Braided river
photo by Unhindered by Talent on Flickr
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- Uploaded:
- Dec 04, 2009
- Original:
- 1620 × 1080
- Original date:
- Jul 23, 2006
Braided rivers are an odd lot, and behave quite differently from the rivers I'm used to dealing with. Being the result primarily of glacial melt, braided rivers are full of silt ("glacial flour"), which they are constantly depositing and picking up again. (You can see the gray areas of water in the picture, which are full of this "flour".) Thus where a "normal" river spends it's life carving out valleys (or even canyons) on it's way down to the sea, braided rivers are in fact filling valleys in, carrying the ground up dust of the mountains down to the valley floor.
Because of this they never keep to a single, well defined channel, because that channel would eventually acquire enough silt to push the river elsewhere. (Not unlike the delta region of a major river like the Mississippi.) Hence their name, as they weave braids all across the valley floor.
Wikipedia Article
Denali National Park and Preserve is located in Interior Alaska and contains Denali (Mount McKinley), the highest mountain in North America.
The national park and preserve is over 6 million acres (24,500 km²), of which 4,724,735.16 acres (19,120 km²) are federally owned. The national preserve is 1,334,200 acres (5,430 km²), of which 1,304,132 acres (5,278 km²) are federally owned. On December 2, 1980, a 2,146,580 acre (8,687 km²) Denali Wilderness was established within the park.
Denali habitat is a mix of forest at the lowest elevations, including deciduous taiga. The preserve is also home to tundra at middle elevations, and glaciers, rock, and snow at the highest elevations. The longest glacier is the Kahiltna Glacier.
Today, the park hosts more than 400,000 visitors who enjoy wildlife viewing, mountaineering, and backpacking. Wintertime recreation includes dog-sledding, cross-country skiing, and snowmachining where allowed.
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A braided river is one of a number of channel types and has a channel that consists of a network of small channels separated by small and often temporary islands called braid bars or, in British usage, aits or eyots. Braided streams occur in rivers with high slope and/or large sediment load. Braided channels are also typical of environments that dramatically decrease channel depth, and consequently channel velocity, such as river deltas, alluvial fans and peneplains.
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The ecosystem of a river is the river viewed as a system operating in its natural environment, and includes biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions.
River ecosystems are prime examples of lotic ecosystems. Lotic refers to flowing water, from the Latin lotus, washed. Lotic waters range from springs only a few centimeters wide to major rivers kilometers in width. Much of this article applies to lotic ecosystems in general, including related lotic systems such as streams and springs. Lotic ecosystems can be contrasted with lentic ecosystems, which involve relatively still terrestrial waters such as lakes and ponds. Together, these two fields form the more general study area of freshwater or aquatic ecology.
The following unifying characteristics make the ecology of running waters unique from that of other aquatic habitats.
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