The following list defines some of the common terms associated with the principles of fluvial systems. Other helpful glossary resources include:

EPA Terms of the Environment:  Link

USGS Unofficial Glossary:  Link

The SUNY-ESF Fluvial Geomorphology Website:  Link

Water Quality Association of Terms:  Link

 

Active channel – The natural waterway that contains all streamflows at and below the bankfull discharge.

Aggradation – The process in which a steam’s gradient is increased as a result of an increase in sediment deposition. This may occur as a result of an increase in relative sediment load or a decrease in relative flow.

Bankfull stage – The elevation of the water surface when rising water completely fills the active channel and first begins to spill onto the local floodplain.

Cutbank – The outside edge of a stream meander where erosion is continually occurring and sediments contributed and transported within a fluvial system.

Degradation – The process in which a stream’s gradient is decreased as a result of an increase in flow and subsequent erosion/scouring and transportation of channel sediments from the stream bed. This may occur as a result of a decrease in relative sediment load or an increase in relative flow.

Deposition – The settling of material following a period of erosion and transportation.

Erosion – The loosening and subsequent transportation of material by means of water, air, and/or gravity.

Fluvial – A term that may describe any processes, deposits, or landforms that have been formed by, or relate to, rivers or streams.

Fluvial plain – The relatively flat area outside the active channel that makes up the valley floor (or valley flat). The fluvial plain represents the combination of depositional and erosional geomorphic features resulting from streamflow processes and most often includes the modern floodplain, local stream terraces, and abandoned meander scars.

Floodplain – The relatively flat valley-floor surface that has been constructed, during the present hydrologic regime, by the natural processes of point-bar deposition, lateral channel migration, and vertical accretion of sediments that have been transported beyond the active channel boundaries during periods of flooding.

Graded river – a fluvial system that, over a period of time, has developed a geometry, pattern, slope, and discharge that allows for the efficient transport of the debris and sediment loads within the channel, but retains no additional energy for erosion.

Meander – The naturally-occurring curves of a stream or river deviating from an otherwise linear course.

Point bar – The inner edge of a stream meander where deposition is continually occurring and sediments are deposited and stored within a fluvial system.

Riparian buffer – Any vegetated area located immediately adjacent to a stream that separates and protects the stream, and its associated habitat, from any alternative land uses.  Benefits may include the decreased surface runoff from urban or agricultural areas and reduction of fluvial erosion hazards as a result of increased bank stability.

Terrace – A generally flat valley-floor surface that represents an abandoned floodplain.  Terraces stand at elevations higher than the modern floodplain and can be formed through the processes of channel degradation or entrenchment.  Where there are multiple terraces in a cross-valley profile, they can be named according to their relative position above the active channel (for example, low, middle, high, etc…)

Watershed – The total land area that drains/contributes water to a particular stream, river, or lake.