Abstract
Okavango delta is a typical distributive fluvial system, which is composed of a series of sand island-river-swamp networks. River migration in the Okavango delta is analyzed by using satellite images from Google Earth and Alaska Satellite Facility (ASF). Four configuration characterization parameters are selected to depict and measure the meandering river. These four parameters are sinuosity index (S), curvature (C), the difference of along-current deflection angle (Δθ) and expansion coefficient (Km). In the fan, the channel migration is mainly asymmetric. According to geomorphic elements and associated features, Okavango Delta can be subdivided into three zones: axial zone, median zone and distal zone. Under the influence of slope, climate and vegetation, different migration modes are developed in different zones. As the river moves downstream, the sinuosity index of the river on the Okavango Delta decreases downstream. Based on the characteristics of different zones, the sedimentary facies model of a single source distributive fluvial system of a meandering river is proposed. The models of channel migration and sedimentary facies have wide application. This research will not only provide a basis for the prediction of future river channels but will also provide important theoretical guidance for the study of the sedimentary morphology of underground reservoirs.
Highlights
With the continuous progress of geomorphology and remote sensing, we can observe the morphology and distribution of a sedimentary system from a macro perspective
Many authors identified the different river migration and meandering loop modes [9,10,11], and Weissmann et al [12] used Google Earth to analyze 724 modern sedimentary basins around the world, defined the distributive fluvial system and concluded that most basins were created via distributive river deposits
The axis of the meander belt (AXmb) is the connecting line for the adjacent bend inflections, which represents the flow direction of the river; its length is equal to length of a single meander loop (Lml), expressed by |AXmb|
Summary
With the continuous progress of geomorphology and remote sensing, we can observe the morphology and distribution of a sedimentary system from a macro perspective. The interdisciplinary integration in the fields of geomorphology and fluvial sedimentology can systematically and quantitatively study the characteristics of a distributive fluvial system (DFS) from provenance to sedimentary basins. This method has provided valuable insight into in-depth studies of modern channels and the evolution of paleochannels and goes deep into the field of oil and gas exploration. The migration law of macro meandering rivers provide insight into the configuration evolution of ancient channels [15,16,17,18,19,20,21], and is important in the prediction of modern rivers. The migration characteristics of different fluvial zones provide a basis for predicting the hydrodynamic characteristics in DFS, which is the reflection of the ongoing research
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