INTRODUCTION

The Himalayan orogeny is a distinctive example of the intercontinental collision between the Indian and Eurasian plates at ~55 Ma [19, 38, 65–67]. The convergence and collision is largely accommodated by southward tectonic transport of thrusts and faults which is expressed in associated geomorphic features and formed three major north-dipping thrust systems known as Main Central Thrust (MCT), Main Boundary Thrust (MBT) and Himalayan Frontal Thrust (HFT) from north to south respectively [18, 53]. The MCT separates the Lesser Himalayan sequences in Kumaun region from the Higher Himalaya in the north and further in the south it is delineated from the Siwalik (sub-Himalaya) by MBT, respectively [24, 42].

Morphometric analysis in association with fluvial landforms study has been used to ascertain the tectonic instability/stability in the Gola and Kalsa River valleys of the Kumaun Lesser Himalaya. Morphotectonic study plays an important role in deciphering the effects of tectonic activity in the geomorphic evolution of the drainage basins. The study area lies between latitude 28°21′44″ and 29°29′24″ N and longitude 79°14′10″ and 79°49′17″ E and also marked in the Survey of India toposheet nos. 53 O/11, 53O/12, 53 O/15, 53 O/16, on 1 : 50 000 scale, covers an area of about 640.76 km2 with 494.55 and 146.21 km2 areas of Gola and Kalsa River basins separately. Gola River originates in the Sattal lakes (Paharpani) of Uttarakhand and meets in the Ramganga River near Bajpur about 15 km northwest of Bareilly in Uttar Pradesh, and its catchment has been affected by several landslides, as a result of soil erosion and deforestation. The river bed of Gola, after hitting the plain near Haldwani has been facing soil erosion, due to excessive quarrying. The study area from South to North, comprises Piedmont zone, Siwalik belt, Outer Lesser Himalaya and parts of Almora Crystalline zone. Major thrusts present in the area are Himalayan Frontal fault (HFF), Main Boundary Fault (MBF) and South Almora Thrust (SAT). The present study area comprises the frontal part of the Kumaun Sub-Himalaya, geomorphologically bounded by the Gola River in the east and the Kalsa River in the west (Fig. 1). The area has a complex physiography, mainly consisting of mountains, structural hills and valleys, terraces, piedmont areas etc.

Fig. 1.
figure 1

Geological and tectonic map of the study area showing Gola and Kalsa River basins, major lithologies and major tectonic planes/thrusts (modified after [6]).

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The main objective of the present study is to know the effect of tectonic activity in the geomorphic evolution of the drainage basins. Some feature like bending and offsetting of streams, linear ridges, pressure ridges, beheaded streams, offset drainage, triangular facets, open rifts and prominent scarps, and their alignments in certain directions, are difficult to map in the field but could be easily deciphered from remote sensing image.

GEOLOGICAL SETTING

The study area comprises the rocks of Siwalik Group, Outer Lesser Himalaya and Almora Group. It exposes mainly between two major litho-tectonic subdivision of the Himalaya, namely, Mukteshwar Dislocation (MD) [6] in the north and Himalayan Frontal Thrust (HFT) in the south. The Almora Crystalline Zone (ACZ) is one of the largest and intensely deformed thrust sheets of the Lesser Himalaya. ACZ trends WNW–ESE and is separated from the Damtha–Tejam Group of rocks in the north and the sedimentary Krol belt in south by the North Almora Thrust Zone (NATZ) and South Almora Thrust (SAT), respectively [2, 3, 25, 60]. The southern limb of the Almora synform with north dipping metamorphic rocks, has been divided into two: (i) the lower Ramgarh Formation (dominantly constituted of mylonites, schists, inter-bedded quartzite and phyllites) in the south and (ii) the upper Mukteshwar Formation (having quartzites, garnetiferous schists and subordinate phyllites and gneisses) in the north separated by MD or Ramgarh Thrust/Uprari Thrust [2, 6, 11, 60].

