Hypsometric analysis of Kali River Basin, Karnataka, India, using geographic information system

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1 Geocarto International Vol. 26, No. 7, November 2011, Hypsometric analysis of Kali River Basin, Karnataka, India, using geographic information system Vipin Joseph Markose and K.S. Jayappa* Department of Marine Geology, Mangalore University, Mangalagangothri, Mangalore , India (Received 5 September 2010; final version received 25 July 2011) Hypsometric analysis is useful for understanding the geomorphic stages of a river basin. Hypsometric parameters have been evaluated and curves are prepared for all the 20 sub-basins of Kali River. Thirteen sub-basins are found to be under younger geomorphic stages with high hypsometric integral (Ea) values and subjected to recent tectonic activities. The remaining seven sub-basins are approaching mature stage and subjected to more erosion and less impacted by recent tectonic activities. Six sub-basins with lower hypsometric head values (50.56) indicate least effect of diffusive processes and another six sub-basins with medium hypsometric head values ( ) depict moderate diffusive erosion. The remaining eight sub-basins with higher hypsometric head values (40.75) indicate highest diffusive processes at their upper reaches. Lower (50.28) and higher (40.44) hypsometric toe values indicate minimum and maximum mass accumulation respectively at the sub-catchment mouth. Keywords: hypsometric analysis; Kali River; geomorphic stages; geographical information system 1. Introduction Hypsometry means relative proportion of an area at different elevations within a region and hypsometric curve depicts distribution of area with respect to altitude (Strahler 1952). Hypsometric analysis has been used to understand various forcing factors on basin topography. Weissel et al. (1994) suggest that hypsometry may reflect the interaction between tectonics and erosion and could provide a valuable geomorphic index in order to constrain the relative importance of these processes. Hypsometry may be expressed quantitatively as an integral called the hypsometric integral (Ea). Ea represents the area under the hypsometric curve. Strahler (1952) interpreted shapes of hypsometric curves by analyzing numerous drainage basins and classified the basins as youth (convex upward curves), mature (S-shaped curves which are concave upwards at high elevations and convex downwards at low elevations) and peneplain or distorted (concave upward curves). Hypsometric integral value can be used as an estimator of erosion status of watershed leading to prioritization of watershed for soil and water conservation measures (Singh et al. 2008). Singh (2008) made an attempt to study the statistical relation between *Corresponding author. ksjayappa@yahoo.com ISSN print/issn online Ó 2011 Taylor & Francis

2 554 V.J. Markose and K.S. Jayappa hypsometric integral and area of watersheds. Several studies have shown that hypsometric integrals correspond to lithological resistance and/or tectonic uplift rates (Lifton and Chase 1992, Hurtrez and Lucazeau 1999, Chen et al. 2003). Hypsometric integrals are also known to be sensitive to variables related to morphometry of the basin, such as basin area and relief (Hurtrez et al. 1999, Chen et al. 2003), basin planform, and the grid or basin perimeter based system that is applied (Lifton and Chase 1992, Willgoose and Hancock 1998). Bishop et al. (2002) found that the hypsometric integral helps in explaining the erosion taken place in the watershed during the past, due to hydrologic processes and land degradation. Lifton and Chase (1992) tested the influence of varying uplift rates on hypsometry, from a numerical model of landscape development, showing that the hypsometric integral was positively correlated to uplift rate. Hurtrez et al. (1999) investigated the sensitivity of hypsometry to digital elevation models (DEMs) of different resolutions and assessed the influence of varying drainage area on hypsometry in Siwalik Hills of central Nepal. The shape of the hypsometric curves and the Ea values provide valuable information not only on erosional stage of the basin, but also on tectonic, climatic and lithological factors of the basin (Moglen and Bras 1995, Willgoose and Hancock 1998, Huang and Niemann 2006). All the above views reveal that hypsometric analysis provides valuable information on landform evolution and tectonics. The scope of the study is limited to the evaluation of hypsometric parameters which provides valuable information on the type of erosive processes operating in the Western Ghat regions. The geographic information system (GIS) approach was used to obtain hypsometric information and to calculate the associated parameters. 2. Study area The Kali River one of the west flowing rivers of Karnataka which originates in the Western Ghat at an altitude of 900 m is a seventh order basin with a length of 184 km. It covers a total drainage area of 4837 km 2, extending from to N latitudes and to E longitudes in Uttara Kannada district of northern Karnataka, India forms the study area (Figure 1). The land mass of the river basin is situated between 0 and 1040 m above msl (Figure 2). The river flows initially towards east, then turns westward and joins the Arabian Sea near Karwar. In its course, the river loses about 350 (420 70) m elevation through waterfalls between 90 and 105 km from the origin (Figure 3). The climate of the study area is humid tropical along the coastal zone where the mean annual precipitation is around 3900 mm. The Kali River is composed of well developed drainage network ranging from first to seventh order streams (Figure 4). The major sub-basins of Kali River are: Kannadgal, Daogi, Nagihari halla and Maradi (fourth order streams); Barchi nadi, Bennemone, Birkol halla, Bargi halla, Karkia halla, Vadi halla, Bare halla, Shivapura halla, Kaiga, Kaneri and Nagi nadi (fifth order streams); Thatihalla, Sarkalihalla, Naiti holle and Vaki halla (sixth order streams); and Pandheri nadi is a seventh order stream. 3. Geology and geomorphic setting The Kali River drainage basin is composed of various lithological units of Archean age of Dharwar Super-group of rocks. The basin forms the western Dharwar Craton

