Abstract
The plan-form structure of the world’s river basins contains extensive information regarding tectonic, paleo-geographic and paleo-climate conditions, but interpretation of this structure is complicated by the need to disentangle these processes from the autogenic behavior of fluvial processes. One method of interpreting this structure is by integrating channel length and drainage area as characterized by the scaling relationship between slope and area, resulting in a characteristic length parameter, referred to in recent studies as χ. In this paper, we apply this methodology at a continental scale by calculating χ for the world’s river networks. Mapping of χ', a modified version of χ including the influence of precipitation distribution on river discharge and correction of base level for χ' in closed basins, illustrates the geometric structure of global river networks, thus highlighting where tectonics or changing climate have resulted in an apparent disequilibrium of the river channel geometry. Our global χ maps quantify a dynamic view of Earth’s river networks and help to identify past and ongoing evolution of Earth’s landscape.
Highlights
Background & SummaryLarge-scale river networks, the backbone of most terrestrial landscapes, play an important role in the evolution of continental landmasses, ecosystems and human geography
Given the importance of large drainage systems and their implications for biological evolution, catchment hydrology and geochemical processes, the planform geometry of river networks and their history of evolution have long been a topic of study, using a range of methodologies
Digital Elevation Models (DEMs) are fundamental data for many geoscience applications, and the accuracy and resolution of global elevation data have significantly improved during the last decade (e.g. GEMTED2010, MERIT19)
Summary
Large-scale river networks, the backbone of most terrestrial landscapes, play an important role in the evolution of continental landmasses, ecosystems and human geography. Drainage networks evolve to efficiently remove water and sediment from the landscape, and their spatial pattern and the geometric characteristics of their branching networks reflect the tradeoff between tectonic uplift and deformation and geomorphic processes of erosion, all modulated by climate and rock type. The dynamics of these interactions imply motion of water divides and exchange of drainage area between basins through river capture. For a basin or set of basins with constant, homogeneous uplift rate, rock erodibility and climate, χ and elevation scale linearly, so under these conditions, values of χ on opposite sides of a divide should be equal. The new world maps and seamless dataset allow users to investigate the dynamics of drainage networks, and to better understand and interpret the impact of drainage reorganization on the Earth system
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