indian passive margin. In this study, an endeavour has been made to comprehend the function of lithology in landscape dynamics of the Aghanashini catchment through quantitative geomorphology. Longitudinal profiles of this catchment demonstrate disequilibrium through anomalous high stream gradient index and normalized steepness index (ksn) that are related to topographic breaks. Correlation between lithology types and ksn inferred predominant lithologic control on drainage disequilibrium. Transformed coordinate (χ-plot) of the longitudinal profile explained the knickpoint dynamics in an extensive manner where the outcomes suggested river capture process, formation of steep gorge, and series of hanging waterfalls due to sudden change in boundary conditions. This study indicates strong lithologic control under the influence of intense precipitation on shifting knickpoints throughout the catchment area forcing to maintain the valley relief and hillslope angles responsible for rugged and high relief topography of Aghnashini catchment of the Western Ghats.

Tectonogeomorphic investigation of Kashmir Basin NW Himalaya

ABSTRACT The present study has been carried out in Kashmir Basin (KB), NW Himalaya, to determine the relative tectonic activity using morphotectonic analysis, drainage patterns, lineament analysis and geomorphological field observations. Geomorphic signatures in KB indicate that intrabasinal faults have been quite active during the Quaternary time and have played a dominant role in kinematic and structural evolution of the basin. The manifestation of this activity has been recorded by terrain morphology, uplifted river terraces, warped fluvial surfaces, strath surfaces, fault scarps, offset of Holocene sedimentary successions, braided, and offsetted drainage patterns and recent seismic activity in the region. Presence of active mountain fronts; concave, convex, and concavo-convex hypsometric curves; ambiguous stream gradient index and drainage basin asymmetry, elongated sub-basins clearly manifest tectonic influences in sculpting the basin geometry. The presence of NW-SE to NNE-SSW lineaments that generally strike parallel with the major regional tectonic structures (faults) clearly suggest intense deformation zones produced by ongoing regional tectonism. We propose that the techniques employed, the data obtained and the technical interpretations, are potentially useful and may also be extrapolated to similar tectonically active regions.

Cenozoic uplift of the Fátima Basin, NE Brazil

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 and 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.

Geomorphic Analysis, Morphometric-based Prioritization and Tectonic Implications in Chite Lui River, Northeast India

Abstract River morphometry is a useful approach in basin analysis which helps to interprets fluvially originated landforms. The aim of the present work is to evaluate the morphometric and morphotectonic parameters along with prioritization for soil erosion and water availability in Chite Lui watershed. Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is a useful approach to find out soil erosion and ground water potential zone with an aim to achieve successful management of a watershed. It helps to examine the susceptibility zone in watershed. The present paper documents the delineation of 14 sub-watersheds in Chite Lui River at 3rd order stream. Its prioritization has been performed using several morphometric parameters namely drainage density, elongation ratio and many other parameters using Analytical Hierarchical Process (AHP). Sub-watersheds are ranked from 1-14 based on soil erosion and groundwater potential zones. The Chite Lui watershed is a fifth order drainage basin with a total area of 52.7 km2. The tectonic parameters of the watershed as the asymmetry value is 34%, indicates the structural control over the area either by uplift or tilting. The hypsometric integral value is 0.5 and the valley width height ratio is 0.05 which also suggest tectonic activity in the area. Sinuosity related many parameters along with geomorphic indices like stream power index (SPI), stream gradient index (SL) and topographic wetness index (TWI) were also calculated to suggest the watershed health. The present paper shows that the morphometric analysis is highly relevant and efficient in delineating susceptibility zones.

Fluvial response to active tectonics: analysis of DEM-derived longitudinal profiles in the Rangit River Basin, Eastern Himalayas, India

The Himalayan Mountain Range has originated from the ongoing collision of the Eurasian and the Indo-Australian plates since the Paleogene. It is widely accepted that this tectonically-driven uplift is still continuing, as reflected by a large number of earthquakes in the area. Apart from the sub-surface and geophysical signatures, the surficial geomorphic markers deserve due attention. Fluvial systems, which preserve the evidence of the past and present tectonic perturbations on the surface, have often been investigated to assess the imprints of uplift in a region. Sensitive to long-term tectonic, structural and climatic regimes, the general forms of the longitudinal profile and its derivatives have been analysed across the globe for determining the varying roles of tectonics, litho-structure and climate. This article assesses the degree of tectonic and lithological control on the drainage network of the Rangit Basin in the Eastern Himalayas. One of the important characteristics of the studied basin is that the Main Central Thrust (MCT), which is located between the Greater Himalayas and the Lesser Himalayas, divides the basin into two distinct domains. Longitudinal profiles and their derivatives of 16 major tributaries of the Rangit River were extracted from the ALOS–PALSAR DEM and analysed. The controls on this Himalayan river were evaluated based on investigations of longitudinal profile shapes, stream gradient (SL) indices, longitudinal profile concavities and steepness. Prominent drainage anomalies such as above-grade conditions, exponential and linear fitting of longitudinal profiles, elevated values of SL indices, barbed drainage, over-steepened stream segments and fluvial hanging valleys imply rapid erosion rates in the basin. This is noticeable particularly in the lower domain of the Rangit Basin, especially in the areas located downstream of the MCT. A comparison of steep segments with the geological and lineament maps reveals that many of these anomalies are lineament-controlled. Furthermore, a large number of such features do not conform to lithological intersections, suggesting a possible tectonic factor behind the occurrence of such anomalies.