3 Geocarto International 555 Figure 1. Location map of Kali River basin. of south Indian Shield and exhibits NNW SSE trending structures. Greywacke in the upstream and granodioritic to tonalitic gneisses in the downstream segment of the catchment are traversed by number of dykes and overlain by laterite and alluvium (Figure 5(A)). The intensive igneous activity by way of dyke intrusions, presence of ptygmatic, criss-cross pegmatite intrusions and highly folded granitic gneisses are the evidences of high shearing of the area. The dykes are oriented in NNW SSE, NW SE, NNE SSW and NEE SWW directions (Figure 5(B)). The schistosity is well developed in NE SW direction within ferruginous quartzites. The rocks have been folded into a series of isoclinal antiforms and synforms. The river flows down to Ghat escarpment near Karwar via two water gaps and cut across two successive parallel Banded Ferrugenues Quartizite ridges that form N S trending buttonhole structure. The main river course and its tributaries are controlled by

4 556 V.J. Markose and K.S. Jayappa Figure 2. Elevation distribution map of Kali River. Figure 3. Longitudinal profile of Kali River. lineaments at different locations. The lineaments are oriented in NW SE, NNE SSW and NEE SWW directions (Figure 5(C)). It is reported that the magmatic bodies of the Ghats canyon area near Karwar are partially metamorphosed layered intrusions in which the foliation exhibits a steep easterly dip (Vasudev and Ranganathan 1994). In Dandeli area a few km inland from the escarpment, the

5 Geocarto International 557 Figure 4. Drainage map of Kali River basin. phyllites dip consistently eastward at an angle of 528 and form hogback ridges (Durg 1969). The major part of the Kali River basin (except a narrow coastal strip and plain tableland areas on eastern part) is found in hilly regions of the Western Ghat. Considering the great height of the Ghat scarp, Valdiya (2001) opines that the megafeature cannot be just ascribed to isostatic uplift, but to neotectonic resurgence. 4. Materials and methods Topographic maps (1:50,000 scale) of the study area published by the Survey of India were georeferenced with Universal Transverse Mercator projection (WGS 1984, Zone 43 N) using ArcGIS 9.3 software. The drainage lines were digitized and stream ordering was done in accordance with Strahler s (1957) method. The entire area has been divided into 20 sub-basins with fourth to seventh orders and their boundaries were digitized using ArcGIS 9.3 software. The contours were digitized in GIS environment and elevation values as well as area enclosed between the contour and each sub-basin boundaries were calculated. The feature classes containing these values were used to plot the hypsometric curve. Many geomorphologists have classified hypsometric curve on the basis of shape geometry. Using the hypothetical hypsometric curve of Sinha Roy (2002), various parameters such as hypsometric integral (Ea), maximum concavity (Eh), coordinates of slope inflection point (I) given by a* and h* and normalized height of hypsometric curve (h) were calculated (Figure 6). Similarly three types youthful, mature and old stage of landforms have been classified by Strahler (1952, 1964) based on hypsometric curves and

6 558 V.J. Markose and K.S. Jayappa Figure 5. Geology map of Kali River basin (A); general trend of dykes (B) and lineaments (C). hypsometric integral. Hypsometric curves characterized by downward concave curve with hypsometric integral (Ea) values indicate youthful condition or inequilibrium phase, S shape curves without any evident of concavity having intermediate Ea values between 0.35 and 0.60 indicate mature or equilibrium stage, and the curves with upward concavity and Ea values indicate old or monadnock stage (Figure 7). The downward concave part of right hand side of the hypsometric curve is called toe, upward concave part of left hand side of the curve is head and upward concave segment in the centre of the curve between toe and head is called body (Willgoose and Hancock 1998, Figure 7).

