Hypsometric Integral Values Research Articles

Segmentation of the active Liumugao Fault, NE Tibetan Plateau as revealed by DEM-derived geomorphic indices

As the secondary fault of the Niushoushan-Luoshan Fault Zone, the Liumugao Fault records the northeastward expansion of the Tibetan Plateau. Based on WorldDEM data, 11 rivers (R1-R11) that flow across the Liumugao Fault and their drainage basins were extracted using ArcGIS technology and a MATLAB script. The longitudinal profiles, Hack profiles, and stream length-gradient (SL) indexes of these rivers, as well as the hypsometric integral (HI) of their drainage basins, were extracted and calculated and combined with field observations to quantitatively analyze the activity of Liumugao Fault. The results show that: (1) the longitudinal profiles of the 11 rivers are steep, the Hack profiles of most rivers drop sharply at the main fault, and the average HI value of the drainage basins is ∼0.4. These phenomena indicate that the current activity of the fault is strong. (2) The average HI values of the drainage basins in the northern, middle, and southern segments of Liumugao Fault are 0.32, 0.37 and 0.45, respectively. Accordingly, the average normalized stream-gradient (SL/K) values of the three segments are 3.72, 4.64 and 7.16, respectively. These data show that the activity of the Liumugao Fault gradually increases from north to south.

Dynamic river basins and hypsometric analyses: implications to land management and prioritization in Bohol, Central Philippines

ABSTRACT The study presented a method of characterizing landform dynamics that integrates a divide stability metric and hypsometric analysis. Chi (χ) - a proxy for steady-state river channel elevation - indicated a drainage divide stability. Simultaneously, the hypsometric analysis provided information on a basin's geologic development stage and erosion proneness. The study used a 30 m SRTM digital elevation data, the DivideTool/TopoToolbox of MATLAB, and the SWAT model. The tool computed χ values following the stream network, enabled the selection of divide sections, extracted channel head's χ values, determined divide stability by predicting migration direction for unstable divides, and produced histograms of χ values for each divide section. Equal χ values at the channel heads of opposing river networks indicated a stable divide. In contrast, a difference in χ values suggested an unstable divide and a potential to migrate from low χ values towards the divide's high χ values side. The study proposed the mean χ difference (χmd ) metric to indicate the degree of divide mobility. Meanwhile, the SWAT model defined the basins and subbasins and set the hypsometric analysis parameters. Each subbasin's hypsometric integral (HI) was used to create a continuous surface of HI values. The combination of χmd and HI analysis revealed nine subbasins with highly mobile divides and high erosional areas, identifying them as high-priority conservation zones. River basin characterization can utilize the new approach to target areas for location-specific land and water conservation measures and other developmental goals.

Geospatial assessment of active tectonics using SRTM DEM-based morphometric approach for Meghalaya, India

Meghalaya, situated over the Shillong Plateau in the northeastern region of India, is considered a seismo-tectonically active region because of the Indian-Eurasian convergence and rising since the Cenozoic era. The present study aims to identify active deformation zones due to tectonic activity following a morphometric approach. Based on DEM data and GIS techniques, morphometry parameters along with geomorphic indices are obtained which allows the analysis of geomorphic processes responsible for the region’s landscape evolution, and indices of relative active tectonics (IRAT) are calculated by combining them. High drainage density, larger ruggedness number, intermediate to high hypsometric integral values with S/convex-type hypsometric curve, lower valley floor width-to-height ratio and stream sinuosity index values suggesting the region is tectonically active and according to IRAT, the Khasi and Jaintia Hills region (the central and eastern part) of the Meghalaya possesses relatively higher tectonic levels. The variation of tectonic activity is not uniform in the same structural feature and is found to be lower in the western portion and higher towards the east along the same Dauki Fault.