The Main Boundary Thrust (MBT) constitutes the boundary between the Cenozoic rocks of the Sub-Himalaya (Siwaliks) and that of the Precambrian Lesser Himalaya (a thick pile of highly folded upper Precambrian sedimentary units with a few outcrops of crystalline rocks) [35, 60]. The southernmost thrust is the Himalayan Frontal Fault (HFF) that separates the ruggedly youthful Siwalik Hills (about 7 km thick) made up of late Tertiary to early Quaternary molasses from that of the recent alluvium of the Gangetic plain [41, 43]. These Siwalik sediments are deposited during middle Miocene and Pleistocene by rivers flowing southwards from the high Himalayan hills, while the Himalaya was being uplifted [14, 15]. The study area comprises the Lower and Middle succession of Siwalik Group [8, 29, 49]. The Siwalik sequence is comprised of thick sandstone-mudstone couplet (purple, dark to pale brown and compact) nodular siltstones and very fine-grained rippled sandstones whereas the lower part is dominated by greyish to pale brown fine sandstones [8, 29]. The southernmost part of the area is marked by the alluvium of the Ganga plain.

MATERIALS AND METHODS

This work is based on morphometric analysis of Gola and Kalsa River basins using common morphometric parameters and analyses of landforms to determine the impact of tectonics in the development of various landforms, erosion processes and consequent drainage development. In order to approach this, SOI toposheet nos. 53 O/11, 53O/12, 53 O/15, 53 O/16 at the scale of 1 : 50 000 and the ASTER DEM data derived from Shuttle Radar Topography Mission (SRTM) is used to prepare the drainage map of the study area. The entire area has been demarcated with the help of Arc-GIS 10.3 software and topographical maps are rectified/referenced geographically assigning Universal Transverse Mercator (UTM), World Geodetic System (WGS dating from 1984 and last revised in 2004) and 43N Zone Projection System. SRTM data is also converted into UTM projection.

The drainage network of Gola and Kalsa River Basins are digitized in GIS environment and quantitative analyses of morphometric parameters of the basin like stream orders (assigning unique ids for them as 1st order, 2nd order, 3rd order and so on), stream length and stream numbers have been calculated and the natural drainage system network in SOI topographic sheets were later updated using DEM and FCC obtained from IRS LISS III satellite data in spatial analysis toolbox of ARC GIS environment. An integrated use of multispectral satellite data, digital elevation model (DEM) and survey of India topographical sheets were utilized for generation of database and extraction of various drainage parameters.

MORPHOMETRIC ANALYSIS

Morphometric analysis of Gola and Kalsa River basins has been carried out to determine the drainage characteristics, basin geometry, lithological variations and effect of tectonic movements. The geomorphology of an area is an imprint of the several geological processes active there and has been focused on the development of quantitative physiographic methods to describe the evolution and behavior of surface drainage networks [1, 23, 31]. Along with the geomorphic evidences of neotectonics and active tectonic activities, an attempt has also been made to represent the study area geomorphometrically, which helps to understand the tectonic conditions of the area, particularly in recent times.

All the morphometric parameters of Gola and Kalsa River basins have been categorized into three broad classes and are described as Linear, Areal and Shape parameter.

Linear Parameters

(1) Stream order (Nu) is the classification of streams based on their hierarchical position within a drainage basin which is a useful indicator of stream size, discharge and drainage area. Ordering of streams is initiated from the fingertip tributaries, which lacks their own feeders [55]. The number of streams (N) of each order (u) for Gola and Kalsa River basin is given in details in Tables 1 and 2. The details of the stream characteristics confirm HORTON’S [23] first law of stream numbering which states that the number of streams of different orders in a given drainage basin tends closely to approximate an inverse geometric ratio. The maximum no. of streams in the Gola River basin is 246 for sub-basin no. 8 with 5th order. Minimum no. of streams in a sub-basin is 6 and is present in sub-basin no. 21 with 2nd order. Maximum no. of streams in the Kalsa River basin is calculated to 86 for the sub-basin no. 14 which is a 4th order basin. The minimum no. of streams calculated in Kalsa River basin is 4 for sub-basin nos. 5, 6 and 21. Drainage network of Gola and Kalsa River basins has been presented in Figure 2.