7 Geocarto International 559 Figure 6. A hypothetical curve defining the hypsometric parameters which are extracted for the present study (after Sinha Roy 2002). Figure 7. Three types of hypsometric curves youthful, mature and old stage showing toe, head and body (after Strahler 1964, Willgoose and Hancock 1998). In the present study, hypsometric curves were obtained for all the 20 sub-basins of Kali River by plotting the ratio of relative area the area above a particular contour (a) to the total area (A) of the watershed along the abscissa and ratio of relative elevation the height of the given contour (h) from the base plane to the maximum basin elevation (H) on the ordinate (Figure 8). The parameters such as hypsometric integral (Ea), maximum concavity (Eh), coordinates of slope inflection

8 560 V.J. Markose and K.S. Jayappa Figure 8. Map showing 20 sub-basins extracted for hypsometric analysis (1. Naiti hole, 2. Bargi halla, 3. Sarkari halla, 4. Maradi, 5. Bennemone, 6. Kaiga, 7. Bari halla, 8. Vaki halla, 9. Birkol halla, 10. Shivapura halla, 11. Vadi halla, 12. Kaneri, 13. Nagihari halla, 14. Kannadgal nadi, 15. Daogi nadi, 16. Thati halla, 17. Karkia halla, 18. Barchi nadi, 19. Panderi nadi and 20. Nagi nadi). point (I) given by a* and h*, normalized height of hypsometric curve (h) at 0.2, 0.5, 0.8 and 0.9 (20%, 50%, 80% and 90%) which provide the elevations relative to maximum height that cover the specific proportion of the catchment area were calculated (Table 1). 5. Results and discussions Results of the study are discussed under the sub-headings hypsometric curve shape, hypsometric head and toe and hypsometric integral and slope inflection point Hypsometric curve shape For all the 20 sub-basins of Kali River, hypsometric parameters are calculated and hypsometric curves have been prepared (Table 1, Figure 9). Hypsometric curves are distinguished into three groups based on their shape. The first group is characterized by concave upward curves with an average Ea value of 0.32 representing mature to late mature stage of landforms. The second group of curves is characterized by concave convex shape with an average Ea value of 0.51 representing fluvial and slope wash processes of landforms. The third group of curves is characterized by concave downward and convexity in the toe part with high Ea values (average 0.63) represents youthful stage of landforms.

9 Geocarto International 561 Table 1. Hypsometric parameters hypsometric integral (Ea), normalized height of hypsometric curve (h) at 0.2, 0.5, 0.8 and 0.9, maximum concavity (Eh) and coordinates of slope inflection point (I) given by a* and h* of all the 20 sub-basins of Kali River. S. No. Name Area (sq. km) Ea Height of hypsometric curve (h) Coordinates of (I) at 0.2 at 0.5 at 0.8 at 0.9 Eh a* h* 1 Naiti hole Bargi halla Sarkari halla 4 Maradi Bennemone Kaiga Bari halla Vaki halla Birkol halla Shivapura halla 11 Vadi halla Kaneri Nagihari halla 14 Kannadgal nadi 15 Daogi nadi Thati halla Karkia halla Barchi nadi Panderi nadi Nagi nadi Hypsometric curves of Naiti hole, Bargi halla, Sarkari halla, Karkia halla, Barchi nadi, Panderi nadi and Nagi nadi sub-basins (Nos. 1 3 and 17 20) belong to first group. Of these, Karkia halla, Panderi nadi and Nagi nadi show downward concavity in the toe side. All these seven sub-basins show high relative relief which indicates high internal dissection and steep slope. Karkia halla, Barchi nadi, Panderi nadi and Nagi nadi are located in the upper part and the remaining three are located in the lower part of the Kali River basin (Figure 8). Shape of this type of curves indicates that the fluvial process is dominated in the catchment which is evidenced by fluvial deposits and incision of bed rock (Figure 10(A) and (B)). Chattopadhyay et al. (2006) suggest that concave hypsometric curve is an indicator of an area predominated by erosion and the eroded materials are accumulated in the downstream. Hypsometric curves of Maradi, Bennemone, Kaiga, Bari halla, Vaki halla, Birkol halla and Shivapura halla (Nos. 4 10) belong to second group. This type of curve indicates that upper part of the sub-basins is favourable for dominance of slope wash, may be due to the lithological differences (Ciccacci et al. 1992). Hypsometric curves of Vadi halla, Kaneri, Nagihari halla, Kannadgal nadi, Daogi nadi and Thati halla (Nos ) belong to third group. These sub-basins (except Thati halla) are found to be located in the scrap regions of Western Ghat (Table 1; Figures 8 and 9).

