Bankfull stage

the point at which the flow just begins to enter the active floodplain. Accurate measurements have been conducted on gaged streams, however, in absence of historical hydrological records there are a number of field indicators that can be used to identify bankfull stages with a great deal of accuracy: • An abrupt change in the slope of the stream channel, usually from a vertical plane to a horizontal plane on top of the floodplain. • The bankfull stage is usually marked by a change in vegetation such as the change from gravel bars to forbs, herbs, or grasses. Persistent woody vegetation is usually indicative of upland terrain, but can be misleading. • Erosion or scour features. These features indicate areas just below the bankfull stage and are recognized as significant characteristics of stream dynamics. • Flat depositional benches, lateral bars, or point bars, usually created by lateral or downward movement of streams and can create active floodplain areas. • Change in the size distribution of sediment materials at the surface from fine gravel to cobbles, from sand to gravel or even fine gravel material. It can change from fine to coarse or coarse to fine. • Stain lines can indicate frequent inundation of water on rocks. Stain lines may be marked by sediment or lichens.

Glossary of Watershed Terms. (n.d.). Retrieved March 13, 2017, from http://www.coastalrcd.org/zone9/factsheets/glossary.html

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