A synergistic approach to morphotectonic evolution for watershed management in the Bearma River Basin, Central India

Tectonic activities have occurred on the Earth's surface for millions of years, and the Earth adjusts accordingly (Williams 2017; Radaideh & Mosar 2019). Rivers are the easiest geomorphological features to show the effects of these tectonic activities due to their rapid morphological changes (Keller & Pinter 2002; Perucca et al. 2014). Morphotectonic analysis helps us better understand the landform evolution and behaviour (Prakash et al. 2016a; Urbano et al. 2017).

As Earth's temperature has risen by 2°C in recent decades, unpredictable climate extremes, including droughts, deserts, and floods, must be anticipated and regulated (UNODRR GAR special report on drought 2021). Apart from unpredicted precipitation, soil degradation is a major concern in India, with 146.8 million hectares of degraded land out of 329 million. A severe drought that lasted for a long time across Asia between 1999 and 2000 impacted almost 60 million people (Dinpashoh et al. 2022). Global environmental disasters have prompted river morphology investigations. The topography of the region can impact the rate and magnitude of the disaster (Dinpashoh et al. 2019). The tectonic-geomorphology of a landscape encompasses the interplay between tectonic processes and climate-driven gradation on a regional scale (Hack 1973; Jaiswara et al. 2019).

The Indian subcontinent's morphology continuously modifies due to constant tectonic activity (Roy & Purohit 2018). Since the Precambrian, the central Indian peninsula has experienced tectonic reactivation (Kothayari & Rastogi 2013). The Son Valley of the Vindhyan Basin appears to have been tectonically disturbed throughout its sedimentation history, possibly up to the present (Baruah & Misra 2013). The Yamuna River and its tributaries shape the architecture of the Gangetic peripheral bulge (Gosh et al. 2017). Rivers draining peninsular India fill the Indo-Gangetic basin at a rate of 0.007 mm/year through erosion (Valdiya 2015).

Several geomorphic indicators have been investigated worldwide to analyse the overprinting of active tectonic deformation on landscape morphology (Strahler 1964; Hack 1973; Blanc et al. 2020). Similar approaches are also adopted in various geological settings in the Indian subcontinent (Joshi et al. 2013; Kale et al. 2013; Prakash et al. 2019). The morphological and structural setup of northern peninsular rivers has been investigated to understand the erosional and depositional dynamics in the Ganga basin, which helps to deal with natural disasters in the nation's most populated region (Valdiya 2015; Bhatt et al. 2021). Some work has already been done on northern peninsular rivers related to drought risk, geochemistry, and morphometry (Jain et al. 2015; Panda et al. 2019; Singh et al. 2022). However, very limited work has been carried out on the morphotectonic perspective of these rivers. The Bearma River Basin (BRB) requires extensive study as it is one of the most prominent tributaries of the Gangatic marginal river systems in the drought-prone Bundelkhand region. Various geospatial techniques have provided effective ways to study any region's morphotectonic characteristics, which were conventionally thought to be undisturbed (Peshwa et al. 1987).

The present study of the BRB aims at: (1) morphotectonic analysis to comprehend the tectonics' effect on the drainage network and landscape; (2) topographical (slope length and steepness factor) characterization, lineaments, and drainage orientation analysis to understand hydrological behaviour; and (3) tectonic activity categorization using the analytical hierarchy process (AHP) technique to demarcate the tectonically active zone. This assessment would provide a better understanding of the northern peninsular river's evolution and be helpful in watershed management in such a drought-prone area of Central India.

The BRB is present in the Son Valley region of the Vindhyan basin. The Bearma River flows through Deccan Traps, Lameta Limestone, Rewa Sandstone, Lower Bhander Sandstone, Bhander Limestone, Lower Bhander Shale, Upper Bhander Sandstone, Ken Alluvium, and small Laterite outcrops (Figure 1(a)–1(c)). Upper Bhander Sandstone covers 70% area of the BRB (Figure 1(d)).