10 562 V.J. Markose and K.S. Jayappa Figure 9. Hypsometric curves of twenty sub-basins. Concave upward curves (Nos. 1 3 and 17 20) belong to first group, downward concave curves (Nos. 4 10) belong to second group and concave downward curves with convexity in the toe part (Nos ) belong to third group Hypsometric head and toe The values of hypsometric head and toe have significant importance of landscape evolution. It is observed that higher the hypsometric head i.e. h (0.2), greater is the influence of diffusive processes at the upper reaches of the sub-catchment. On the other hand, higher the hypsometric toe i.e. h (0.8), greater is the mass accumulation

11 Geocarto International 563 Figure 10. (A) Fluvial deposits indicating dominance of fluvial process; (B) Bedrock incision in the Kaneri river bed; (C) Folds in the middle part of Kaneri River and (D) Parallel joints are manifestations of neotectonics. at the sub-catchment mouth, derived mainly through fluvial transport (Sinha Roy 2002). Based on hypsometric head (h at 0.2), it has been observed that the subbasins Naiti hole, Bargi halla, Karkia halla, Barchi nadi, Panderi nadi and Nagi nadi belonging to first group with lower values of hypsometric head (50.56) indicate least diffuse processes at the upper reaches of these sub-basins, whereas the sub-basins Bennemone, Kaiga, Vaki halla, Birkol halla and Shivapura halla of second group, and Nagihari halla, Vadi halla and Daogi nadi sub-basins of third group with higher hypsometric head (40.75) indicate predominant diffusive processes at the upper reaches of these sub-basins. The remaining six sub-basins Sarkari halla (first group), Maradi, Bari halla (second group), Kaneri, Kannadgal nadi and Thati halla (third group) with moderate values ( ) of hypsometric head indicate moderate diffusive erosion at the upper reaches. Considering the toe values, those belonging to second group except Bari halla, show lower values (50.28) indicating minimum mass accumulation at the subcatchment mouth. All the sub-basins belonging to third group (except Thati halla) show higher values (40.44), indicating greater mass accumulation at the subcatchment mouth. Shape of toe reflects the form of lateral contribution and the degree of branching within the catchment (Willgoose and Hancock 1998). Increased branching at toe region leads to development and enlargement in size of toe catchment.

12 564 V.J. Markose and K.S. Jayappa 5.3. Hypsometric integral and slope inflection point Hypsometric integral controls the shape of a hypsometric curve and thereby provides clues for landform evolution (Sinha Roy 2002). Normally, downward concave hypsometric curves show higher hypsometric integral. All the 20 sub-basins are classified into four groups based on the hypsometric integral values. Six sub-basins namely Naiti hole, Bargi halla, Karkia halla, Barchi nadi, Panderi nadi and Nagi nadi (Nos. 1, 2 and 17 20) with Ea values belong to first group. Naiti hole and Bargi halla sub-basins are located near to the coast and remaining ones are in the upper part of the basin. Three sub-basins Sarkari halla, Maradi and Thati halla (Nos. 3, 4, and 16) with an average Ea value of 0.44 belong to second group. Seven sub-basins Bennemone, Kaiga, Bari halla, Vaki halla, Birkol halla, Shivapura halla and Kaneri (Nos and 12) with an average Ea value of 0.52 belong to third group. The remaining four sub-basins Vadi halla, Nagihari halla, Kannadgal nadi and Daogi nadi (Nos. 11, 13 15) with an average Ea value of 0.64 come under fourth group (Table 1). High values of Ea are possibly related to young, active tectonics and low values of Ea are related to older landscapes that have been more eroded and less impacted by recent tectonic activities (Hamdouni et al. 2008). Lower Ea values also indicate mass removal of materials by erosion and older landforms. Sudden change in channel configuration and presence of gorges in middle part of Kaneri River is an indication of the tectonic control of this region (Figure 11). Incised channels, folds and parallel joints in the middle part of Kaneri River were observed during the field studies (Figure 10(B) (D)). The position of maximum concavity (Eh) of sub-basins show mixed character (Table 1). Eh values of the seven sub-basins of first group (Figure 8) are positive, which indicates mature stage of landforms and more eroded upland areas. Whereas those belonging to second and third groups show negative Eh values, indicating young landforms and less eroded upland areas. As far as one of the slope inflection points i.e. a* values are considered, eight sub-basins (Nos. 1, 3, 4, 14, 17 20) show lower values (50.23), seven sub-basins (Nos. 2, 5, 6, 8 10 and 15) show moderate values ( ) and the remaining five sub-basins (Nos. 7, and 16) show higher values (40.8). Regarding another slope inflection point (h*) values are considered, four sub-basins (Nos. 2, 11, 15 and 16) show lower values (50.28), eight sub-basins (Nos. 6, 7, 10, 12, 14 and 18 20) show moderate values ( ) and the remaining eight sub-basins (Nos. 1, 3 5, 8, 9, 13 and 17) show higher values (40.62). Lower the value of a*, greater is the extent of subduced topography approaching Davision style of peneplain and lower the value of h*, higher is the degree of peneplanation (Sinha Roy 2002) Potential lithological controls Lithological variations can potentially affect the hypsometry of drainage basins in complex ways (Walcott and Summerfield 2008). In our study area, there are two main spatial scales at which significant lithological variations are evident. Upper part of the basin consists of greywacke argillite and granite, whereas lower part of the basin consists of migmatite and granodioritic to tonallite gneisses. We computed area of main lithology, i.e. lithology that appears most often and calculated its percentage sub-basin wise. Perez-Pena et al. (2009) have followed similar method; but instead of calculating main lithology for sub-basin, they have used regular square