The Hypsometric Integral Based on Digital Elevation Model for the Area West of Lvliang Mountains in Loess Plateau, Shanxi, China

A hypsometric integral (HI) is a topographical index with important geomorphological meaning. It can both describe the development state of the watershed and reflect the strength of activity in the geological structure. Based on this index, the integral curve method was used to analyze the HI characteristics of watersheds in the region west of the Lvliang Mountains on the Loess Plateau of Shanxi Province, China, in combination with 30-m resolution Shuttle Radar Topography Mission data. In order to accurately characterize erosion development within the watershed, the HI characteristics of each topographic feature object in the watershed were comprehensively analyzed. The results of HI scale effects show that HI was not strongly dependent on the spatial resolution of Digital Elevation Model (DEM) data, but had some scale dependence on the stable area of the watershed. The spatial distribution of the HI shows that the HI values of the watersheds in the southern loess residual tableland were the largest, and the degree of erosion was the weakest; the HI values of the watersheds in the north-central part of the loess hilly-gully region were relatively small, and the degree of erosion was stronger. This result is consistent with the results of the spatial distribution of sediment yield in literatures. The reasons for the spatial distribution of the HI were analyzed in terms of geological formations and climatic environments. The results show that for the study area, tectonic activity, formation lithology, rainfall, and agrotype were not the main factors affecting the HI values. The structure of the paleotopography and erosion cutting due to the uplift of the Lvliang Mountains and later water erosion controlled the spatial distribution state of HI. Thus, for the study area, the HI value cannot reflect the strength of tectonic activity. The combination of topographic feature object method and the HI index further quantified the erosion development state of the watershed.

Morphometric characterization and erosion assessment of gullies in the lateritic badlands of Eastern India using ALOS AW3D30 DEM and topographic indices

The present geomorphic study analyzes the morphometric anomalies of the lateritic badlands (West Bengal, India) to understand the erosion intensity, triggering factors and landscape evolution using the ALOS AW3D30 DEM and quantitative techniques of various hydro-geomorphic processes (viz., basin morphometry, rainfall-runoff simulation, geomorphic threshold, erosion indices, sediment yield, SPI, and STI etc.). The GIS-based analysis reflects that there is the requitement of minimum drainage area (i.e. 55.71–349.01 m2) to maintain one metre of gully channel in the basins which have the network density of 2.86–13.76 km km−2. The critical slope (i.e. geomorphic threshold) of badland terrain varies from 0.0222 to 0.0407 metre metre−1, having dominance of overland flow erosion to initiate gully heads. The basin-wise SCS-CN and USLE coupling estimates that within the daily rainfall range of 11.41–66.41 mm day−1, the potential sediment yield of gully basins varies from 2.15 to 9.10 t ha−1. The S L index (i.e. 0.81–47.32 m) diagram reflects the beats of gully energy profile due to stream erosion enhancement, slope steepness, resistance of underlying lithologies and active tectonics. Hypsometric integral values of the gully basins, ranging from 0.4 to 0.6, emphasize a low entropy-based fluvial system and development of mature-youthful landform stage. The evolutionary stages of badlands are explained here by the connectivity model and hillslope – gully – river coupling system, showing a quasi-equilibrium to complex stage of landscape development at present.

Hypsometric Analysis of Watershed using Geographical Information System

Hypsometry of drainage basins (area-elevation analysis) has generally been used to reveal the stages of geomorphic development (stabilized, mature and young). In the present study, Kanoli river watershed located in Nashik district of Maharashtra was considered as the study area. The watershed was delineated into seven sub-watersheds and hypsometric analysis was carried out for all of them using the digital contour map, which was generated using Arc/Info GIS. In analysis, a curve is derived by plotting the relative heights (h/H) and relative areas (a/A); the obtained curve is called as hypsometric curve. The area under the Hypsometric curve is the Hypsometric Integral (HI). The hypsometric integral values for all of the sub-watersheds of Kanoli river ranges between 0.45 and 0.88. It was observed from HI that the sub-watersheds WS2, WS4, WS6 are in the mature stage and moving toward the deteriorating stage. The sub-watershed WS3 yielded higher hypsometric integral value, explaining its late youthful stage which calls for suitable measures of soil and water conservation. Further, sub-watersheds WS1, WS5 and WS7 have got very high value of hypsometric integral which takes them to young stage i.e. very susceptible to erosion. Therefore, these sub-watersheds are more prone to subsequent erosion activities and needs immediately appropriate soil and water conservation measures

Quantifying the Geomorphology of the Drainage Basins Along the Greater Khingan Mountains in NE China

