Rivers in Action Many rivers begin as melting snow high in scenic mountains, often leaping to life as rocky rapids or cascading waterfalls. As they enter lowlands, rivers begin to run more slowly, growing in size as they re fed by other rivers and streams. They generally become a little less clear as their load of silt grows. Rivers never flow in a perfectly straight line. Rather, they follow the path of least resistance, funneling down a tiny valley or flowing around a giant boulder.
Some rivers meander like drunken snakes.
Meandering loops may eventually be cut off, forming isolated lakes called oxbows . Rivers may split into several separate channels , forming a braided river . Eventually, a river or stream reaches its mouth , the location where it enters the sea. As the river spreads out and is slowed by the sea, sediments carried by the river settle to the bottom. As these sediments accumulate, they form a delta , typically triangular in shape.