Tectonic activity has frequently disrupted sedimentation in the Son Valley, and it has persisted to the present day. The Jabera depression has remained tectonically more active than the Damoh depression over time (Baruah & Misra 2013). The Narmada Son North Fault (NSNF), with an ENE-WSW trend, surrounds the southern and south-eastern parts of the BRB. The NSNF is a prominent linear tectonically active feature in central India. It contributes significantly to sediment deposition and the development of folded structures in the Vindhyan formations (Kaila et al. 1989). Several faults divide the Vindhyan basin into small, elongated basins tilted northward (Valdiya 2015). The Vindhyan basin is an extensive regional syncline trending ENE-WSW (Ramasamy & Bakliwal 1988). The Asmara fault, which separates the Bundelkhand granite massif from Bijawar and Vindhyan rocks, encircles the northern portion of the Vindhyan syncline (Krishnamurty & Srivastava 1980). A mosaic of lineaments has been identified in the Deccan volcanic province, which are the expressions of the rejuvenation of Precambrian basement faults (NE–SW); thus, fractures show parallelism with basement trends (Peshwa et al. 1987).

This study examined the BRB's tectonic imprint using 11 morphotectonic parameters (Table 1), lineament density (LD) and slope length and steepness factor (LS) analysis (Figure 2). Morphotectonic analysis of a drainage network begins with Strahler (1956) hierarchical stream ordering method. The formula for calculation and value ranges with the significance of morphotectonic parameters, LD and LS have been described in Table 1.

Table 1

Morphotectonic parameters, slope length and steepness factor and lineament density with formula and references, value and validity ranges, and respective remarks on their significance in terms of tectonic activity