Drainage basins are fundamental elements of the earth’s surface, and quantifying their geomorphic features is essential to understand the interaction between tectonics, climatic, and surface processes. In this study, 40 basins of the Greater Khingan Mountains were selected for hypsometric analysis using a 90-m Shuttle Radar Topography Mission digital elevation model. The hypsometric integral values range from 0.13 to 0.44, with an average value of 0.30, and most hypsometric curves exhibit remarkable downward concave shapes. This feature indicates that most drainage basins and the landscape of the Greater Khingan Mountains are approaching the old-age development stage, consistent with the present moderately stable tectonic activity. The spatial distribution of the χ values is characterized by unambiguously higher values on the western flank than those on the eastern flank in the middle and southern segments of the Greater Khingan Mountains. We interpret this as an indicator of the disequilibrium across the main divide. The interpolation of the erosion rates and channel steepness for the catchments on both sides of the Greater Khingan Mountains revealed westward divide migration, which is consistent with the lower χ values, a higher slope, and local relief observed along the eastern flanks. Considering the long-term tectonic evolution pattern between the Greater Khingan Mountains and Songliao Basin, the landscape decay and slow westward divide migration were mostly driven by the inherited Cenozoic tectonics and precipitation gradient across East Asia.

Active Tectonics of Gülbahçe Fault Zone (GBFZ) by Using Geomorphic Indices, İzmir Province, Western Anatolia, Turkey

The Gülbahçe Fault Zone is a dextral strike-slip fault that extends for ~24 km on land and ~46 km under the sea, which consists of the significant southernmost active segments of İzmir Balıkesir Transfer Zone. In this study, the active tectonic behaviour of the Gulbahçe Fault Zone was evaluated by using of morphometric analysis of geomorphic indices. 30 sub-basins identified using ArcGIS ®10.5 (ESRI). All sub-basins were calculated by using mountain-front sinuosity (Smf), valley-floor width to valley height ratio (Vf), basin asymmetry factor (Af), basin shape indice (Bs), drainage density (Dd), and hypsometric integral (Hi) values. The obtained mean results of values are to define each sub-basin's relative tectonic activity (Iat). The Smf, Vf, Af, Bs, Dd, and Hi values range from 1.05 to 1.33; from 0.21 to 4.09; from 25 to 77; from 1.03 and 3.06; from 0.28 to 0.67, respectively. All the results were gathered under three classes, which sign high tectonics activity (Class 1), moderately active tectonic (Class 2), and low tectonics activity (Class 3). The results show that relative active tectonics indice value (Iat) was obtained between 1.33 and 2.33, indicating very high to moderately tectonic activity.

Estimation of flood influencing characteristics of watershed and their impact on flooding in data-scarce region

ABSTRACT The research is focused on the integrated use of satellite remote sensing, Geographic Information System (GIS), and extensive field observation techniques for a better understanding of the impacts of watershed characteristics on hydrological processes and floods. It aims to create a methodology for assessing flood hazards and risk on a regional and local scale so that protective measures can be designed. Floods have occurred in the study area for many years, causing serious damage to infrastructure and civic structures. The present study evaluates the linear, aerial and relief morphometric parameters using the Cartosat-1 digital elevation model (30 metres) along with the curve number for assessing the flood influencing characteristics of the Vishwamitri River’s sub-watersheds. The study prioritizes five sub-watersheds as high, medium, and low based on their flood influencing characteristics and compound value, as a result, needs the highest priority for flood mitigation measures. The sub-watersheds I and IV of Vishwamitri watershed have been categorized into high priority, sub-watersheds II and V into moderate priority, and sub-watershed III into low priority. The geologic stage of development and erosion proneness of the watershed is quantified by hypsometric integral bearing value as 0.04, indicating the landscape to be in monadnock phase in landscape evolution indicative of a marked old stage in the basin’s evolution. Moreover, the ability of the rain-on-grid model at the watershed scale to simulate flood events and predict flood-prone areas, considering multiple rain gauge data, which will facilitate more accurate flood inundation where ground-based observational data are unavailable is shown.

Assessment of soil erosion, flood risk and groundwater potential of Dhanari watershed using remote sensing and geographic information system, district Uttarkashi, Uttarakhand, India

