A stream runs down a tundra valley floor between low, snow-capped mountains. Gravel chokes the stream bed, with water following many interweaving lines among large and small bars of the temporarily deposited sediment.
Dimensions The full stream bed is 30-40 feet (10-12 m) wide, with sloping banks 2-10 feet (0.6-3 m) high. Individual waterways are 1-10 feet (0.3-3 m) wide and very shallow.
Bars and stream-lines have no permanent positions within the stream bed. They gradually shift over days and weeks of normal water flow, and completely rearrange with the passage of floods.
In the shallow flowing water, grains of gravel tumble along, coming to rest only briefly before continuing their journey downstream. In mild weather the water is clear enough that an observer can follow a single pebble along many yards of its erratic path.
Flow will be very low to absent in colder parts of the year, when the surrounding tundra is entirely frozen and little melting is happening beneath mountain glaciers and snowfields upstream. The highest water levels occur in late summer, with most gravel bars submerged beneath turbulent water.
The surfaces of the largest bars are just at water level at their upstream ends, but stand a few inches above water level at their furthest downstream points, making it a significant step up from the water-covered stream bed to the dry gravel surface.
Where movement of the gravel grains is most active, the shifting nature of the streambed can be felt by a person treading it. Standing in one spot for a minute or so, the person will find small trenches being eroded in the gravel around the sides and upstream edge of each foot, and the gravel immediately underfoot starting to collapse.
When moving through the area, characters may want to follow the stream bed for ease of travel, but also will be exposed to observers.
As water cuts away at both bars of sediment and the river banks, hidden things might be revealed.
The shifting water courses prevent vegetation from developing in the stream bed. What other things might be similarly prevented or restrained by the flowing water?
Because the stream bed is loose gravel, someone’s sufficient strength, technology, magic, etc. could redirect the flow paths of the braided stream, locally changing aspects such as the number and position of the streamlets and depth and velocity of the stream.
Following a small, floating or submerged object of special interest downstream could be quite hectic, with a multitude of specific paths it might take through splits and re-joinings of the water flow. (This will be ripe with available metaphor for story line.)
An object buried along the stream bank could be quite effectively lost over time, if a temporary feature such as a large, distinctive bar is foolishly recorded as a location clue.
In the late summer and early fall, the tundra grassland surrounding the stream will be soft and mucky, with vegetation ‘sod’ mounds gradually sinking underfoot as they bear weight. The dry, relatively stable surface of a gravel bar in the river may afford a better spot for a siesta or overnight camp. This could work out just fine, or could lead to problems with an unexpected higher river flow, slow overnight erosion of an edge of the bar, or large creatures coming to the stream to drink.
A braided stream of this size, rarely having more than a few inches of water depth, can’t really be canoed. But a partly loaded canoe could be guided downstream on foot, or dragged upstream, so long as a careful eye is kept to follow the main channel-ways.
Hand-to-hand fights will have unexpected, splashing steps into water and stumbles onto dry gravel.
The step from water up onto a bar surface may be quite easy, or a difficult climb/jump up, depending on whether it’s the upstream or downstream end of the bar.
Because of the varying heights of the bars, characters may find themselves battling opponents higher or lower than themselves.
Headwaters of the Katinsha River, Denali National Park, south-central Alaska. (Braided streams, including much larger ones, are found in the mountains and grasslands of the western U.S. and similar climates/terrain around the world.)