Evaluating the performance of multisource digital elevation models using morphometric parameters and field survey data over the mountainous landscapes of northwest Himalaya, India

In this study, seven morphometric characteristics were assessed from three freely available multisource DEMs and correlated with extensive field observations to assess the best-fit DEM over the mountainous landscapes of Kashmir Valley, northwest Himalaya, India. The morphometric parameters were assessed using 30 m ASTER GDEM v2 (ASTERDEM), SRTMDEM, and CartoDEM v3 R1 (CARTODEM) in the Ferozpora watershed of the Jhelum Basin, Kashmir Himalaya. Our findings indicated the closeness of mean bifurcation ratio (Rbm) values between manual digitization (Rbm = 4.12) and CARTODEM (Rbm = 4.07). The GPS-based values of drainage basin asymmetry, stream gradient index, basin relief, and longitudinal river profile also indicated a strong resemblance with CARTODEM-derived values. It is hence concluded that CARTODEM is the best-fit DEM representing the topographic and morphometric characteristics over the Kashmir region, however, the results from this analysis need to be tested and validated over larger geographic domains with contrasting lithological and topographic characteristics.

Quantitative Geomorphic Approach for Identifying Active Deformation in the Foreland Region of Central Indo-Nepal Himalaya

Globally the remote sensing and geomorphometric analysis are frequently used for the assessment of tectonic activity. We used satellite-driven DEM data to analyze regional scale fluvial landform development in the parts of the central section of the Indo-Nepal Himalayan mountain chain, which is attributed the active deformation along the strike of major thrust. This deformation is accompanied by coexisting river incision and base-level fall along the longitudinal river course. These anomalies are obtained through conventional geomorphic parameters namely, stream-gradient index (SL), and steepness index (Ks) along with a new method called river Gradient Length Anomaly (GLA) analysis. GLA is a lied to deduct surface uplift and subsidence at the intersection between drainage basin and active thrusts. The deviations (offset) occurred along the river course are attributed to long-term active tectonic movement along thrust/fault or because of erosion/sedimentation processes. We analyzed 16 south-flowing rivers (e.g. Sarda, Kauriala, Girwa, and Babai), across the major Himalayan thrusts such as Main Boundary Thrust (MBT), Ramgarh Thrust (RT) and Himalayan Frontal Fault (HFT). The computed values of SL along the longitudinal course of these rivers range between 0.9‒4153 and Ks ranges from 0.1 to 173. The anomalous rise of SL and Ks values close to the major thrust points toward ongoing tectonics in the basin. The estimated results of fault parameters show that the horizontal shortening is higher than the vertical uplift. The empirical relationship of slip rate along the fault segments is estimated as 1.21, 2.65 and 1.084 mm/y respectively. Based on fault parameter, and abnormal GLA, SL and Ks analysis, and slip rate, a new E‒W oriented active fault structure have been inferred, which passes through the Beldandi, Bilsan, Bachua, Nandgaon, Dhagadhi Surat Nagar, and Bhagwanpur locations. The combined results of the present investigation can be used for evaluation of seismic hazard in the central section of Indo‒Nepal Himalayan front.

Evaluation of tectonic activity using morphometric indices: case study of the Tatra Mts. (Western Carpathians, Poland)

The Tatra Mountains (Tatra Mts.) are the highest and most glacially reshaped mountain massif in the Carpathians. Previous studies suggested the tectonic uplift of this massif along the large sub-Tatric fault during Quaternary. The main goal of this paper is to characterise the tectonic activity in the Tatra Mts. using 6 geomorphic indices for 78 drainage basins: the stream-gradient index (SL), asymmetry factor (Af), basin shape ratio (Bs), hypsometric integral (Hi), valley floor width–valley height ratio (Vf), as well as mountain-front sinuosity (Smf). These parameters were combined in order to obtain the relative tectonic activity index (Iat) using GIS. The average of the six computed geomorphic indices was used to evaluate the distribution of relative tectonic activity in the study area. According to Iat values, four classes of different tectonic activity can be distinguished in the Tatra Mts.: class 1 of very high tectonic activity (0.7% of Tatra Mts.); class 2 of high activity (24.3%); class 3 of moderate activity (68.4%); and class 4 of low activity (6.6%). Our study confirmed previous suggestions about unequal uplift of different parts of the massif. Iat values show high tectonic activity along the Sub-Tatric fault, as well as in the northern part of the Belianskie Tatra. Distribution of Vf and Hi values correlate with extend of glaciers during Last Glacial Maximum. It seems that values of some geomorphic indices, such as Vf and HI, are strongly associated with glacial reshaping of the Tatra Mts. during the Pleistocene.