Quantitative morphometric analysis of Dhanari watershed has been done using remote sensing and Geographical Information System (GIS). The impact of climate, lithology, tectonics, structural antecedents, vegetation cover and land use on hydrological processes is assessed by quantifying geomorphic parameters. The Dhanari River (a tributary of the Bhagirathi River) and its tributaries Dhanpati Gad and Kali Gad forms Dhanari watershed covering 91.8 Km2 area. Several geomorphic aspects viz. linear, areal, relief were computed to comprehend potentials of soil erosion, groundwater, flood vulnerability and the geomorphic response of watershed. LISS-III image is used to generate the Land Use and Land Cover (LULC) map and assess the watershed dynamics. Values of computed hypsometric integral and morphometric parameters viz. drainage density (D_{{text{d}}}), stream frequency (F_{{text{s}}}), stream length ratio (L_{{{text{ur}}}}), bifurcation ratio (R_{{text{b}}}), rho coefficient (ρ), drainage texture (D_{{text{t}}}), circularity ratio (R_{{text{c}}}), relief ratio (R_{{{text{hl}}}}), elongation ratio (R_{{text{e}}}), form factor (F_{{text{f}}}), basin shape (B_{{text{s}}}), drainage intensity (D_{{text{i}}}), compactness coefficient (C_{{text{c}}}) and infiltration number (I_{{text{f}}}) have shown a moderate and steady erosion rate, with low groundwater potential and low to moderate flood vulnerability in the watershed. Hypsometry presents a dependable geomorphic parameter to understand the erosion and geomorphic response of a watershed to hydrological processes. Hypsometric integral value (0.51) of Dhanari watershed suggests a mature topography with steady erosion in the watershed.

Novel Technique to Investigate Glacio-fluvial Hypsometry in Hunza Using Local Indicator of Spatial Autocorrelation (LISA)

Hypsometric Integral (HI) displays the effect of active tectonics and sensitivity on geomorphic structures. In this study we calculated HI values for Hunza valley to investigate neotectonics, development of topographic structures and process of erosion using SRTM DEM 90m. ArcGIS and MATLAB is used to generate HI and hypsometric curve (HC). We generated HI and HC values by using D8 algorithm in MATLAB to extract drainage basins for 5 and 6 Strahler orders. HI and HC values show the stages of erosion for instance high values of HI and convex HC displays young and tectonically active stage. We used different grid sizes in ArcGIS to calculate maximum, mean and minimum elevation utilizing different statistical techniques. We used Local Indicator of Spatial Autocorrelation (LISA) instead of Global Moran Index to determine the extent of distribution of clustered, dispersed and randomized HI values. This technique indicates high positive z score for auto correlated data. Regions with high HI value indicate relative uplift, undissected and young structures while low HI values indicate sediment accumulation and shallow earthquakes.

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.

Geomorphic expression of shear zones in Southern Brazilian and Uruguayan Shields

Earth's surface is a result of complex tectonic and erosional processes shaping landscapes and producing transient signs of different evolutionary stages. These transient signs are formed by a gradual adjustment of rivers to an equilibrium stage through channel incision and uplift. Processes have different magnitudes according to lithological contrasts and base-level changes that result in distinct disequilibrium phases of bedrock rivers. This integrated study of geomorphic indices in bedrock rivers of the southernmost Brazilian and Uruguayan Shields is developed to identify key signs of transience associated with surface processes and compare with contrasting drainage basin results. The study area is composed of igneous-metamorphic rocks of Precambrian age of the Dom Feliciano Belt amalgamated during the Proterozoic-Phanerozoic boundary in the Brasiliano Orogeny. Digital elevation models (DEM) are used to extract hypsometric indices, χ-plots for each basin, and an interpolated Ksn map through interactive MATLAB tools emphasizing erosional stages and uplifted regions. Hypsometric integral values varying from 0.20 to 0.45 and a mean concavity of 0.5 show an overall eroded landscape, however, knickzones, positive χ-curves and Ksn anomalies of up until 45 reveal transient landscape signs in the area. Combined hypsometric, χ-plots and Ksn anomalies reveal distinctive patterns of erosion and uplift components with knickpoints aligned to structural signatures of lineaments. In the Sul-rio-grandense Shield (SRGS), these patterns point to a rugged and reworked relief controlled by shear zones, whereas the Uruguayan Shield (UYS) shows a denudated and more stable topography. Major tectonic events are well constrained in the Dom Feliciano Belt, but the timing and driving forces of the geomorphological features remains difficult to estimate because of the long geological history involved and intraplate context.

A Study of Active Chaman Fault System (CFS) using SRTM DEM

Chaman fault is a seismically active fault running over 850km in western region of Pakistan and Afghanistan. It is a major geological structure between Indian and Eurasian plates. Chaman fault is a strike slip fault which is slipping nearly at the rate of 10mm per year. This research includes the evaluation of lithological processes and neotectonics activity using Hypsometric Integral (HI). We calculated values of hypsometric integral using SRTM DEM with 90m spatial resolution in active region of Chaman Fault (CF) and in its locality. We analyzed different mean, minimum and maximum elevations using regular square grids and measured the degree of spatial distribution of HI using Local Indices (LI) of Spatial Autocorrelation (LISA). LISA provides auto correlation for the cluster analysis of hotspots and cold spots of HI values to discriminate uplifted and eroded regions.