Table 1.   Linear parameters of the Gola River basin, Kumaun Lesser Himalaya, Uttarakhand
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Table 2.   Linear parameters of the Kalsa River basin, Kumaun Lesser Himalaya, Uttarakhand
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Fig. 2.
figure 2

Map showing drainage network of Gola and Kalsa River basins, Kumaun Lesser Himalaya, Uttarakhand.

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(2) Stream length (Lu) is the total length of individual stream segments of each order. In the present investigation, the maximum stream length is of the first order stream which decreases with increasing stream order. This can be attributed to flowing of the stream from high altitude, lithological variation, moderately steep slopes and possible uplift across the drainage basin [13, 47, 50]. The total stream length of Gola River basin is found to be 897.50 km and that of Kalsa River basin 291.91 km. The stream lengths of sub-basins are presented in Tables 1 and 2. Stream length is calculated for all the sub-basins of Kalsa and Gola River from the attribute table of the corresponding layers in the ArcGIS. In Gola River basin maximum value of total stream length is 143 km for sub-basin no. 8 and minimum is 3 km for sub-basin no. 24 and in the Kalsa River basin, longest total stream length is 63.5 km for sub-basin no.14 and the smallest total stream length is calculated 2.6 km for sub-basin no. 5. Values of stream lengths are higher for Gola River basin than of Kalsa River basin.

(3) Stream length ratio (Rl) has been defined as the ratio of mean stream length of an order to the next lower order stream segment [23]. The stream length ratios have been calculated as:

$${\text{Rl}} = {\text{Lu}}/{\text{Lu}} - 1,$$

where Lu is the stream length of an order u, Lu – 1 is the stream segment length of next lower order.

The mean stream length ratio of the Gola River and Kalsa River basins are 0.67 and 0.68 respectively. The Rl between streams of different order reveals that the Rl for sub-basins ranges between 0.33–2.81 (Gola River basin) and 0.25–1.50 (Kalsa River basin) respectively.

(4) Bifurcation ratio (Rb). It is the ratio of number of streams of a given order (Nu) to the number of streams of the higher order (Nu + 1) [23, 56] and computed as:

$${\text{Rb}} = {\text{Nu}}/{\text{Nu}} + 1.$$

The bifurcation ratio is strongly controlled by various geological parameters and their higher values indicate towards the dominance of structural control and complexity in the area thereby confirming active tectonics [4, 5, 64].

The bifurcation ratio for Gola River basin varies from 1.83 to 7.50 and for Kalsa River basin 2.0 to 7.0 respectively. The mean bifurcation ratios for Gola and Kalsa River basins are 3.31 and 3.94 respectively. Sub-basin 3 and 36 (0.35 and 0.33) have low value of stream length ratio while the low value of bifurcation ratio in sub-basin 7 and 24 (2 and 1.83), is indicative of comparative stability in these sub-basins.

For the Kalsa River basin, the high value of bifurcation ratio is observed in sub-basin 7 and 8 (7.00 and 6.75) respectively. The values of stream lengths in sub-basins 3 and 21 are 0.25 and 0.41 and bifurcation ratio in sub-basins 4 and 17 is 2.00 and 2.25 respectively.

(5) RHO coefficient is the ratio between the stream length ratio (Rl) and the bifurcation ratio (Rb) [23]:

$${\text{RHO}} = {\text{Rl/Rb}}{\text{.}}$$

It is an important parameter to understand the evaluation of the storage capacity of the drainage network [23]. The mean RHO coefficient of the Gola River basin is 0.22 and of Kalsa River basin is 0.21, while the RHO coefficient of the sub-basins varies between 0.06–0.99 for Gola River and 0.05‒0.56 for the Kalsa River (Fig. 2).

Areal Parameters

The two-dimensional properties of a drainage basin are defined by the areal parameters in which the stream frequency (Fs), drainage density (Dd), drainage texture (Rt) are important. All these parameters for Gola and Kalsa River basins are presented in Tables 3 and 4. Drainage density, drainage texture and stream frequency are the measure of the degree of fluvial dissection of terrain and is influenced by natural factors like resistance to erosion of rocks, infiltration capacity, lithology, climate, vegetation, rock and soil types, relief, surface roughness and stage of development of the basin.

