Riffle

In these cases, scientists realized that the riverbed often tends to rise and fall with distance downstream relative to an average elevation of the river's slope.

That led scientists to map the bed elevation down the deepest path in a channel, called the thalweg, to obtain a longitudinal profile.

Then, the piecewise linear slope of the river is computed and removed to leave just the rise and fall of the elevation about the channel's trendline.

[6] For a long time, scientists have observed that, all other things being equal, riffles tend to be substantially wider than other in-channel landforms,[7] but only recently has there been high enough quality of river maps to confirm that this is true.

[13] Water with high and relatively stable levels of dissolved oxygen is typically considered to be a healthy ecosystem because it can generally support greater biodiversity and total biomass.

Litter patches are a collection of leaves, coarse particulate organic matter, and small woody stems that can be found throughout riffles.

[16] Also, food, shelter and low flow rates during the dry season make it a more habitable time for higher densities of macroinvertebrates.

[19] Specifically, weirs and other dams have reduced existing riffles by flattening the channel with smaller substrate, resulting in habitat fragmentation.

[18][21] The importance of riffles in supporting diverse assemblages of aquatic biota within streams and rivers may contribute to the increasing trend of dam removal.