HYPSOMETRIC ANALYSIS OF AL-ADHAIM BASIN USING A NEW GIS- TECHNIQUE

Al-Adhaim dam basin is extended across the boundaries of Salahuddin, Kirkuk, and Sulaymaniyah provinces in the northern part of Iraq, covering an area of 11831 km2. The area is covered mainly in most upperparts by sedimentary rocks of the lower Eocene to Pliocene ages. The lower parts are occupied by sheet runoff deposits from the Quaternary age. The objectives of the current study are to carry out detailed measurements of hypsometric parameters to evaluate the degree of erosion conditions and to show the essential factors controlling the development of geomorphic stages in different parts of the basin. The analysis was carried out based on ASTER GDEM data using ArcGIS v10.6 hydrology toolbox and the morphometric toolbox and dividing the basin into fifteen sub-basins. The results show that the Al-Adhaim basin passes in the monadnock phase with a hypsometric integral of 19.02% and a highly concaved hypsometric curve. The sub-basins are classified into two groups of geomorphic stages, i.e., mature stage and Monadnock stage with hypsometric integral values between 18.4% and 34.6%. The results reveal the basin was controlled mainly by slopes, lineaments, Tertiary outcrops, Quaternary deposits, and hydrological soil groups B and D.

Temporary and net sinks of atmospheric CO<sub>2</sub> due to chemical weathering in subtropical catchment with mixing carbonate and silicate lithology

Abstract. The study provided the major ion chemistry, chemical weathering rates and temporary and net CO2 sinks in the Bei Jiang, which was characterized as a hyperactive region with high chemical weathering rates, carbonate and silicate mixing lithology, and abundant sulfuric acid chemical weathering agent of acid deposition and acid mining drainage (AMD) origins. The total chemical weathering rate of 85.46 t km−2 a−1 was comparable to that of other rivers in the hyperactive zones between the latitudes 0 and 30∘. A carbonate weathering rate of 61.15 t km−2 a−1 contributed to about 70 % of the total. The lithology, runoff, and geomorphology had a significant influence on the chemical weathering rate. The proportion of carbonate outcrops had a significant positive correlation with the chemical weathering rate. Due to the interaction between dilution and compensation effect, a significant positive linear relationship was detected between runoff and total carbonate and silicate weathering rates. The geomorphology factors such as catchment area, average slope, and hypsometric integral value (HI) had nonlinear correlation with chemical weathering rate and showed significant scale effect, which revealed the complexity in chemical weathering processes. Dissolved inorganic carbon (DIC) apportionment showed that CCW (carbonate weathering by CO2) was the dominant origin of DIC (35 %–87 %). SCW (carbonate weathering by H2SO4) (3 %–15 %) and CSW (silicate weathering by CO2) (7 %–59 %) were non-negligible processes. The temporary CO2 sink was 823.41×103 mol km−2 a−1. Compared with the temporary sink, the net sink of CO2 for the Bei Jiang was approximately 23.18×103 mol km−2 a−1 of CO2 and was about 2.82 % of the “temporary” CO2 sink. Human activities (sulfur acid deposition and AMD) dramatically decreased the CO2 net sink, even making chemical weathering a CO2 source to the atmosphere.

Application of morphometric techniques for the delimitation of Borborema Highlands, northeast of Brazil, eastern escarpment from drainage knick-points

