Central India’s Upper Ken Basin, where the ancient Bundelkhand Craton meets the younger Vindhyan sedimentary rocks, appears at first glance to be a quiet and time-worn landscape. But new research reveals that the region is still being actively shaped by deep, hidden tectonic forces. In a recent study, geographers Kundan Parmar and Satheesh Chothodi used high-resolution elevation data and underground gravity measurements to decode the subtle fingerprints of active deformation imprinted onto the basin’s rivers and valleys.
Their findings, published in the journal Geomorphology and based on a paper available at Science Direct, show that ancient faults, modern uplift and slow tilting continue to steer the paths of the Ken, Sonar and Bearma Rivers, creating steep drops, shifting channels and asymmetric basins. This research, also highlighted on the website of the South Asia Network on Dams, Rivers and People, challenges the notion of a stable peninsula and has significant implications for water resource planning and seismic hazard assessment.
To uncover this story, the researchers mapped 25 sub-basins of the Upper Ken Basin using 30-metre digital elevation data and Bouguer gravity maps from the Geological Survey of India. They applied a suite of morphometric tools—statistical indices that capture the shape and behaviour of river basins—which acted like a detective kit for landscape evolution.
These included the hypsometric integral (which describes how eroded or “young” a landscape is), the stream-length gradient index (used to pinpoint abrupt steepening or knickpoints along river channels), and the Transverse Topographic Symmetry Index (which detects whether a basin is tilted in one direction). Together, these metrics revealed how surface forms respond to hidden structures below.
A key insight came from hypsometric analysis. Across the Upper Ken Basin, values varied widely. Some catchments showed high values and convex profiles, pointing to uplifted, resistant blocks that rivers have not yet carved deeply into. Others exhibited very low values and concave profiles, showing mature, eroded landscapes. These patterns were not random; uplifted blocks consistently showed youthful hypsometry, while subsiding blocks exhibited older, eroded signatures. This provides strong evidence that tectonics, not just rock type, controls the basin's topography.
The story grew sharper through analysis of the stream-length (SL) gradient index, which flags knickpoints—sudden drops or rapids often formed where land is being pushed upward. In the Upper Ken, all three major rivers showed pronounced SL spikes.
The most dramatic appeared on the main Ken River about 141 kilometres from its source, where the SL value climbs to nearly 44,000. This unusual spike is associated with a major topographic break and corresponds with the location of well-known waterfalls such as Raneh Falls. Crucially, this steepening aligns with a strong positive Bouguer gravity anomaly, indicating a dense crustal block rising beneath the river.
The Ken River’s two major tributaries—the Sonar and Bearma—also carry strong signs of tectonic activity. On the Sonar River, a very large SL spike appears about 180 km from its source, reaching around 35,000, matching a clear rise in gravity-based measures which indicate a denser block of rock pushing upward from below. This tells us that the river is responding to tectonic uplift, even though the surface rocks here are soft sandstone and quartz.
The Bearma River shows a similar story. In its lower section, the SL Index jumps to values above 22,000, again marking zones of sudden steepening. These spots line up with sharp changes in the residual gravity anomaly, pointing to buried faults or changes in deep rock layers. Statistical tests confirmed that elevation, used as a proxy for tectonic forcing, explains much more of the SL variability than rock type alone. In short, the rivers are responding to crustal uplift, not just cutting through harder rock.
Another indicator of active deformation came from drainage asymmetry. If one side of a basin is rising, rivers tend to shift toward the opposite direction, creating a lopsided layout. The researchers measured this using the Transverse Topographic Symmetry Index (TTSI). Plotting these values showed consistent directional trends. Most western and south-western catchments displayed south-eastward river migration, with an average direction of around 130 degrees, suggesting the entire region is tilting toward the Vindhyan syncline. Overall, the drainage asymmetry lines up with known fault trends, strengthening the case that these structural features are controlling how rivers shift within their valleys.
To tie the whole picture together, the study used Bouguer gravity maps, which reveal density contrasts beneath the surface. The alignment between steep river segments and positive gravity anomalies proved striking. The major knickpoint on the Ken River, for instance, sits directly atop a gravity high. This consistent spatial pairing points to crustal blocks being uplifted by the reactivation of the Son–Narmada North Fault (SNNF), a deep ENE–WSW structure that has experienced multiple phases of movement.
The study interprets the SNNF as being reactivated in an oblique-reverse manner, essentially tilting the entire block so that rivers migrate, steepen, or flatten depending on whether they cross an uplifted or subsiding segment. Gravity highs reveal these buried blocks even when fault traces are not visible at the surface.
When all the evidence is combined, a coherent picture emerges: the Upper Ken Basin is the site of ongoing neo-tectonic activity, not a relic of ancient processes frozen in time. The rivers lean south-eastward because the land is being subtly tilted in that direction.
Steep knickpoints form where rivers cross rising crustal blocks. Hypsometric differences map out uplifted versus eroded zones. And gravity anomalies trace the hidden architecture of dense blocks and possible blind faults. Together, these signs show that the Son–Narmada lineament remains an active player in shaping this central Indian landscape.
Beyond the scientific implications, the findings have important practical consequences. If rivers in the Upper Ken Basin are adjusting to ongoing uplift and tilting, water-resource planning must account for shifting channels, variable sediment loads and the possibility of long-term river migration. Dams or other infrastructure built along active or tilting blocks may face unanticipated stress, increased erosion, or rapid siltation. The reactivation of deep faults also raises questions about regional seismic hazards, particularly in areas once assumed to be geologically stable.
Parmar and Chothodi’s study highlights how even subtle geomorphic changes can reveal the deeper forces at work beneath a landscape. By using accessible morphometric tools and pairing them with gravity data, the researchers show that the rivers of the Upper Ken Basin still carry the imprint of hidden tectonic movements. Their work adds to a growing understanding that intraplate regions, including parts of central India, remain tectonically dynamic.
For planners, policymakers, and communities in the region, recognizing this evolving landscape will be key to preparing for a future shaped not only by rivers but by the deep Earth forces that guide their paths.
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*Freelance writer
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