Table 3.   Areal parameters of the Gola River basins, Kumaun Lesser Himalaya, Uttarakhand
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Table 4.   Areal parameters of the Kalsa River basin, Kumaun Lesser Himalaya, Uttarakhand
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(1) Area, perimeter, and basin length. The Gola and Kalsa River basins cover an area (A) of 494.55 and 146.21 km2 respectively, having perimeter (P) of 423.84 and 181.96 km respectively. In case of sub-basins, the area ranges from 1.02 (for sub-basin no. 25) to 47.76 km2 (sub-basin no. 8) for Gola River basin and 0.64 (sub-basin no. 5) to 22.42 km (sub-basin no. 14) for Kalsa River basin respectively. Similarly, the perimeter for these sub-basins ranges between 4.28 (sub-basin no. 25) to 33.24 km (sub-basin no. 8) for Gola River basin and 3.70 (sub-basin no. 1) to 21.42 km (sub-basin no. 14) for Kalsa River basin respectively. The area and perimeter of all the sub-basins of Gola and Kalsa River basins are given in Tables 3 and 4. The basin length (L) corresponds to the maximum length of the basin and sub-basins measured parallel to the main drainage line [34]. The total basin length for Gola and Kalsa River basins are 164.64 km and 67.49 km respectively (Tables 3, 4).

(2) Stream frequency (Fs; also known as channel frequency) is the total number of stream segments of all orders per unit area of the basin [22]. The stream frequency is associated with the permeability of bedrocks, infiltration capacity and relief and steepness of the sub-basins [64]. Higher stream frequency suggests poor infiltration and higher relief while lower stream frequency suggests higher permeability of bedrocks and low relief in the area.

$${\text{Fs}} = \Sigma {\text{Nu}}/{\text{A}},$$

where ƩNu is the total number of stream segments of all orders, and A is the area of the basin.

The mean stream frequency (Fs) values for Gola and Kalsa River basins are 5.15 and 4.64 km–2.

While for the sub-basins it varies from 1.73–10.0 (Gola River basin) and 2.16–10.98 (Kalsa River basin) (Tables 3 and 4). The presence of relatively higher Fs values for the sub-basins in the study area are indicative of relatively higher relief and lower infiltration capacity of the bedrock.

(3) Drainage density (Dd). It is the ratio of the total length of streams of all orders to the area of the drainage basin. It is an expression of the spacing of channels within a basin [22] and provides a numerical measurement of landscape dissection and runoff potential [64]. Dd is expressed as:

$${\text{Dd}} = \Sigma {\text{Lt}} = {\text{A}},$$

where ƩLt is the total length of all the ordered streams, A is the area of the basin.

High drainage density is the resultant of weak or impermeable subsurface material, sparse vegetation and mountainous relief whereas low drainage density generally results in the areas of highly resistant or permeable subsoil material, dense vegetation and low relief [40]. The amount and type of precipitation influence directly the quantity and character of surface runoff. Low Dd leads to coarse drainage texture while high Dd leads to fine drainage texture. Amount of vegetation and rainfall absorption capacity of soils, which influences the rate of surface runoff, affects the drainage texture of an area [13]. The mean Dd of the Gola and Kalsa River basins are 3.16 and 3.09 km–1 respectively while the Dd of all sub-basins of Gola and Kalsa River (Tables 3, 4). The distribution of the Dd of the study area have been shown in Figure 3.

Fig. 3.
figure 3

Map showing range of Drainage density in Gola and Kalsa river basins, Kumaun Lesser Himalaya, Uttarakhand.

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For Gola river basin, Sub-basins 16 and 23 (Dd—4.61 and 4.24 and Rt—33.30 and 42.39) have higher values which indicate that drainage texture is fine. Whereas sub-basin 34 and 37 (Dd—2.26 and 1.70 and Rt—5.29 and 2.93) have low values which is a cause of incompetent or highly permeable lithology and low relief. It indicates the coarse drainage texture. For Kalsa River basin sub-basin 1 (Dd—5.15 and Rt—56.73) and sub-basin 20 (Dd—2.24 and Rt—4.84) have high and low value respectively.