.	Morphotectonic parameter .	Formulation .	Values/validity range .	Remark .
1	Basin relief (R)	⁠; Emin = minimum elevation, Emax = maximum elevation (Schumm 1956)	High values: in hilly terrain, moderate values: in plateau-plain topography, and low value: in the plain areas (Schumm 1956)	The high R-value reflects the geomorphologically young or uplifted terrains with steeper valley and stream bed slopes, and high erosion, while the low value represents the old geomorphic development stage (Schumm 1956; Ghasemlounia & Utlu 2021)
2	Bifurcation ratio (Rb)	⁠; Nu = stream number of u order, Nu − 1 = stream number of next higher order (Horton 1945)	Rb ranges from 2 in flat or gently sloped terrain, 4 or 5 in highly dissected or mountainous topography (Horton 1945)	Rb is higher in the hard rock basement and tectonically unstable regions (Horton 1945)
3	Elongation ratio (Re)	⁠; π = 3.14, Lb = Basin length, A, area of the basin (Schumm 1956)	Re > 0.9 present in a circular basin, 0.9–0.8 oval, 0.8–0.7 less elongated, <0.7 elongated (Chandrakant & Shaikh 2019)	The elongated basin represents tectonic activity with prominent headward erosion, and the circular basin represents a tectonically inactive and geomorphologically mature basin.
4	Hypsometric Integral (Hi)	⁠; Emean, Emin, and Emax represent the mean, minimum, and maximum elevation (Strahler 1952)	Hi < 0.4 in old geomorphic development stage; mature stage Hi = 0.4 to 0.5; youthful stage- Hi > 0.5	The old landscape reflects low relief, minimum erosion, and tectonically inactive region; moderate relief and erosion characterize the mature landscape; early or youthful landscape reveals the presence of high relief with prominent erosion. The young landscape is also found in rejuvenated or tectonically uplifted terrain (Chen et al. 2003; Prakash et al. 2016b).
5	Asymmetry factor (Af)	;Art = area of the right side of the basin, At0tal = total area of the basin (Hare & Gardner 1985)	Af = 50 in a symmetrical basin, Af ≠ 50 in the asymmetrical basin (Hare & Gardner 1985)	The Af values above or below 50 imply lithological control or active tectonic processes, which lead to river migration towards the basin's left or right margin. The symmetrical basin suggests no tectonic activity (Radaideh & Mosar 2019; Bhat et al. 2020).
6	Transverse topographic symmetric factor (T)	;Da = distance from the trunk stream to the midline of its drainage basin, and Dd = distance from the drainage divide to the basin midline (Cox 1994)	T = 0, symmetrical basin T = 1, asymmetrical basin (Cox 1994)	The symmetrical basin reflects the tectonic inactivity, while the basin's asymmetry shows the tilting direction, leading to the trunk channel's migration toward the tilting or away from upliftment (Bhat et al. 2020).
7	Ruggedness number (Rn)	⁠; Dd = Drainage density of the basin (Costa 1987)	Rn < 0.1 value represents the minimal or smooth topography, 0.1–0.4 for mild, 0.4–0.7 for moderate, 0.7–1.0 sharp, and >1.0 high topography (Farhan et al. 2015)	The high Rn value indicates extensive soil erosion and a structurally complex region with tectonic deformations, while the low value inferred a tectonically stable area with little erosion (Prakash et al. 2016c).
8	Sinuosity index (Si)	;C = channel length; V = straight-line valley length (Gomez & Marron 1991)	Si ≤ 1 represents straight course; Si = 1.0–1.5, sinuous course; Si > 1.5, meandering path (Muller 1968)	High Si values indicate inactive terrain, whereas low Si values indicate active mountain fronts (Baruah et al. 2020).
9	Mountain front sinuosity (Smf)	;Lmf = the mountain front length, and Ls is the straight-line length of the same front (Bull & McFadden 1977)	Smf = 1.0–1.6 for active mountain fronts, 1.8–3.4 = moderately active fronts, 2.0–7.0 = inactive fronts (Bull & McFadden 1977)	Higher Smf indicates inactive mountain fronts, while lower Smf depicts active mountain fronts (Bhat et al. 2020).
10	Stream length-gradient Index (SL)	; ΔH = elevation difference of that particular reach, ΔL = length of the segment, L = total length of the channel from the midpoint of that particular segment to the drainage divide from upstream (Hack 1973)	Streams flowing over active uplifts have a greater SL, whereas a lower SL indicates soft and low-resistance subsurface material (El Hamdouni et al. 2008).	An abnormal SL value indicates the presence of a knick point or a break zone along the longitudinal profile of the river. When a knick point lies at the junction of two opposing lithologies, it is lithologically generated. In contrast, when a knick point lies within a particular lithology, it is tectonically generated and controlled (Bhat et al. 2020).
11	Valley floor width and height ratio (Vf)	;Vfw = width of valley floor, Eld = elevation of the left side valley divide, Erd = elevation of the right side valley divide, Esc = elevation of river valley floor (Bull & McFadden 1977)	VF > 1 represents a U-shaped valley with significant lateral erosion; VF < 1, a V-shaped valley with active headward erosion (Bull & McFadden 1977)	A U-shaped valley is characterized by lateral erosion, whereas a V-shaped valley is characterized by active headward erosion. In tectonically uplifted regions with prominent erosional slopes, there is also active headward erosion, resulting in incised V-shaped valleys (Bull & McFadden 1977).
12	Lineament density (LD)	Number of lineament per unit area	High lineament density reveals high tectonic deformation (Nur 1982; Prakash et al. 2016c)	Lineament density reveals the intensity of deformation (Singh et al. 2021)
13	Slope length and slope steepness factor (LS)	;; FA is flow accumulation and CS is the cell size, ; L is slope length factor, θ is slope in degree (Moore et al. 1991)	A high LS value is present in the active basin, while a low LS value is present in an inactive basin (Ganasri & Ramesh 2016)	The LS has a significant impact on erosion, which indicates how erosion is dynamically affected by the basin's activities (Gansri & Ramesh 2016). With an increase in slope length, soil loss per unit area also increases. On steeper slopes, erosion is more severe (Getu et al. 2022).

