A misfit stream is a river that is either too large or too small to have eroded the valley or cave passage in which it flows. This term is also used for a stream or river with meanders that obviously are not proportional in size to the meanders of the valley or meander scars cut into its valley walls. If the misfit stream is too large for either its valley or meanders, it is known as an overfit stream. If the misfit stream is too small for either its valley or meanders, it is known as an underfit stream.
[Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. ][Dury, G. H. (1964) ''Subsurface Exploration and Chronology of Underfit Streams.'' Professional Paper no. 452-A. U.S. Geological Survey, Reston, Virginia.]
The term ''misfit stream'' is often used as a synonym for an underfit stream.
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Origin
An underfit stream can result when glaciation
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate be ...
modifies the landscape by creating glacial troughs. The rivers that occupy such valleys after the ice has retreated are not in proportion with the size of the valley
A valley is an elongated low area often running between hills or mountains and typically containing a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over ...
. Given the scale of most glacial troughs almost all of them contain misfit streams. Misfit streams can also be caused by reductions in the discharge of the stream. Channel size responds rapidly to variations in discharge, but valley size responds over much longer timescales. Many causes of reduced discharges are possible. If misfit streams are widespread in an area, climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
, particularly a reduction in precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
, is likely to be the cause.[ If a single river appears to be a misfit stream, it may be as a result of human activity through ]groundwater
Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...
extraction or dam
A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...
construction upstream. Natural causes include stream capture
Stream capture, river capture, river piracy or stream piracy is a geomorphological phenomenon occurring when a stream or river drainage system or watershed is diverted from its own bed, and flows down to the bed of a neighbouring stream. This ...
or other changes in drainage patterns. For instance, New Zealand's largest river (the Waikato
The Waikato () is a region of the upper North Island of New Zealand. It covers the Waikato District, Waipā District, Matamata-Piako District, South Waikato District and Hamilton City, as well as Hauraki, Coromandel Peninsula, the nort ...
) used to flow through the Hauraki Plains to the North Island
The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...
's east coast, but changed its course to exit on the west coast due to a large volcanic eruption, leaving its former course through the 1-km wide Hinuera Gap occupied by only a small stream.
References
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External links
U.S. Geological Survey
further clarification of a misfit stream.
Water streams