13 Geocarto International 565 Figure 11. Sudden change in the channel flow of Kaneri River and gorge area (FCC of IRS P6 LISS-III). grids. The results show that sub-basin occupied by migmatite and metabasalts have relatively higher Ea (average 0.39) values except two sub-basins Naiti holle and Bargi halla which are located close to river mouth. Sub-basins occupied by greywacke argillite and granite have relatively lower Ea (average 0.35) values except three Vaddi halla, Kannadgal nadi and Daogi sub-basins. These three sub-basins are small in size and located in the lower part of the basin. Presence of a thick, resistant unit in the headwaters of a catchment will tend to decrease its hypsometric integral, while exposure of such a unit near the mouth of the basin will tend to increase its hypsometric integral (Walcott and Summerfield 2008). This fact is clearly found in the present study area where the sub-basins are occupied by migmatite and metabasalt showing relatively higher Ea values. However, this influence is not enough to explain great variations in relative high or low Ea values because of the absence of adequate geological information Hypsometric integral and basin area Willgoose and Hancock (1998) and Hurtrez et al. (1999) suggested that in small basins the hypsometric curve is convex and the value of the hypsometric integral approaches unity, indicating a predominance of hill slope processes, whereas in large basins the curves are concave, the integral approaches zero and fluvial processes predominate. In order to check the scale dependency, statistical analysis has been carried out between area and hypsometric integral. Area of the sub-basins varies from km 2 to km 2. The regression analysis reveals that hypsometric integral (Ea) and area of all the 20 sub-basins show negative relation (r 2 ¼ 0.028). This is because of asymmetric distribution of area of sub-basins, i.e. relatively larger ones are located in the upper part compared to the lower part. To solve this problem, the entire data set of all the 20 sub-basins were classified into four area classes based on natural breaks method and then regression analysis was carried out. The average Ea values of first area class is 0.48 (539 km 2 ), 0.55 ( km 2 ) for second, 0.37 ( km 2 ) for third and 0.45 (4172 km 2 ) for fourth area classes. The regression analysis reveals that Ea and area have positive relation in small basins, whereas as the area increases the relation becomes negative and weak (Figure 12(A) (D)). This