DEM-derived geomorphic indices for assessment of tectonic activity at the Dara anticlinal oil structure within the Zagros fold-thrust belt, southwestern Iran

The Dara anticline is one of the anticlinal oil structures in the Zagros fold-and-thrust belt that were formed in the Dezful Embayment west of the Kazerun fault zone. Determination of the tectonically active parts of this structure is important for structural analysis and oil exploration. Consequently, we have used Arc GIS software to analyze active tectonics indexes including the following: hypsometric integral and hypsometric curve (Hi, Hc); elongation ratio (Bs, Re); drainage asymmetry factor (AF); valley floor width to height ratio (Vf); stream gradient index (SL); and swath profile with remote sensing applied to a digital elevation model (DEM). These methods indicate the amount of active longitudinal growth of the Dara anticline. The tectonic activity analyses show that both the northwest and southeast noses of the Dara anticline are more active than the middle parts and that the SE nose is more active than NW nose.

Analysing riverbed morphology as a response to changes of geological and neotectonic conditions: A case study of the oľšava river

Abstract The morphological examination of the Slovak Oľšava River channel and valley parameters is based on observation of changes in the troughs’ longitudinal profile. While the relationship between valley and channel parameters has previously been researched, establishment of the diverse conditions in trough formation enables better understanding of the basin/riverbed relationship. Our research is based on field measurements of representative sections of nine segments defined by changes in the longitudinal profile. The field measurements were performed in autumn months during a low water period to ensure the best conditions for repeated measurements. Significantly, as much as 75% asymmetry of the measured flow encourages the assumption of strong tectonic influence on the riverbed formation. While the difference between the assumed continuous changes of measured parameters and the actual measured or evaluated parameters remains a matter of interpretation, the detected anomalies enable interpretation of the parameters’ relationships. The river bed and the valley morphological parameters were evaluated on the model of The Olšava River basin which drains the eastern part of the Košická kotlina Basin (the Toryská pahorkatina Upland). The location of the basin at the foot of the Slanské vrchy Mts. is an important factor in the formation of the river network asymmetries. Both the Neogene contact between the Slanské vrchy Hills neo-volcanites and the Toryská pahorkatina Upland and the neo-tectonics influenced the change in morphological parameters in the valley’s longitudinal and transverse profile and the Oľšava river bed. Our terrain works comprised length and width measurements of the bars, their positions in the river bed, the width and depth of the channel and the type of section riffle. Available maps enabled calculation of the following; ratio of valley height to width, average gradient of the section, stream gradient index, average channel segment slope, the degree of sinuosity and the highest observed correlation between slope, river segment type (0.9576) and the width and type river reach (−0.9089). High correlation coefficient values were recorded for the valley height and width ratio, the type of river section, the water area and the total river bed width and area.

Active tectonic deformation of the Shillong plateau, India: Inferences from river profiles and stream-gradients

The Shillong plateau in northeast India constitutes an actively deforming anticlinal basement uplift in the foreland of the Himalayas in the north and the Indo-Burman ranges in the east. The study aims to document zones of active crustal deformation in the Shillong plateau through the interpretation of the geometry and the quantitative analysis of stream profiles derived from 30-m SRTM DEM.Longitudinal profiles of the streams draining the plateau exhibit conspicuous convex upward reaches, mainly to the upstream of faults and in areas of deep river incision. Analysis of river profiles using Hack’s stream-gradient index (SL-index) reveals perturbations in profiles and steep channel-gradients in the middle reaches of the streams.Spatial distribution of the SL-index brings out extensive zones of anomalously high stream-gradients along the monoclinal flexure at the southern margin of the plateau adjacent to the Dauki fault and along the northern margin, where multiple en echelon faults define step-like topography. In the western part of the plateau, spatial association of zones of high stream-gradients with well-defined fault-scarps is suggestive of active crustal deformation by differential vertical movement along faults.The observed spatial distribution of anomalously high stream-gradients is uncorrelated with the lithological variations and hence, perturbations in river profiles and abrupt changes in stream-gradients are suggestive of differential tectonic uplift of the plateau. The study suggests that the rate of active tectonic deformation in the plateau decreases from the east to the west.