.	Morphotectonic parameter .	Formulation .	Values/validity range .	Remark .
1	Basin relief (R)	⁠; Emin = minimum elevation, Emax = maximum elevation (Schumm 1956)	High values: in hilly terrain, moderate values: in plateau-plain topography, and low value: in the plain areas (Schumm 1956)	The high R-value reflects the geomorphologically young or uplifted terrains with steeper valley and stream bed slopes, and high erosion, while the low value represents the old geomorphic development stage (Schumm 1956; Ghasemlounia & Utlu 2021)
2	Bifurcation ratio (Rb)	⁠; Nu = stream number of u order, Nu − 1 = stream number of next higher order (Horton 1945)	Rb ranges from 2 in flat or gently sloped terrain, 4 or 5 in highly dissected or mountainous topography (Horton 1945)	Rb is higher in the hard rock basement and tectonically unstable regions (Horton 1945)
3	Elongation ratio (Re)	⁠; π = 3.14, Lb = Basin length, A, area of the basin (Schumm 1956)	Re > 0.9 present in a circular basin, 0.9–0.8 oval, 0.8–0.7 less elongated, <0.7 elongated (Chandrakant & Shaikh 2019)	The elongated basin represents tectonic activity with prominent headward erosion, and the circular basin represents a tectonically inactive and geomorphologically mature basin.
4	Hypsometric Integral (Hi)	⁠; Emean, Emin, and Emax represent the mean, minimum, and maximum elevation (Strahler 1952)	Hi < 0.4 in old geomorphic development stage; mature stage Hi = 0.4 to 0.5; youthful stage- Hi > 0.5	The old landscape reflects low relief, minimum erosion, and tectonically inactive region; moderate relief and erosion characterize the mature landscape; early or youthful landscape reveals the presence of high relief with prominent erosion. The young landscape is also found in rejuvenated or tectonically uplifted terrain (Chen et al. 2003; Prakash et al. 2016b).
5	Asymmetry factor (Af)	;Art = area of the right side of the basin, At0tal = total area of the basin (Hare & Gardner 1985)	Af = 50 in a symmetrical basin, Af ≠ 50 in the asymmetrical basin (Hare & Gardner 1985)	The Af values above or below 50 imply lithological control or active tectonic processes, which lead to river migration towards the basin's left or right margin. The symmetrical basin suggests no tectonic activity (Radaideh & Mosar 2019; Bhat et al. 2020).
6	Transverse topographic symmetric factor (T)	;Da = distance from the trunk stream to the midline of its drainage basin, and Dd = distance from the drainage divide to the basin midline (Cox 1994)	T = 0, symmetrical basin T = 1, asymmetrical basin (Cox 1994)	The symmetrical basin reflects the tectonic inactivity, while the basin's asymmetry shows the tilting direction, leading to the trunk channel's migration toward the tilting or away from upliftment (Bhat et al. 2020).
7	Ruggedness number (Rn)	⁠; Dd = Drainage density of the basin (Costa 1987)	Rn < 0.1 value represents the minimal or smooth topography, 0.1–0.4 for mild, 0.4–0.7 for moderate, 0.7–1.0 sharp, and >1.0 high topography (Farhan et al. 2015)	The high Rn value indicates extensive soil erosion and a structurally complex region with tectonic deformations, while the low value inferred a tectonically stable area with little erosion (Prakash et al. 2016c).
8	Sinuosity index (Si)	;C = channel length; V = straight-line valley length (Gomez & Marron 1991)	Si ≤ 1 represents straight course; Si = 1.0–1.5, sinuous course; Si > 1.5, meandering path (Muller 1968)	High Si values indicate inactive terrain, whereas low Si values indicate active mountain fronts (Baruah et al. 2020).
9	Mountain front sinuosity (Smf)	;Lmf = the mountain front length, and Ls is the straight-line length of the same front (Bull & McFadden 1977)	Smf = 1.0–1.6 for active mountain fronts, 1.8–3.4 = moderately active fronts, 2.0–7.0 = inactive fronts (Bull & McFadden 1977)	Higher Smf indicates inactive mountain fronts, while lower Smf depicts active mountain fronts (Bhat et al. 2020).
10	Stream length-gradient Index (SL)	; ΔH = elevation difference of that particular reach, ΔL = length of the segment, L = total length of the channel from the midpoint of that particular segment to the drainage divide from upstream (Hack 1973)	Streams flowing over active uplifts have a greater SL, whereas a lower SL indicates soft and low-resistance subsurface material (El Hamdouni et al. 2008).	An abnormal SL value indicates the presence of a knick point or a break zone along the longitudinal profile of the river. When a knick point lies at the junction of two opposing lithologies, it is lithologically generated. In contrast, when a knick point lies within a particular lithology, it is tectonically generated and controlled (Bhat et al. 2020).
11	Valley floor width and height ratio (Vf)	;Vfw = width of valley floor, Eld = elevation of the left side valley divide, Erd = elevation of the right side valley divide, Esc = elevation of river valley floor (Bull & McFadden 1977)	VF > 1 represents a U-shaped valley with significant lateral erosion; VF < 1, a V-shaped valley with active headward erosion (Bull & McFadden 1977)	A U-shaped valley is characterized by lateral erosion, whereas a V-shaped valley is characterized by active headward erosion. In tectonically uplifted regions with prominent erosional slopes, there is also active headward erosion, resulting in incised V-shaped valleys (Bull & McFadden 1977).
12	Lineament density (LD)	Number of lineament per unit area	High lineament density reveals high tectonic deformation (Nur 1982; Prakash et al. 2016c)	Lineament density reveals the intensity of deformation (Singh et al. 2021)
13	Slope length and slope steepness factor (LS)	;; FA is flow accumulation and CS is the cell size, ; L is slope length factor, θ is slope in degree (Moore et al. 1991)	A high LS value is present in the active basin, while a low LS value is present in an inactive basin (Ganasri & Ramesh 2016)	The LS has a significant impact on erosion, which indicates how erosion is dynamically affected by the basin's activities (Gansri & Ramesh 2016). With an increase in slope length, soil loss per unit area also increases. On steeper slopes, erosion is more severe (Getu et al. 2022).