(4) Drainage texture (Rt) is the ratio of the total number of stream segments of all orders in the river basin to the perimeter of the basin [23]. Drainage texture has been categorized as (<2) very coarse, (2–4) coarse, (4–6) moderate, (6–8) fine, (>8) very fine [51].

$${\text{Rt}} = {\text{Nu}}/{\text{P}}{\text{,}}$$

where Nu is the total no. of streams of all orders, P is the perimeter (km).

Rt for the entire Gola and Kalsa River basins are 17.16 and 15.25 respectively. For Gola River basin the sub-basin 37 (coarse texture), 34 (moderate texture) and all other sub-basin show very fine texture while for Kalsa River basin, sub-basin 20 (moderate texture), 21 (Fine texture) and other show very fine texture.

Shape Parameters

(1) Elongation ratio (Re) is calculated as the ratio between the diameter (D) of a circle of the same area as the drainage basin and basin length (L) [48] and is calculated as:

$${\text{Re}} = {\text{D/L}} = 1.128\surd {\text{A/L}}.$$

The values of Re vary from zero (highly elongated shape) to one (circular shape). The lower value of Re indicates youth stage of river basin which are controlled by tectonic activity whereas higher value signifies equal erosion (11, 35, 66). Re for the entire Gola and Kalsa River basins are 0.25 and 0.65 respectively. The Re values for both the basins indicate their elongated shape with high relief and steep slopes. The Re values for sub-basins of Gola and Kalsa River are given in Tables 3 and 4.

(2) Circulatory ratio (Rc). It is defined as the ratio of basin area (A) to the area of circle having the same perimeter as that of the basin [37, 56].

$${\text{Rc}} = 4\pi {\text{A/}}{{{\text{P}}}^{2}},$$

where A is the the area of the basin and P is the the perimeter of the basin.

The values of circularity ratio vary between 0 to 1. Higher the value of Rc, more circular is the basin. It indicates the stage of the basin. It’s low, medium and high values describe youth, mature and old stages of the lifecycles of the tributary basins [52]. The Rc values for the entire Gola and Kalsa River basins are 0.65 and 0.60 respectively while those of other sub-basins are shown in Tables 3 and 4.

(3) Form factor (Rf) is expressed as a ratio between the area of the basin (A) and the square of the drainage basin length (L2) and defines the shape of the drainage basin [23]. Rf values vary between 0.1 and 0.8. Higher values represent an almost circular basin while the ellipticity of basin increases with its decreasing values. It is expressed as:

$${\text{Rf}} = {\text{A}}/{{{\text{L}}}^{2}}.$$

The basins with high Rf values have high peak flows of shorter duration, whereas lower peak flows of longer duration are related with the basins having low Rf Values [13]. The Rf values for the entire Gola and Kalsa River basins are 0.35 and 0.35 respectively that show elongated basins shapes, while those of other sub-basins are shown in Tables 3 and 4.

For Gola River basin, the higher values of Re, Rc and Ff of sub-basins (1, 23, 30, 38, 39) show the circular shape whereas their low values for sub-basins (17, 21, 22) indicate elongate shape (Table 3). For Kalsa River basin, sub-basins (3, 13) have higher value and sub-basins (6, 16) have minimum values (Table 4).

(4) Asymmetric factor (Af) is useful for detecting tectonic tilt in a drainage basin area [16, 21, 26]. Af values greater than 50 indicate that the mainstream has shifted downstream left side of the drainage basin whereas Af values less than 50 indicate right side downstream shift of the mainstream to the basin [26, 46, 59]. The Af values for the entire Gola and Kalsa River basins are 137.11 and 55.17 respectively while those of other sub-basins are shown in Tables 3, 4 and the range of Asymmetry factor in Gola and Kalsa River basins have been presented in Fig. 4.

Fig. 4.
figure 4

Map showing the range of Asymmetry factor in Gola and Kalsa River basins, Kumaun Lesser Himalaya, Uttarakhand.