This article seeks to contribute to the understanding of the dynamics and evolution of landforms, on a regional scale, from the application of morphometric indexes and structural analyzes, in the eastern portion of the Borborema Highlands, Northeast Brazil. The aim of this analysis is to minimize the subjectivities of the classifications and morphological hierarchies in the region in question. We sought to relate the morphology of the eastern sector of Borborema Highlands and the drainages that flow into the Atlantic, thus obtaining a morphometric indicator that would establish, in a quantitative fashion, how this relationship presents itself in the geomorphological landscape, in addition to proposing numerical and morphological thresholds that permitted the delimitation of the Highlands eastern escarpment. For that, the SL/K index was applied, based on HACK (1973) original propositions, subsequently adapted by Seeber and Gornitz (1983), in order to identify sectors of major regional gradient breaks. The Hypsometric Integral values were also obtained in search for correlations between drainage erosion capacity and regional flexural and tectonic influences. Distance measurements between anomalous sectors and base levels on the coast were added. The indexes were applied to the main watersheds that drain the eastern escarpment of the Borborema Highlands: Paraíba (PBW), Goiana (GOW), Capibaribe (CAW), Ipojuca (IPW), Sirinhaém (SIW), Una (UNW) and Mundaú (MUW). It was observed that the sectors identified as regional breaks on relief levels are found at different elevations, varying between 150m and 275m, instead of 200m as traditionally designated by regional literature. It was also observed that on the Transversal Zone, between Patos and Pernambuco lineaments, only one major regional gradient break occurs, whereas to the south of the Pernambuco Shear Zone more than one regional breaks were found, indicating a predominantly flexural influence in the first context and a more brittle in the second. As for the Hypsometric Integral, it was observed that the relationship commonly made between its values and evolutionary stages in the Davisian sense was not found.

Original

In the present study, an attempt is made to study the areal and relief aspects of morphometry of Suktel River, a tributary of Tel River and its subbasins that flows through Bolangir District of Odisha. The study is done using SRTM dem and GIS. Freely available SRTM Dem (30-meter resolution) has been processed to delineate the streams and the watershed. Its various linear, aerial and relief parameters have been delineated using Arc GIS 10.3. The results show that Suktel basin is a sixth-order basin having a dendritic drainage pattern. It has an elongated shape with coarse drainage texture. The highly concave upward hypsometric curve and low integral values ranging between 0.12 and 0.19 for the study basin and its subbasins imply that the basin is in the monadnock phase of basin development characterised by flat terrain with very low relief.

GIS-based sub-watershed prioritization through morphometric analysis in the outer Himalayan region of India

The study indicates the viability of geographic information system and remote sensing data for the analysis as well as estimation of the stage and the rate of erosional processes in a Himalayan watershed for improved planning and management. The Gaj watershed lies in the outer Himalayan region of Himachal Pradesh, India, which has been characterized in to nine sub-watersheds for studying the geomorphological evolution of each separately for comparative assessment irrespective of any scale issue. The method involves the use of 30 m Cartosat (digital elevation model) for operative and time-saving data extraction of morphometric and hypsometric parameters. The estimated hypsometric integral values and the shape of the hypsometric curves reveal varying degree of erosional stages of the sub-watersheds demanding attention over the denudation activities. The results have helped in the qualitative discussions and prioritizing the sub-watershed for sustainable soil–water conservation and management, which can be useful for controlling the erosional activities at right locations in the study area.

Geomorphic expressions of collisional tectonics in the Qilian Shan, north eastern Tibetan Plateau

The Qilian Shan, north eastern Tibetan Plateau, is an area of active deformation caused by convergence in the India-Eurasia collision zone. Geomorphic indices capture the landscape response to competition between tectonics and climate, reflecting the spatial distribution of erosion. We use geomorphic indices (hypsometric integral (HI), normalised channel steepness (ksn), elevation-relief ratio (ZR) and surface roughness (SR)) to identify areas of active deformation and erosion, highlight landscape variations and we interpret the results for potential tectonic and climatic drivers. High HI (> 0.15), ksn (> 100) and low ZR (< 2) occur in the hanging wall of thrust faults, consistent with active uplift of these structures. Relatively high HI (> 0.15) and ksn (> 100) values in the eastern region are attributed to thrust parallel rivers in this region excavating wide valleys between the faults. The east-west precipitation variation across the Qilian Shan (>500 mm/yr to <100 mm/yr) is not a first order control on the regional landscape. There is an abrupt northwards transition from low to high HI, ksn and SR and high to low ZR partially coincident with the left-lateral Haiyuan Fault. We suggest that this transition is due to a difference in deep structure. A south-to-north transition from creeping to locked behaviour on an underlying detachment thrust has previously been suggested to occur along the intersection of this thrust detachment with the overlying Haiyuan Fault, providing a potential explanation for the location of the geomorphic change. Our results show these geomorphic indices to be sensitive to the underlying tectonic structure of the area. These methods could be applied to other fold-and-thrust belts and tectonic settings, to help understand the underlying structure, and the processes responsible for deformation.