A hyperconcentrated flow is a two-phase flowing mixture of
water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
and
sediment
Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
in a channel which has properties intermediate between
fluvial
A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...
flow and
debris flow
Debris flows are geological phenomena in which water-laden masses of soil and fragmented Rock (geology), rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. ...
.
[Pierson, Thomas C. "Hyperconcentrated flow—transitional process between water flow and debris flow." Debris-flow hazards and related phenomena (2005): 159-202.] Large quantities of
sand
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...
may be transported throughout the flow column, but the transport of
suspended and
bedload
The term bed load or bedload describes particles in a flowing fluid (usually water) that are transported along the stream bed. Bed load is complementary to suspended load and wash load.
Bed load moves by rolling, sliding, and/or saltating (hop ...
sediment along the channel depends on flow
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between ...
and high flow velocities, and coarser sediment remains as
bedload
The term bed load or bedload describes particles in a flowing fluid (usually water) that are transported along the stream bed. Bed load is complementary to suspended load and wash load.
Bed load moves by rolling, sliding, and/or saltating (hop ...
. Hyperconcentrated flows do not show the characteristics of
non-Newtonian flow typical of debris flows, e.g.,
levee
A levee ( or ), dike (American English), dyke (British English; see American and British English spelling differences#Miscellaneous spelling differences, spelling differences), embankment, floodbank, or stop bank is an elevated ridge, natural ...
s,
coarsening up or
matrix supported deposits.
[Pierson, Thomas C. Distinguishing between debris flows and floods from field evidence in small watersheds. US Department of the Interior, US Geological Survey, 2005]
/ref>
Hyperconcentrated flows may contain anywhere from 5–60 % sediment by volume. Higher concentrations tend to be characteristic of debris flows, less of normal fluvial
A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...
flow.
References
Geological hazards
Fluvial geomorphology
{{geomorphology-stub