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The range of asymmetry factor for Gola and Kalsa River basins vary from 2.13–1171.73 and 20.57–136.57 respectively. Sub-basins 26 and 8 (Gola River) and 11 and 10 (Kalsa River) having highest and lowest values respectively, indicates that they are structurally controlled and tectonically active. The sub-basins (2‒7, 10, 19, 21‒27, 29, 30, 31, 39, 40) of Gola River basin, suggest that the mainstream has sifted downstream right side of the basin and all the other sub-basin indicate that the mainstream shifted downstream left side of the basin. For Kalsa river basin, sub-basins (2, 8, 9, 11, 14, 16‒19, 21) indicates that the mainstream has sifted downstream right side of the basin and all the other sub-basin indicate that the mainstream shifted downstream left side of the basin except sub-basin 12 because it has Af value closer to 50.

LINEAMENT ANALYSIS

Lineaments are the linear surface features which differ distinctly from the patterns of adjacent features and reflect expressions of the subsurface geological structures [17]. On the basis of the detailed study of lineaments were identified and an attempt was made to evaluate the effect of tectonic activity and geomorphic development of the area. Lineament trends of varying magnitude and direction are recognized over the entire study area (Fig. 5). The trends of these lineaments correspond to the NE-SW as major lineament trends along with few NNE-SSW and NW-SE have identified in the Gola and Kalsa River basin.

Fig. 5.
figure 5

Major lineaments trend and the rose plot of the Gola and Kalsa River basins.

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GEOMORPHOLOGY EVIDENCE OF ACTIVE TECTONICS

Crustal readjustment and recurrent seismicity in the Himalaya are a consequence of the continued northward movement of the Indian plate [39, 62, 63]. Such adjustments are recorded in the form of neotectonic activity experienced in different segments of the Himalaya and in turn are manifested in distinct landforms [7, 12, 61]. The recent tectonic activity in the study area is common and is evident in the form of several geomorphic features like triangular facets, asymmetrical river terraces, changing river courses, entrenched meanders, river gorges and landslides.

The Outer Himalaya shows excellent evidences of neo-tectonic activities [10]. The areas around MBT and HFT are marked by the imprints of neotectonic activities witnessed as thrusting of the older rocks over recent colluvial fan deposits, deflected and meandering streams, fault scarps and waterfalls and have made the region prone to the landslides [30, 41].

Seismicity

The eastern part of Kumaun Himalaya is seismically one of the most active segments [27, 28, 44]. In the Kumaun Himalaya, the seismicity is concentrated mainly between the MBT and MCT zones during the last few years [44, 45]. Current earthquake studies indicate that the majority of earthquakes lie between the MBT and MCT, as evident from aftershock studies of two strong recent earthquakes, 1991 of Uttarkashi and 1999 of Chamoli [32, 45]. The geological units in the area are separated by major tectonic planes like HFF, MBT and SAT along with several transverse faults.

Triangular fault facets and cones are well developed along Gola and Kalsa River basin which is usually associated with the normal sense of faulting [58]. These are the physiographic feature having a broad base and an apex pointing upward specifically the face on the end of a faceted spur, or triangular shaped steep sloped hill or cliff formed usually by the erosion of a fault truncated hill [57]. Presences of well-developed triangular facets are a signature of a fresh fault scarp. Therefore, the presence of triangular facets is believed to be indicators of neotectonics. Triangular facets have been noticed at a no. of places (Fig. 6a) both in Gola and Kalsa River valley respectively.

Fig. 6.
figure 6

Field photographs showing the presence of (a) triangular facets on the right bank of Kalsa River near Chanphi, (b) asymmetrical terraces present at the left bank of the Gola River near Khansyun, (c) landslide near Khansyun, (d) V-shaped valleys and river meandering near Ranibagh, (e) deep gorges in Kalsa River channel near Chanphi, (f) folds in the gneisses near Paharpani.

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Asymmetrical River Terraces

Formal valley flow and flood plain in any valley represent bench or step-like structure which are known as river terraces [26, 57]. Paired terraces (symmetrical) occur at times of elevation or when down cutting is greater than lateral erosion [26], whereas the unpaired terraces (asymmetrical) formed when lateral erosion dominates. Gola river valley usually formed when lateral erosion dominates. The presence of both paired and unpaired terraces in the study area suggesting that the rate of incision dominates the lateral migration along with the higher rate of uplift. Four levels of asymmetrical terraces (T0, T1, T2 and T3) made up of earlier fluvial deposits rise above the present-day river channel are noticed in the Gola River near Khansyun (Fig. 6b) suggesting that the rates of movement on the two sides of river valley were not uniform.

