Abstract
Characteristics and spatial variation in geomorphic processes in the Meenachil river basin in southern Western Ghats, Kerala, India, is documented by analyzing the hypsometric parameters of 49 subwatersheds of 5th, 4th and 3rd order. Hypsometric curves and parameters such as hypsometric integral (Ea), maximum concavity (Eh), coordinates (a*, h*) of the curve-slope inflection point (I), normalized heights of the hypsometric curve at 20%, 50% and 80% of the area indicate spatial variation. Longitudinal profile of the river shows a highly disturbed region above, a flow length of 20km and relatively less disturbed area downstream. Hypsometric integral classifies most of the subwatershed into mature and mature to old age transition while varying shapes of the hypsometric curves imply the influence of tectonic uplift. Variation of hypsometric concavity in close spatial proximity also confirms the variation in the effect of tectonic processes in the region, where the combination of fluvial and diffusive process is active and are evident from the high hypsometric head and toe measurements. Repeated occurrences of earthquakes in the region confirm the presence of ongoing tectonic activity, which have direct bearing on the geomorphic characteristics of river basin.DOI: http://dx.doi.org/10.5755/j01.erem.73.4.19553
Highlights
Morphometric analysis, which reveals the river basin characteristics, usually lacks in-depth details of relief characteristics of the basin
In order to characterise the geomorphic evolution of the Meenachil river basin, moderate resolution Shuttle Radar Topographic Mission (SRTM) digital elevation data, available on the USGS website, were downloaded and processed
The characteristic shape of the longitudinal profile nullifies the effect of lithological variation in causing such changes, because the river flows through a single lithology for most of its flow length suggesting a differential effect of the tectonic process in the region
Summary
Morphometric analysis, which reveals the river basin characteristics, usually lacks in-depth details of relief characteristics of the basin. The hypsometric integral (Ea) indicates the percentage volume of the original basin that remains unaltered and shows the trade-off between erosion and tectonics with respect to the base level erosion (Strahler 1952, Kale and Shejwalkar 2008, Ahmad et al 2014) Away from this straightforward approach which uses the hypsometric curve shape and integral to understand and classify the geomorphic evolution stage of the drainage basin, Willgoose et al (1991), Willgoose (1994) and Sinha-Roy (2002) proposed a detailed analysis of hypsometric curve parameters such as hypsometric head, toe, inflection point and concavity. Very few studies have utilised the characteristics of the hypsometric curve to derive holistic information about the geomorphic evolution stage of river basins (Sinha-Roy 2002, Chattopadhyay et al 2006, Markose and Jayappa 2011, Gopinath et al 2014, 2016, Dash et al 2016)
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