Tectonics, lithology and climate controls of morphometric parameters of the Edea - Eseka region (SW Cameroon, Central Africa): Implications on equatorial rivers and landforms

Abstract

Shuttle Radar Topography Mission (SRTM) - 3 data for Digital Elevation Model through morphometric analyses of the Sanaga, Nyong and Kelle watersheds and landform were correlated with field survey in a Geographical Information System (GIS) model in the Edea-Eseka Region in SW Cameroon; erected on Paleo-to Neoproterozoic crystallophyllian rock types, Cretaceous to Recent sedimentary formations later affected by reactivated and neotectonic faults. This study that aimed to evaluate the lithology, tectonic and climate interactions on operating processes and landform characteristics based on the morphometric parameters of watersheds. Parameters vary from one watershed to another establishing one to three controls. The density drainage (0.05–0.29), the constant of channel maintenance (3.5–19.47) and the drainage pattern; outlines the lithological, the tectonic and the climate controls of the morphology. The Bifurcation ratio (2–5.25), the mean bifurcation ratio (3.67–4.09), the relative relief ratio (0.21–0.27), the watershed slope (5.75–9.35) and the watershed deviation (105–507); highlights the lithostructural controls of the morphology; whilst the wandering ratio (1.54–2.12) individualises both, the structural and climate controls. The stream number (370–2473) and the stream length ratio (0.57–1.91), the elongation ratio (0.47–0.55), the circularity ratio (0.25–0.29), fitness ratio (0.56–0.63), dissection index (0.91–0.99), the concavity index (−0.1-0.56), the hypsometric integral (0.45–0.49) and the stepped longitudinal length profiles, establishes the dominant tectonic controls of the morphology; while the rho coefficient (0.34–0.43) and drainage texture (1.91–4.75) displays the lithological control of the morphology and; the drainage intensity (1.76–7.62) and the length overland flow (1.75–9.74) typified the climate control of the morphology. The Edea-Eseka Region uplift rejuvenates old watershed each time they evolve to equilibrium because of lithological variations, neotectonics, differential erosion and climate variations; overriding its morphology. This geodynamic and climatic control of morphometric processes in the SW Cameroon can be extended to the whole of Central Africa and in Equatorial Regions that display similar evolutions.