(1) Landslides. The area is prone to the mass wasting and geomorphologically expressed by the presence of numerous recent landslide deposits all along the valley. These landslides show the geomorphic expression of instability and most of them have been found to be structurally controlled. Huge landslide (Fig. 6c) is witnessed near Khansyun.

(2) V-shaped valleys and river meandering and gorges. Meandering channels (Fig. 6d) develop where bank erodibility is low but flow and load are moderate. The area is characterized by steep slopes deep gorges and V‑shaped valleys forming deep gorges. Deep cut V‑shaped valleys (Figs. 6d, 6e) associated with the tectonic upliftment results in actively incising meander [26]. Contour map of the area (Fig. 7) reveals that the northern part of the study area is more elevated than the southern part. North‒East part of Gola basin is highly elevated (more than 2100 m) than the South‒West part (up to 400 m). The northern part of Kalsa basin is much elevated (more than 2300 m) while the southern part of the basin has maximum elevation up to 1100 m.

Fig. 7.
figure 7

Contour map of Gola and Kalsa River basins, Kumaun Lesser Himalaya, Uttarakhand.

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The slope map studies of any region or area especially the hilly terrain are very helpful in the interpretation of the steepness of the elevated terrains. In the present study, area slope varies from the less than 10 degrees to maximum 71 degrees. According to the slope map (Fig. 8), the study area broadly may be divided into three parts in which southern region having lowest slope in degrees whereas northern part reveals intermediate slopes with the central region having the maximum slopes.

Fig. 8.
figure 8

Slope map of Gola and Kalsa River basins, Kumaun Lesser Himalaya, Uttarakhand.

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RESULTS AND DISCUSSION

Morphometric analysis offers a basis to recognize variation in rock resistance, structural control and priority assessment in a drainage basin. The thorough investigations of the drainage pattern and the evaluation of linear, areal and shape aspects have clearly revealed that the drainage characteristics are noticeably different for each lithology type. Moreover, the climate, rainfall, lithology, topography and slope of the area also control the drainage development [5, 36].

The overall drainage pattern of the Gola and Kalsa River basin is dendritic to sub-dendritic. The unusual appearance of drainage network at many places has given hint to the presence of subsurface structures supported by geomorphic indices. The Gola and Kalsa River basin are the sixth and fifth order streams respectively. The mean stream length ratio (Rl) of the Gola and Kalsa River basins are 0.67 and 0.68 respectively. Rl between streams of different order reveals that the Rl for sub-basins ranges between 0.33–2.81 (Gola River basin) and 0.25 and 1.50 (Kalsa River basin) respectively. The high Rl values as 2.81 and 1.16 for sub-basin nos. 1 and 38 respectively (Gola River) and 1.26 and 1.50 for sub-basin nos. 1 and 12 (Kalsa River) respectively along with high Rb values 5.17 and 7.50 for sub-basin nos. 36 and 40 respectively (Gola River) and 7.00 and 6.75 for sub-basins 7 and 8 respectively (for Kalsa River); indicate towards the dominance of structural control and high tectonic activity in the study area [5, 64]. Higher values of Rb for the sub-basins 39 and 40 (Gola River) is attributed with the presence of HFT in this region. The low values of stream length ratio (Rl) for sub-basins 3 and 36 (Gola River) and for sub-basins 2, 3 and 21 (Kalsa River) and low values of bifurcation ratio (Rb) for sub-basins 7 and 24 (Gola River) and for sub-basins 4 and 18 (Kalsa River) indicate comparative stability in the area. The variation between Rl of the streams of different orders also may be due to the variation in slope and topography of the area. RHO coefficient determines the relationship between the drainage density and the physiographic development of the basin and allows the evaluation of the storage capacity of the drainage network [23]. The maximum value of RHO Coefficient for Gola River Basin is 0.99 (sub-basin 1) and 0.56 (sub-basin 1) for Kalsa River basin. Further minimum values of RHO Coefficient are calculated as 0.06 (sub-basins 36, 40) for Gola River and 0.05 (sub-basin 3) for Kalsa River. Higher values of RHO coefficients of sub-basins indicate its higher water storage capacity during floods and as such reduce the erosion effect during elevated discharge [9, 34].