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Relative tectonic activity may be assessed using an array of geomorphic indicators. Active tectonic indicators may identify irregularities or anomalies in the river system. Local tectonic activity resulting from subsidence or uplift may have caused these anomalies. However, it is challenging to determine the rates of active tectonics or to find out the specific area for quantitative investigations to determine the relative rates of tectonic deformations (El Hamdouni et al. 2008). Few researchers have attempted to extract the relative tectonic activity by combining two to three morphotectonic indicators to give semi-quantitative data on the relative tectonic activity. Bull & McFadden (1977), Silva et al. (2003), and El Hamdouni et al. (2008) have attempted a semi-quantitative sub-basins categorization into different classes according to some morphotectonic parameters (mountain front activity and valley floor width and height ratio) to extract the relative tectonic activity. Das (2021) performed the bivariate inter-correlation matrix analysis to determine the relationship among the morphometric variables in Peninsular India.

All 13 × 13 matrix values are significant at the 0.029 consistency level. The weightage of each parameter is based on experts' judgments, according to the nature of the selected landscape and conclusions made from various previous literatures. In the present study, the SL index is considered the most important factor, while the V_f is the least important factor. The SL index analyses the slope break in the longitudinal profile and thus helps to examine the cause of the slope break (tectonic or lithological). The majority of drainage valleys are broad and confined in nature, so V_f does not provide as many significant results to demarcate the tectonic activity spatially as the rest of the parameters. The inter-correlation matrix shows the analytical hierarchical correlation among the 13 thematic layers (Table 2). The weighted sum functions of the spatial analyst tool were used to construct the tectonic activity map from the normalized vector of inter-correlation values for each parameter. Interpolation, multiple value extraction, correlation, and integration of all 13 thematic layers generated a tectonic activity map. The detailed version of the table 2 is provided as supplementary material.