14 566 V.J. Markose and K.S. Jayappa Figure 12. Statistical relation between area and hypsometric integral of sub-basins of four area classes. Note that positive relation exits in class 1 (A) and negative relation in class 2, 3 and 4 (B, C and D). confirms that the hypsometric integral is controlled by basin area in small sub-basins rather than larger ones. 6. Conclusion In order to understand the type of erosive processes and relative age of land forms, hypsometric analysis has been carried out for all the 20 sub-basins of Kali River basin. Several parameters [hypsometric integral (Ea), maximum concavity (Eh), coordinates of slope inflection point (I) given by a* and h* and normalized height of hypsometric curve (h)] were extracted from the hypsometric curves and used for understanding the landform characteristics. Hypsometric parameters provide strong indication regarding tectonic activities in the sub-basins which has been confirmed during the field observations. Seven sub-basins (Naiti hole, Bargi halla, Sarkari halla, Karkia halla, Barchi nadi, Panderi nadi and Nagi nadi) belonging to first group of Kali River catchment show upward concave hypsometric curve with low Ea values (average 0.32) indicating mature to late mature topography. These seven sub-basins (except Sarkari halla) with lower values of hypsometric head indicate less diffuse processes at their upper reaches and approaching the equilibrium stage of landform evolution. The remaining 13 sub-basins show downward concave curve with high Ea values (average 0.55) indicating fluvial and slope wash processes of landforms. These 13 sub-basins fall in the younger stage of landform evolution. Statistical relation between the area and Ea values reveals that Ea is controlled by area of smaller sub-basins rather than larger ones. As far as lithology is concerned,

15 Geocarto International 567 sub-basins occupied by migmatite and metabasalt show relatively higher Ea values compared to those sub-basins occupied by greywacke argillite. Five sub-basins Bennemone, Kaiga, Vaki halla, Birkol halla and Shivapura halla - of second group and three sub-basins Nagihari halla, Vadi halla and Daogi nadi of third group with higher hypsometric head values indicate dominance of diffusive processes in their upper reaches. Only one sub-basin, i.e. Bari halla of second group with high toe value indicates greater mass accumulation by fluvial transport and all other sub-basins of this group show lower values (50.28) indicating minimum mass accumulation at their mouth. Four sub-basins Vadi halla, Nagihari halla, Kannadgal nadi and Daogi nadi belonging to third group show higher toe values (40.44) depicting greater mass accumulation at their mouth. Acknowledgements The authors wish to thank the University Grants Commission (UGC) of New Delhi for providing the financial assistance in the form of a Major Research Project (No.F.33-45/ 2007(SR)). The authors also acknowledge both the anonymous reviewers for their comments and suggestions which improved the quality of the manuscript. References Bishop, M.P., et al., Geomorphic change in high mountains: a western Himalayan perspective. Global and Planetary Change, 32, Chattopadhyay, S., Sajikumar, S., and Chattopadhyay, M., Landscape evolution in parts of Vamanapuram drainage basin, Kerala a hypsometric approach. Journal of Geological Society of India, 68, Chen, Y.C., Sung, Q., and Cheng, K., Along-strike variations of morphotectonic features in the Western Foothills of Taiwan: tectonic implications based on streamgradient and hypsometric analysis. Geomorphology, 56, Ciccacci, S., et al., Relation between Morphometric characteristics and denudational processes in some drainage basins of Italy. Annals of Geomorphology, 36, Durg, N.L., A structural study of the phyllites near Dandeli, Mysore state. Quarterly Journal of Geology, Mining and Metallurgical Society of India, 41, Hamdouni, R.El., et al., Assessment of relative active tectonics, Southwest Border of Sierra Nevada (southern Spain). Geomorphology, 96 (1 2), Huang, X.J. and Niemann, J.D., Modelling the potential impacts of ground water hydrology on long-term drainage basin evolution. Earth Surface Processes and Landforms, 31, Hurtrez, J.E. and Lucazeau, F., Lithological control on relief and hypsometry in the Herault drainage basin (France), Comptes Rendues Acade mie des Sciences de la terre et des planets. Earth and Planetary Sciences, 328 (10), Hurtrez, J.E., Sol, C., and Lucazeau, F., Effect of drainage area on hypsometry from an analysis of small-scale drainage basins in the Siwalik Hills (central Nepal). Earth Surface Processes and Landforms, 24, Lifton, N.A. and Chase, C.G., Tectonic, climatic and lithologic influences on landscape fractal dimension and hypsometry: implications for landscape evolution in the San Gabriel Mountains, California. Geomorphology, 5, Moglen, G.E. and Bras, R.L., The effect of spatial heterogeneities on geomorphic expression in a model of basin evolution. Water Resources Research, 31, Singh, O., Sarangi, A., and Sharma, M.C., Hypsometric integral estimation methods and its relevance on erosion status of North-Western lesser Himalayan watersheds. Water Resource Management, 22, Singh, T., Hypsometric analysis of watersheds developed on actively deforming Mohand anticlinal ridge, NW Himalaya. Geocarto International, 2, Perez-Pena, J.V., et al., Differentiating geology and tectonics using a spatial autocorrelation technique for the hypsometric integral. Journal of Geophysical Research Earth Surface, 114, F02018.

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