Dendritic Drainage, Braided Channels and Self-Similarity
September 10, 2010
This pair of images shows remarkably similar dendritic drainage systems and braided main channels, but at vastly different scales. The term "dendritic" is applied to stream networks that branch in a tree-like fashion. Dendritic drainage patterns tend to develop on surfaces that erode uniformly on gentle to moderate slopes. Braided channels, on the other hand, form in streams that carry such heavy sediment loads that they repeatedly clog their active channels, forming new collateral channels on their floodplains. The upper image is a Digital Globe satellite view, courtesy of Google Earth, showing a portion of a dry stream channel in a southern Nevada desert. Note that the linear features in the left-hand portion of the image are roadways. The lower image is a photograph of a tiny dry stream channel at Goblin Valley State Park in Utah. The main channel in the satellite image is nearly 1,500 feet (455 m) wide at its widest point while the main channel in the Goblin Valley photograph has a maximum width of about nine inches (23 cm). The U.S. 25 cent coin in the upper left of the channel provides scale. Landscape features that show self-similarity of form at different magnification scales are termed "fractal." Such self-similarity is common in nature and is exhibited by systems as diverse as stream networks, mountain ranges, coastlines, and snowflakes. Images acquired on January 25, 2010.
Photo details: Bottom - Camera Maker: SONY; Camera Model: DSLR-A100; Focal Length: 28.0mm (35mm equivalent: 42mm); Aperture: f/6.3; Exposure Time: 0.013 s (1/80); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Light Source: Unknown; Flash Fired: No (Auto); Color Space: sRGB.