Table 2

Inter-correlation matrix among the morphotectonic parameters, lineament density (LD) and slope length and steepness factor (LS) for tectonic activity in the BRB

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For model cross-validation, this research investigates the area under the ROC curve (AUC) as a performance evaluation of the proposed model through an algorithm of machine learning. The ROC (receiver operating characteristic) is a graphical representation of the diagnostic accuracy of binary classifiers (Bradley 1997). The ROC curves show the true-positive rate (TPR) versus the false-positive rate (FPR). The TPR is the proportion of correctly predicted positive observations out of all positive observations. Similarly, FPR is the proportion of all negative observations that are incorrectly predicted to be positive (Jaskowiak et al. 2022). The ROC curve and AUC have been prepared in Arc SDM extension tool of Arc GIS. The calculation is based on the concept that the AUC/ROC matrices are counts of the correct and incorrect classifications from each class that a classification technique has produced during testing by comparing each value to others (Table 3). The AUC/ROC matrix is a correlation table that displays the variations in true and predicted classes for an array of annotated tests. The AUC/ROC matrix displays every possible statistic on the performance of the classifier or model. The AUC is calculated using trapezoidal integration when the decision threshold has been varied, and several points on the ROC curve have been acquired (Bradley 1997) (Table 3).

Table 3

AUC/ROC performance matrices and formulas for model validation

Performance matrices and formulas .
.	Predicted class .			.
True class .	Negative .	Positive .	Outcome .	Reference .
				Bradley (1997), Jaskowiak et al. (2020)
Negative	True negative (T−ve)	False positive (F+ve)	True negative classes (TN)
Positive	False negative (F−ve)	True positive (T+ve)	True positive classes (TP)

Performance matrices and formulas .
.	Predicted class .			.
True class .	Negative .	Positive .	Outcome .	Reference .
				Bradley (1997), Jaskowiak et al. (2020)
Negative	True negative (T−ve)	False positive (F+ve)	True negative classes (TN)
Positive	False negative (F−ve)	True positive (T+ve)	True positive classes (TP)

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In general, the higher the AUC value, the better the model performance under assessment; values of AUC around 0.5 suggest the predicted performance of the model is moderate, while values below 0.5 indicate a worse model performance than expected (Jaskowiak et al. 2020).

The BRB has an undulating plateau-plain shape with a moderately high relief, signifying substantial erosion (Table 4). The high relief of Sun, Bhadar, Jharauli, Guraiya, Bamner, Pathri, Basa, and Bearma sub-basins (SB) represents uplifted terrain with active erosion. Parewa and Karaundi have low relief and comparatively more mature landscapes. Higher relief produces steeper slopes in the valleys and along stream beds, shorter periods of flow accumulation, higher flood peaks, and increased erosion on slopes and valley beds.

The fifth-order stream displays the highest R_b implying greater overland flow and discharge owing to an impervious rock formation associated with a steep slope. High R_b (4.39) of the BRB reflects the dissected topography. Karaundi and Parewa SB have a lower R_b, while Jharauli, Guraiya, Bhadar, Sun, and Bearma SB display a high R_b.

The low R_e identified an elongated shape of the BRB, Bearma, Bamner, and Sun SB, suggesting deformational control. Jharauli SB is circular, while Bhadar, Guraiya, Basa, and Parewa are nearly circular, and Pathri and Karaundi are nearly elongated. The BRB elongated along the NE–SW direction; however, at sub-basin level, the elongation direction is variable. In Pathri, Sun, Bhadar, Guraiya, Jharauli, and Bearma, the main channel does not follow the regional slope, causing basin extension in the NW–SE direction. Elongation occurs in the NE–SW and NW–SE directions in Sun and Bhadar, representing two major deformational directions.

