River erosion is a powerful shaper of topography, cutting through bedrock and over time converting smooth terrain to rolling hills or jagged cliffs. The rate of bedrock incision is influenced by the stream's slope and width, the water's flow rate, and the presence of sediment, among other factors. Researchers know sediment can play two conflicting roles: If the river's sediment load is low, it acts like sandpaper, increasing the rate of riverbed erosion. If there is plentiful sediment in the river, it forms a protective barrier along the riverbed, limiting erosion. What remains uncertain, however, is the influence of large, periodic inputs of sediment that enter rivers because of landslides or other extreme events.

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