Importance of channel erosion as a source of sediment

Abstract

A specific statement is not possible as to the percentage of total erosion caused by channel erosion. Watersheds containing tight soil may be almost entirely free of gullies, streams may have deep and narrow channels with stable banks, and slopes may be small, resulting in Little bed movement. On the other hand, watersheds draining upland sandy areas may have many gullies with rapid headward movement; channels may be shallow and wide, with such widening actively increasing at the present time; and steep slopes may cause a considerable amount of bed movement. Combinations of these factors may occur in a single watershed.Absence of sediment measuring stations on gullies makes volumetric estimates based on rate of change in depth, width, and headward movement necessary. Establishment of valley and channel range profiles is helpful in estimating bank erosion. It is being found that aerial photographs taken some years apart indicate that bank erosion may cause a greater part of the erosion in a watershed than was previously supposed. Confirmation of this is indicated by relatively permanent shifts in discharge rating curves. For bed movement reliance must be placed on current research and established formulas.