The T values of the BRB and its sub-basins show the asymmetrical basin. Overall dynamics show streams in the lower BRB are shifting towards the SW direction, while streams in the upper BRB undergo lateral shifting towards the NW. Guraiya, Jharauli, Sun, and Bhadar exhibit higher T values, while Parewa, Bamner, Basa, and Bearma SB exhibit lower values. Polar plots show T-vector directions and magnitudes along trunk streams and sixth-order tributaries (Figure 5). Transverse asymmetry, vector direction, and magnitude analysis along different segments indicate Bearma's south-westward tilting. However, the trunk channel exhibits a lateral tilt towards the northwest. Pathri, Jharauli, Sun, Bhadar, and Karaundi have an average southward lateral tilt. Bearma and Bamner have northwest lateral tilts, and Parewa has northeast tilting. Bhadar channel tilts north-westerly upstream and south-westerly downstream.

The R_n (0.63) of the BRB basin displays a moderately rugged topography. The structurally complex and steep terrain of the Bhadar, Sun, Jharuali, Bamner, Guraiya, and Bearma exhibit high R_n. Rigorous fluvial erosion characterizes these sub-basins, creating incised valleys. Karaundi, Pathri, and Parewa display low R_n due to a low gradient and mild morphology. The R_n indicates a sharp morphology in the southern and south-eastern regions of the BRB, indicating the reactivation of structural elements.

As a result of the moderate S_i value (1.24), it was inferred that the drainages followed a sinuous route within the BRB basin. The S_i of sub-basins shows sinuous stream paths except for the Bamner (meandering course). Streams flowing through the southern and south-eastern active mountain fronts develop a straight course with low S_i, while downstream, they develop a more sinuous path and become meandering near the confluence. Streams near the active mountain front in the south and south-eastern regions flow straight and have a low S_i value, while downward streams flow more sinuously and become meandering near the confluence.

The S_mf (1.96) of the BRB reveals the moderately active mountain fronts positioned between several topographic lows. The S_mf of the BRB indicates that active tectonics and fluvial erosion are simultaneously modifying the basin. Sub-basins in the south-eastern portion of the BRB, such as Sun, Bhadar, Guraiya, and Jharauli, show lower S_mf, reflecting tectonically active mountain fronts. The moderate S_mf of Bamner, Pathri, Basa, and Bearma SB indicates a moderately active mountain front, while Parewa and Karaundi, with higher S_mf, indicate a tectonically inactive mountain front.

According to the BRB's V_f value (11.57), the valleys generally appear to be U-shaped. The V-shaped transverse valley profile with the lower V_f of Bhadar, Sun, and Jharauli displays active headward erosion. In contrast, Pathri, Basa, Bearma, Bamner, Parewa, and Karaundi SB have U-shaped valleys with more lateral erosion. Lower V_f in the BRB near moderately active to active mountain fronts corresponds to V-shaped valleys with active incisions. Higher V_f is linked with gentle gradients and moderately to less active portions of the basin. Bearma is a bedrock river with a terrace-confined valley in incised and degraded landscapes with long-term sediment sources or transfer zones. Structural and lithological controls are pervasive and generate valley confinement.

The relative tectonic activity map of the BRB has five tectonic activity classes, from very low to very high (Figure 9(b)). In the BRB, 17.74, 38.22, 20, 13.11, and 10.93% areas have very low, low, moderate, high, and very high tectonic activity. Tectonic activity analysis indicates that the northern and north-western parts of the basin are non-active. The moderate to high tectonic activity present in the southern and southern-eastern parts of the Bearma basin is due to the effect of the NSNF activity. Major deformation occurs either parallel to or perpendicular to the fault.

The ROC- and AUC-based validation for the tectonic activity model of the Bearma basin represents the high accuracy of the model. The AUC greater than 0.8 shows a good performance of the presented model (Figure 9(c)).

