Basin Shape Index Research Articles

Index of Active Tectonic Assessment: Quantitative-based Geomorphometric and Morphotectonic Analysis at Way Belu Drainage Basin, Lampung Province, Indonesia

The occurrence of subduction zones caused by the collision between the Eurasian-Western Indonesia Plate due to an increase tectonic, volcanic and magmatic activities along Sumatra Island. This study covers the area of Way Belu Drainage Basin, located near Bandar Lampung City, Lampung Province, southern part of Sumatra, Indonesia. The area composes of a complex geological structure as the result of tectonic activities. In this study, geomorphic indices assessment such as morphometric and morphotectonic quantitative analysis are undertaken to identify the Index of Active Tectonics (IAT). The morphometric analysis uses Drainage density (Dd) and Ratio of bifurcation (Rb). The value of Dd respectively from 1.45 to 4.05, Rb from 2 to 10. While the morphotectonic analysis uses basin shape index (Bs), valley floor width-valley height ratio (Vf), and asymmetry factor (AF). The value of Bs from 1.27 to 6.25, Vf from 0.16 to 3.30, and AF from 22.73 to 83.77 in ranges which is derived average IAT value is 2.20. It may considered that at the Way Belu Drainage Basin has moderate to high tectonic activity. From the joint measurement results on the fracture zone express that the main pattern of faults has trend NWW-SSE, NE-SW, NNE-SSW, NW-SE, and W-E directions. Furthermore, based on the combination of the quantitative geomorphology indices assessment which is supported by remote sensing and field assessment shows that those features closely related to the Semangko Fault System with the NNW-SSE fault trend parallel to its fault.

Water system characteristics of Karst river basins in South China and their driving mechanisms of hydrological drought

It is common knowledge that drought is considered one of the most damaging natural disasters in terms of economic costs, societal problems, and ecological impacts. In this study, we selected 53 Karst drainage basins in South China as research areas and automatically extracted the characteristics of water system based on 30 m DEM data using GIS technology. The surface confluence and runoff process of atmospheric precipitation were simulated by BP neural network, and we analyzed space coupling of drainage characteristics and studied their driving mechanisms for hydrological drought. Results show that (1) basin shape index, river network density, and main channel’s longitudinal slope respond positively to atmospheric precipitation, while other drainage characteristics respond negatively. This shows that drainage characteristics’ response to atmospheric precipitation gradually decreases from input layer to output layer, which means that watershed confluence capability gradually weakens. (2) Driving of drainage characteristics to runoff process is positive in the first hidden layer with its driving effect order arranged from small to big as follows: river network density 0.9), with excellent model significance (Sig. = 0.0).

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.

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.

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.

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.

Tectonic geomorphology of the Kemalpaşa Basin and surrounding horsts, southwestern part of the Gediz Graben, Western Anatolia

The Kemalpaşa Basin is one of the Quaternary basins in Western Anatolia and represents the south-western branch of the Gediz Graben system in this extensional province. This basin has been formed under the NNE–SSW trending extensional tectonic regime. It is bounded by a major fault, the Kemalpaşa Fault, in the south and it is bounded by a number of downstepping faults, called as Spildağı Fault Zone, in the north. Both margin-bounding faults of the Kemalpaşa Basin are oblique-slip normal faults. In order to better understand the activities of these faults, we investigated the tectonic geomorphology of the Kemalpaşa Basin and interpreted the effect of tectonic activity on the geomorphological evolution using geomorphic markers such as drainage basin patterns, facet geometries and morphometric indices such as hypsometric curves and integral (HI), basin shape index (Bs), valley floor width-to-height ratio (Vf) and mountain front sinuosity (Smf). The morphometric analysis of 30 drainage basins in total and mountain fronts bounding the basin from both sides suggests a relatively high degree of tectonic activity. The mountain front sinuosity (Smf) generally varies from 1.1 to 1.3 in both sides of the basin suggesting the active fronts and facet slopes (12°–32°) suggest a relatively high degree of activity along the both sides of the Kemalpaşa Basin. Similarly, the valley floor width-to-height ratios (Vf) obtained from the both sides indicate low values varying from 0.043 to 0.92, which are typical values (<1) for tectonically active mountain fronts. The all values obtained are lower for the southern side. Therefore, we suggest that the tectonic activity of the Kemalpaşa Fault higher than the Spildağı Fault Zone. This difference that can be arised from the different uplift rates also reveals the typical asymmetric characteristics of the Kemalpaşa Basin. Additionally, the trapezoidal facets which have been observed on the southern side of the basin indicate that the Kemalpaşa Fault is evolutionally more active as compared to the Spildağı Fault Zone. The geomorphic indices indicate that the Quaternary landscape evolution of the Kemalpaşa Basin was governed by tectonic and erosional processes, and also the all results of morphometric analysis suggest a relatively high degree of tectonic activity along the faults bounding the Kemalpaşa Basin. Moreover, considering that active large normal faults with an average 15 km long can cause major earthquake, the earthquake hazard in the Kemalpaşa Basin should be investigated in detailed paleoseismological studies.