Drainage Pattern and its Bearing on Relative Active Tectonics of a Region: A Study in the Son Valley, Central India

ABSTRACT The paper emphasis the participation of different geomorphic parameters related to various characteristics of drainage in evaluation of active tectonics of an area. For the purpose, the morphotectonic evaluations of the Son valley, central India have been carried by involving various drainage related geomorphic indices viz., stream-gradient index (SL), hypsometric integral (HI), drainage basin asymmetry (AF), valley floor height and width ratio (Vf), transverse topographic symmetry factor (T), mountain front sinuosity (Smf), drainage basin shape (BS) and sinuosity index (SI) and relative rock strength (RRS) for classification of relative index of active tectonics (RIAT) in geographic information systems (GIS) environment to understand the role of active tectonics in geomorphologic evolution of the studied region. The established RIAT classes through field validations categorize the valley into four zones such as class 1- low activity ( RIAT < 2.7); class 2-moderate activity ( RIAT =2.7 < 2.99); class 3- high activity (RIAT=2.99 < 3.29); and class 4-very high activity (RIAT>3.29). The sub-dendritic, rectilinear and parallel linear drainage styles in RIAT classified basin reveal the traverse of a network of seventeen faults in association with two major faults namely Son-Narmada-North Fault (SNNF) and Son-Narmada South Fault (SNSF) in variable associations of rocks and multiple types of structural elements present in the Son valley. The signature of vertical upliftments may indicate the instability tectonic activities along the identified network of faults associated with SNNF and SNSF. Hence, the study suggests variable tectonically activeness of area in the Son valley.

Assessment of the Tectonic Activity in Northwestern Part of the Zagros Mountains, Northeastern Iraq by Using Geomorphic Indices

The Tectonic Activity of regions with active tectonics can be assessed by using of the geomorphic indices. Six Geomorphic indices including stream-gradient index (SL), drainage basin asymmetry (Af), drainage basin shape (Bs), hypsometric integral (Hi), valley floor width-valley height ratio (Vf), and mountain-front sinuosity (Smf) were calculated using GIS technique in Kifri Chai Basin; northeast Iraq, which belongs to the Western Zagros Mountain. The basin was divided into eighteen sub-basins depending on the 4th, 5th and 6th stream orders of the drainage within Kirfi Basin. It was found that the SL, Af, Bs, Hi, Vf, and Smf (J) values are uniform and exhibit almost the same classes. However, few exceptions occur, especially in Bs values, but the exceptional values do not influence significantly on the acquired results, in each of the eighteen sub-basin. From these indices the relative active tectonics index value (Iat) was determined. The results of average Iat values (2.35) showed that the tectonic activity in the whole basin is Moderate. Moreover, an attempt was carried out to compare the regional Neotectonic activity with the relative tectonic activity in the basin. The results showed that there is a positive relation between the two comparatives; especially the subsidence amount and scored relative tectonic activity.

Hierarchical anomalies in drainage network: a case study from Western Ghats, South India

The Chalakudy river, a seventh order tropical drainage system emerging from the Western Ghats is flowing through the Southern Granulite Terrain of Peninsular India. Anomalies in the hierarchical organization of drainage networks reflect the effects of anthropogenic interferences and structural controls in the development of a drainage basin. The anomalies in the drainage composition are determined from bifurcation index, hierarchical parameters and stream gradient index. Computation of drainage indices is carried out with the aid of vectorized data derived from Survey of India (SOI) open series topo maps and Shuttle Radar Topographic Mission (SRTM) data (3Arc resolution) using ArcGIS 10.4 software. Here we discuss the quantitative methodology to determine the hierarchical anomaly index, hierarchical anomaly density and hierarchical anomaly number of drainage basin from geospatial data with an attempt to infer the degree of geomorphic evolution of the sub-basins from the analysis. The sub-basins are in their mature to the late mature stages of geomorphic evolution. It is observed that the tectonically induced diffusive process and anthropogenic interferences in the drainage basin altered the hierarchical organization of drainage network of Chalakudy river basin.

Geomorphic Indices of Tectonic Activity Through the Analysis of the Drainage Systems in Pera Magroon Anticline, Northeastern Iraq

The study area (Pera Magroon) is located within Kurdistan Region, Sulaimaniyah Governorate, north and northwest of Sulaimaniyah city northeastern Iraq. Arc GIS, hydro tool is used to extract the drainage network in the area under study by using digital elevation models (DEM). The study area is covered by dendritic and parallel drainage patterns and divided into twenty sub-basins. Three geomorphic indices, Mountain-front sinuosity (Smf), Stream-gradient index (SL) and Valley floor width-valley height ratio (Vƒ) were calculated for sub- basins. Through averaging these three indices, we obtained index of active tectonics (IAT). The values of the index were divided into classes to define the degree of active tectonics. Therefore, relative tectonic activity is calculated and their values are classified and analyzed in three groups. The sub-basins were identified as very high, high and moderate levels..