The BRB lies in a subtropical region with a semiarid climate characterized by high temperatures and low rainfall throughout the year. Drought is a concerning issue in the region. The Bearma basin is located within the Vindhyan plateau and ranges, with mountain heights ranging from 400 to 752 m AMSL on the southern edge of the basin. The moisture-laden SW monsoon winds (Arabian Sea branch) are orographically affected by the high Vindhyan hills. This creates heavy precipitation on mountain ranges' windward slopes and slightly diverts monsoonal winds. High mountain ranges create a rainfall shadow zone on their leeward side as orographic barriers. Monsoonal cloud moisture and precipitation diminish as they move towards the north. Discontinuous mountain ranges cannot provide a significant rainfall shadow zone. Thus, lithology and tectonic deformations have more control over drainage patterns than climate. Climate and tectonics can act together to regulate the sedimentation nature of the BRB.

Several cross-sections of the Bearma River show three different gravelly channel deposits separated by an erosional contact with angular to sub-rounded clasts and a large amount of matrix. This suggests that the sediment was laid down during a high-energy period. Gravel concentration varies from bottom to top in response to climatic and tectonic changes in the source area over time. High water budgets result from intense climate and tectonic activity, enhancing the river's erosional and transportation capabilities.

The morphotectonic parameters and field data show that the Bearma basin exhibits tectonic control over drainage networks and sedimentation processes in some parts. For drought mitigation strategies, dams and reservoirs are an invaluable component. The stability of the ground is vital for future settlements and town planning, including the construction of roads, buildings, dams, and reservoirs. The Bearma basin falls within the drought-prone Bundelkhand region, which has suffered from several droughts in the past. Deformational structures (foliation, lineation, faults, and joints) form secondary porosity in hard lithological terranes, which create excellent aquifers in some places. In the BRB, the present study can assist the groundwater survey by locating secondary porosity. Similarly, the surrounding area may be investigated to gain a better understanding of the dynamics of the northern peninsula.

Morphotectonic analysis reveals that the BRB has experienced neotectonic activity. The BRB has high relief, high erosion, and deeply incised streams. The southern and south-eastern regions display more activity. The high ruggedness number, low bifurcation ratio, and high stream length-gradient index of Bhadar, Bamner, Jharauli, Guraiya, and Bearma SB indicate the high gradient and erosive nature of the streams. Diverse lithological variations also affect the morphotectonic characteristics of some parts of the basins.

Lineament study of the BRB indicates that the southern and south-eastern portions are more deformed. Due to the tectonic exhumation of the Vindhyan, Deccan trap basement, and Son-Narmada North Fault, there is a significant degree of deformation in the BRB in the NE–SW and NW–SE directions.

Based on the topographic analysis, it is evident that the highly active sub-basins are subject to rigorous erosion. It is estimated that approximately 24.04% of the BRB is experiencing high to very high levels of tectonic activity.

Morphotectonic study, comparative tectonic activity analysis, and lineament analysis analyse the slope failures for future disaster management planning. By locating secondary porosity in the Bearma basin, the present work significantly contributes to the groundwater survey in the drought-prone Bundelkhand region. Bearma Basin's tectonic activity analysis could potentially be used in future infrastructure development programs in a sustainable way in drought-stricken areas. Similar research may use the expert knowledge-based AHP method with adequate performance assessment of the proposed model.

The authors would like to extend their gratitude to the Head of the Department of Geology and IOE Grant (CBP No. 0257) of Banaras Hindu University for providing them with the necessary facilities and workspace. K Prakash expresses appreciation for the financial assistance received through the SERB Grant (No. EEQ 2017 000703). P Singh is thankful to the University Grants Commission for providing financial support in the form of the UGC-SRF fellowship (no. 453) (CSIR-UGC NET DEC. 2016).

All relevant data are available from an online repository or repositories (Advanced Spaceborne Thermal Reflection and Emission Radiometer (ASTER): www.earthdata.nasa.gov); (Landsat (ETM+) data: earthexplorer.usgs.gov); (Lithological data: Bhukosh.gov.gsi.in); (Meteorological data: imdpune.gov.in).

The authors declare there is no conflict.