GIS-based evaluation of geomorphic response to tectonic activity in Makran Mountain Range, SE of Iran

This paper investigates the impact of active tectonics on the geomorphic processes and landscape evolution of Makran Mountain range at southeastern of Iran using spatial analysis of geomorphic indices. We documented how topography and morphology are influenced by active tectonic deformation. Quantitative analysis of the geomorphological response to active tectonics within the study area have been done using drainage basin asymmetry factor (Af), drainage basin shape index (Bs), drainage density index (Dd), hypsometric integral (Hi), mean axial slope of the channel (MASC), topographic roughness (STD), mountain-front sinuosity (Smf) and valley floor width-valley height ratio (Vf). The obtained results from these indices were combined to yield an index of active tectonics (Iat). The indicative values of this index are consistent with the landforms and geology of the study area. The morphometric data (quantitative analysis of geomorphic indices) provides evidence of relative variation in the tectonic activity of the study area and related landforms. The utilization of geomorphic parameters exhibits decrease in the geomorphic response of the landforms from north to south. Also, the Ghasr-e-Ghand fault, based on the front-based indices has an important role in uplift of the middle part of the study area. Based upon the results of this study we suggest a southward tectonic vergence for the Makran Mountain Range.

Appraisal of active tectonics in Hindu Kush: Insights from DEM derived geomorphic indices and drainage analysis

Landscapes in tectonically active Hindu Kush (NW Pakistan and NE Afghanistan) result from a complex integration of the effects of vertical and horizontal crustal block motions as well as erosion and deposition processes. Active tectonics in this region have greatly influenced the drainage system and geomorphic expressions. The study area is a junction of three important mountain ranges (Hindu Kush-Karakorum-Himalayas) and is thus an ideal natural laboratory to investigate the relative tectonic activity resulting from the India-Eurasia collision. We evaluate active tectonics using DEM derived drainage network and geomorphic indices hypsometric integral (HI), stream-length gradient (SL), fractal dimension (FD), basin asymmetry factor (AF), basin shape index (Bs), valley floor width to valley height ratio (Vf) and mountain front sinuosity (Smf).The results obtained from these indices were combined to yield an index of relative active tectonics (IRAT) using GIS. The average of the seven measured geomorphic indices was used to evaluate the distribution of relative tectonic activity in the study area. We defined four classes to define the degree of relative tectonic activity: class 1__very high (1.0 ≤ IRAT < 1.3); class 2__high (1.3 ≥ IRAT < 1.5); class 3—moderate (1.5 ≥ IRAT < 1.8); and class 4—low (1.8 ≥ IRAT). In view of the results, we conclude that this combined approach allows the identification of the highly deformed areas related to active tectonics. Landsat imagery and field observations also evidence the presence of active tectonics based on the deflected streams, deformed landforms, active mountain fronts and triangular facets. The indicative values of IRAT are consistent with the areas of known relative uplift rates, landforms and geology.

Geomorphometric attributes of the global system of rivers at 30-minute spatial resolution

In this paper we explore the geomorphometric characteristics and integrity of a 30′ (longitude×latitude) spatial resolution representation of the global system of potentially-flowing rivers. We quantify several geomorphometric attributes of digital, Simulated Topological Network (STN-30p) depicting potential flow pathways across the entire non-glacierized surface of the Earth. This data set was examined with respect to several metrics describing individual grid cells, river segments, and complete drainage systems. Nearly 60,000 grid cells constitute the global non-glacierized land mass. The cells are organized into more than 30,000 distinct river segments belonging to approximately 6200 drainage basins. STN-30p flow paths and drainage basins are classified as order one through six using the classification system of Strahler. STN-30p flow pathways depict rivers draining a global land area of 133.1×106km2. These pathways show a total length of 3.24×106km at 30′ spatial resolution. The relationships between STN-30p order and interior river segment numbers, accumulated sub-basin areas, and accumulated length within individual basins yield high correlation coefficients (average r2>0.96 for continents and globe). Mean values across individual continents and river orders for the bifurcation ratio (3.15 to 4.44), drainage area ratio (3.74 to 5.77), and basin length ratio (2.02 to 3.27) fall well within the ranges tabulated at finer spatial scales. A basin shape index, Sb=L/A0.5, defined as a function of potential mainstem length and drainage area, varies between 1.0 and 5.0 for basins >25,000km2 and shows a global mean of 2.12. The structure of STN-30p potential river systems is consistent with those of rivers analyzed at finer spatial scales as demonstrated by the numerical similarity of the several geomorphometric indices analyzed. However, for a particular basin, indices from STN-30p will be based on a condensed set of river orders relative to those derived at finer scales. A first order STN-30p river is roughly equivalent to an order five-to-six river derived from 1:62,500 scale maps. While 30′ spatial resolution was found to represent well the 522 basins with areas >25,000km2 that drain 82% of the land mass, it cannot be used with high confidence in characterizing the geomorphometry of the remaining smaller basins. For global climate and biogeochemical studies, a composite of the 30′ resolution and finer spatial resolutions appears to be necessary.