The stream frequency (Fs) values for Gola and Kalsa River basins are 5.15 and 4.64 km–2. The presence of higher Fs values for the sub-basins in the study area are indicative of relatively higher relief and lower infiltration capacity of the bedrock. The values of mean drainage density (Dd) of the Gola and Kalsa River basins are 3.16 and 3.09 km–1 respectively which shows coarse drainage density in the area and suggests less runoff and more percolation in the area due to the presence of incompetent and permeable lithology with different geological structures [23]. For Gola River basin the sub-basin 37 (coarse texture), 34 (moderate texture) and all other sub-basin show very fine texture. The sub-basins 16 and 23 show fine drainage texture and sub-basins 34, and 37 show coarse drainage texture because of incompetent or highly permeable lithology and low relief. While for Kalsa River basin, sub-basin 20 (moderate texture), 21 (Fine texture) and other show very fine texture.

The total sub-basins of the Gola and Kalsa River were considered for the calculation of Af falling mountainous terrain and alluvium. As the existence of structure in any area plays an important role in the birth of drainage basin asymmetry [20]. The outcome of Af factor demonstrates that the sub-basins (for Gola-5, 26, 39) are showing more tilt as compared to the other part of the area and are having the concentration of geomorphological structures in and around them. HORTON [23] expressed form factor (Rf) as a ratio between the area of the basin (A) and the square of the drainage basin length (L2) which defines the shape of the drainage basin. The value of form factor should be less than 0.7854 (for a perfectly circular basin). Smaller the value of form factor, more elongated will be the basin. The Rf values for the entire Gola and Kalsa River basins are 0.35 and 0.35 respectively that show elongated basins shapes.

Most of the lineaments trends NE‒SW along with few NNE‒SSW and NW‒SE. The intensity and clustering of other similar and less extensive linear trends are suggestive of increased tectonic activity. Based on field observations, some of these lineaments can be categorized as to be of active nature.

The distribution of the contour lines in the study area shows how the surface topography changes in the area. Contour map of the area reveals that the northern part of the study area is more elevated than the southern part. The north-eastern part of Gola basin is highly elevated (more than 2100 m) than the southwestern part (up to 400 m high). The northern part of Kalsa basin is much elevated (more than 2300 m) while the southern part of the basin has maximum elevation up to 1100 m. In the present study, area slope varies from the less than 10 degrees to maximum 71 degrees. Slope map of the study area reveals that the slope in the southern part of the area is gentle whereas northern part reveals intermediate slopes and steep slopes in the central region (Fig. 8).

CONCLUSIONS

The morphometric and quantitative evaluation of the various parameters (namely, linear, aerial, and shape aspects) have been carried out to understand the structural control, neotectonics and active-tectonic activity in the area in the Gola and Kalsa River basins.

The overall drainage pattern of the Gola and Kalsa River basin is found to be dendritic to sub- dendritic. The high stream length ratio (Rl) and bifurcation ratio (Rb) values for various sub-basins of Gola and Kalsa River indicate towards the dominance of structural control and high tectonic activity in the study area. The values of mean drainage density (Dd) of the Gola and Kalsa River basins show coarse drainage density with less runoff and more percolation due to the presence of incompetent and permeable lithology. The outcome of asymmetric factor (Af) demonstrates that the sub-basins for Gola (5, 26, and 39 in Table 3) are showing more tilt as compared to the other part of the area due to which there is a concentration of geomorphological structures in and around them. The form factor (Rf) values for the entire Gola and Kalsa River basins are revealing the elongated basins shapes. General lineaments trend in the area is NE‒SW along with few NNE‒SSW and NW‒SE. Their intensity and clustering pattern is suggestive of increased tectonic activity in which few of them can be categorized as to be of active nature.

The studies carried out on the morphometry and geomorphology of the study area reveals that the drainage pattern and erosion is controlled by climate, rock type and structural fabric of rock, associated with the rapid uplift and intense fluvial incision. The presence of various geomorphic features of active tectonics as well as the anomaly in various drainage parameters of the area indicates a strong structural and tectonic control over the geomorphic evolution of the area.