An
entrenched river is a river that is confined to a
canyonA canyon, or gorge, is a deep valley between cliffs often carved from the landscape by a river. Most canyons were formed by a process of long-time erosion from a plateau level. The cliffs form because harder rock strata that are resistant to erosion and weathering remain exposed on the valley walls...
or gorge, usually with a relatively narrow width and little or no flood plain, and often with
meanderA meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a river erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternatively eroding sediments from the outside of a bend and depositing them on the...
s worn into the landscape. Such rivers form when the
base levelThe base level of a river or stream is the lowest point to which it can flow, often referred to as the 'mouth' of the river. For large rivers, sea level is usually the base level, but a large river or lake is likewise the base level for tributary streams...
of erosion is rapidly lowered, so that the river begins
downcuttingDowncutting, also called erosional downcutting or downward erosion or vertical erosion is a geological process that deepens the channel of a stream or valley by removing material from the stream's bed or the valley's floor. How fast downcutting occurs depends on the stream's base level, which is...
into its channel faster than it can change course (which rivers normally do on a constant basis). This may occur due to
tectonic upliftTectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...
of the region, a lowering of the oceans, the collapse of a moraine-dammed lake downstream, or by capture of the river by another.
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An
entrenched river is a river that is confined to a
canyonA canyon, or gorge, is a deep valley between cliffs often carved from the landscape by a river. Most canyons were formed by a process of long-time erosion from a plateau level. The cliffs form because harder rock strata that are resistant to erosion and weathering remain exposed on the valley walls...
or gorge, usually with a relatively narrow width and little or no flood plain, and often with
meanderA meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a river erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternatively eroding sediments from the outside of a bend and depositing them on the...
s worn into the landscape. Such rivers form when the
base levelThe base level of a river or stream is the lowest point to which it can flow, often referred to as the 'mouth' of the river. For large rivers, sea level is usually the base level, but a large river or lake is likewise the base level for tributary streams...
of erosion is rapidly lowered, so that the river begins
downcuttingDowncutting, also called erosional downcutting or downward erosion or vertical erosion is a geological process that deepens the channel of a stream or valley by removing material from the stream's bed or the valley's floor. How fast downcutting occurs depends on the stream's base level, which is...
into its channel faster than it can change course (which rivers normally do on a constant basis). This may occur due to
tectonic upliftTectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...
of the region, a lowering of the oceans, the collapse of a moraine-dammed lake downstream, or by capture of the river by another. Meanders established before the lowering of the base level of erosion may be preserved as the river channel deepens subsequently. Examples of entrenched meanders may be seen in the
Snake River CanyonSnake River Canyon is a large canyon formed by the Snake River in the Magic Valley region of southern Idaho. It is well known as the site of an unsuccessful 1974 attempt by Evel Knievel to jump it in the Skycycle X-2....
in southern
IdahoIdaho is a state in the Pacific Northwest region of the United States of America. The state's largest city and capital is Boise. Residents are called "Idahoans." Idaho was admitted to the Union on 3 July 1890 as the 43rd state....
, and in many canyons of the
Colorado PlateauThe Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km² within western Colorado, northwestern New Mexico,...
.