Landscape response to progressive tectonic and climatic forcing in NW Borneo: Implications for geological and geomorphic controls on flood hazard

Abstract

Empirical models have simulated the consequences of uplift and orographic-precipitation on the evolution of orogens whereas the effects of these forcings on ridgelines and consequent topography of natural landscapes remain equivocal. Here we demonstrate the feedback of a terrestrial landscape in NW Borneo subject to uplift and precipitation gradient owing to orographic effect, and leading to less-predictable flooding and irreversible damages to life and property. Disequilibrium in a large catchment recording the lowest rainfall rates in Borneo, and adjacent drainage basins as determined through χ, a proxy for steady–state channel elevation, is shown to result in dynamic migration of water divide from the windward-side of the orogen towards the leeward-side to attain equilibrium. Loss of drainage area in the leeward-side reduces erosion rates with progressive shortening resulting in an unstable landscape with tectonic uplift, gravity faults and debris flows. 14C dating of exhumed cut-and-fill terraces reveal a Mid–Pleistocene age, suggesting tectonic events in the trend of exhumation rates (>7 mm a−1) estimated by thermochronology, and confirmed by morphotectonic and sedimentological analyses. Our study suggests that divide migration leads to lowered erosion rates, channel narrowing, and sediment accretion in intermontane basins on the leeward-side ultimately resulting in enhanced flooding.

Tectono‐morphological evolution of the Cauvery, Vaigai, and Thamirabarani River basins: Implications on timing, stratigraphic markers, relative roles of intrinsic and extrinsic factors, and transience of Southern Indian landscape

“…Selected geomorphic indices that characterize drainage basin in terms of the basin's extent, shape, and relief (Horton, 1932(Horton, , 1945Strahler, 1952aStrahler, , 1952bStrahler, , 1957Strahler, , 1964Smith, 1950;Miller, 1953;Schumm, 1956;Chopra, Dhiman, & Sharma, 2005;Kouli, 1953;Kouli, Vallianatos, Soupios, & Alexakis, 2007) and help assess maturity and equilibrium stages Pérez-Peña, Azañón, Booth-Rea, et al, 2009;Nexer et al, 2015), and evaluating the behaviour of the basin caused by tectonic deformation and and/or climatic forcings (Shary, 2006;Esper Angillieri, 2008;Markose & Jayappa, 2011;Horacio, 2014;Mathew, Menier, Siddiqui, Kumar, & Authemayou, 2016;Manoj et al 2016;Menier et al, 2017) are considered for the present study. In addition, the indices such as longitudinal profile, asymmetry factor, hypsometric integral, mountain front sinuosity, river sinuosity, stream length gradient, and shape factor were also utilized in order to understand how the topography responds to the tectonic deformation.…”

“…Then, the landscape tends toward a stable steady-state while passing through a stage of transience (Montgomery & Foufoula-Georgiou, 1993;Willgoose, 1994;Willett, McCoy, Perron, Goren, & Chen, 2014;Giletycz, Loget, Chang, & Mouthereau, 2015). Thus, the continued yet variable rates (Whipple & Tucker, 1999) of interactions between tectonic and climatic forcings (Wobus et al 2006) result in diversity of landscape evolution (Allen, 2005;Bowman, 2019;Menier et al, 2017;Montgomery & Brandon, 2002;Ramkumar, Menier, Mathew, Santosh, & Siddiqui, 2017;Synder, Whipple, Tucker, & Merritts, 2000). Signatures of disequilibrium and transience can be observed in the geomorphic characteristics, including morphometric properties of river networks that drain the surfaces of these landscapes (Willett, Hovius, Brandon, & Fisher, 2006;Burbank & Anderson, 2011).…”

Unraveling the roles of asymmetric uplift, normal faulting and groundwater flow to drainage rearrangement in an emerging karstic landscape

“…If the observed spatial asymmetry of precipitation has only developed recently contrasting χ ′ on both sides of the divide values could indicate that the landscape is not yet equilibrated to the modern gradient in rainfall. In the later case, we should expect contrasts in χ ′ and southward migration of the drainage divide towards the drier side of the island (loss of area for catchment P and O) (Roe et al ., ; Anders et al ., ; Bonnet, ; Goren et al ., ; Menier et al ., ).…”

“…The phenomenology of divide migration is therefore more easily appraised through physical and numerical experiments that explore the influence of external forcings on divide migration. Notably, these studies have modelled the effects of asymmetric precipitation (Roe et al, 2003;Anders et al, 2008;Bonnet, 2009;Goren et al, 2014;Menier et al, 2017), or spatial variations of uplift rate (Shikakura et al, 2012;Cox et al, 2001;Goren et al, 2014). Such theoretical works use of a suite of landscape metrics for detecting and predicting divide migration.…”

Discovery of buried historical structures in the Kaveri–Kollidam interfluve, southern India

“…India, home to a few of the oldest known civilizations is no exception, with the Indus and Saraswati settlements existing along the banks of the Rivers Indus (Giosan et al, ) and Saraswati (Radhakrishna & Merh, ; Tripathi, Bock, Rajamani, & Eisenhauer, ; Valdiya, ). However, the very landforms that supported human activities and sustenance wreaked havoc and forced the settled communities to shift or vanish from the habitat due to the geohazards (Nigam & Chaturvedi, ; Nigam et al, ) such as earthquake, landslide or flooding (Menier et al, ), etc., that buried and or marooned the settlements causing loss of life and infrastructure. Roy and Sethumadhav () and Valdiya () argued that Neo‐morphotectonics in the catchment of the Kaveri River were the reasons for burial of man‐made infrastructure, whereas, Kale, Achyuthan, Jaiswal, and Sengupta () reported affirmative evidence for catastrophic flooding in the Upper Kaveri River.…”