Meanders occur most commonly in channels that lie in fine-grained stream sediments and have gentle gradients.
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A river valley in a cross section is composed of edge, slope, base, bottom, channel and bed.
Streamline is a line of flow. It is an actual line connecting a series of fluid particles in a moving fluid so that, at a given instant, the velocity vector of every particle on that line is tangent to it.
When precipitation falls, water may not immediately soak in, run off, or evaporate.
The hydrologic cycle is off-balance because more liquid is brought in via comets and meteorites each year.