Water gap

Geological feature formed through a mountain

For other uses, see Water gap (disambiguation).

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The Columbia River cut the Wallula Gap, seen from Main Street in Wallula, Washington

A water gap is a gap that flowing water has carved through a mountain range or mountain ridge and that still carries water today.[1] Such gaps that no longer carry water currents are called wind gaps. Water gaps and wind gaps often offer a practical route for road and rail transport to cross the mountain barrier.

## Geology

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View of water gaps cut by the Raystown Branch of the Juniata River through Evitts Mountain and Tussey Mountain, facing west from the summit of Kinton Knob, Wills Mountain, in Bedford County, Pennsylvania, with the town of Bedford in the foreground

A water gap is usually an indication of a river that is older than the current topography. The likely occurrence is that a river established its course when the landform was at a low elevation, or by a rift in a portion of the crust of the earth having a very low stream gradient and a thick layer of unconsolidated sediment.

In a hypothetical example, a river would have established its channel without regard for the deeper layers of rock. A later period of uplift would cause increased erosion along the riverbed, exposing the underlying rock layers. As the uplift continued, the river, being large enough, would continue to erode the rising land, cutting through ridges as they formed.

Water gaps are common in the Ridge-and-Valley Appalachians of eastern North America.

Alternatively, a water gap may be formed through headward erosion of two streams on opposite sides of a ridge, ultimately resulting in the capture of one stream by the other.

## Notable examples

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Two water gaps opened by the same river in central Pennsylvania, foreground and background, separated by settlements in flat lands

* Chicago Portage, Illinois \- Saddle Point runs through the city itself.
* Columbia River Gorge, Oregon and Washington, and Wallula Gap, Washington, United States
* Cumberland Narrows, Maryland, United States
* Delaware Water Gap, New Jersey and Pennsylvania, United States[2]
* Digby Gut, Nova Scotia, through which the Annapolis River flows into the Bay of Fundy
* Heavitree Gap, Alice Springs, Australia
* Iron Gates on the Danube River, forming the border between Serbia and Romania
* Kali Gandaki Gorge \- cuts through the world's tallest mountain range, the Himalayas in Nepal
* Manawatū Gorge, New Zealand
* Middle Rhine in Germany
* Pongo de Mainique, Peru - on the Urubamba River
* Pongo de Manseriche, Peru - on the Marañón River
* Potomac Water Gap, United States
* Weltenburg Narrows on the Danube River in Bavaria
* Wawa Gorge, Rodriguez, Rizal, Philippines

## References

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1. ^ Creation Research Society (2010). Creation Research Society Quarterly Vol. 47 No. 1 Summer 2010.
2. ^ "Delaware Water Gap". National Park Service. Retrieved 23 December 2023.

## See also

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* Antecedent drainage stream
* Defile (geography)
* Narrows
* Peneplain

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Rivers, streams and springs

Rivers
(lists)|

* Alluvial river
* Braided river
* Blackwater river
* Channel
* Channel pattern
* Channel types
* Confluence
* Distributary
* Drainage basin
* Subterranean river
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* River ecosystem
* River source
* Tributary

Streams|

* Arroyo
* Beck
* Bourne
* Burn
* Chalk stream
* Coulee
* Current
* Stream bed
* Stream channel
* Streamflow
* Stream gradient
* Stream pool
* Perennial stream
* Winterbourne

Springs
(list)|

* Estavelle/Inversac
* Geyser
* Holy well
* Hot spring
* list
* list in the US
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* list
* Mineral spring
* Ponor
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* Spring horizon

Sedimentary processes
and erosion|

* Abrasion
* Anabranch
* Aggradation
* Armor
* Bed load
* Bed material load
* Granular flow
* Debris flow
* Deposition
* Dissolved load
* Downcutting
* Erosion
* Headward erosion
* Knickpoint
* Palaeochannel
* Progradation
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* Saltation
* Secondary flow
* Sediment transport
* Suspended load
* Wash load
* Water gap

Fluvial landforms|

* Ait
* Alluvial fan
* Antecedent drainage stream
* Avulsion
* Bank
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* Canyon
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* Glen
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* Mouth bar
* Oxbow lake
* Riffle-pool sequence
* Point bar
* Ravine
* Rill
* River island
* Rock-cut basin
* Sedimentary basin
* Sedimentary structures
* Strath
* Thalweg
* River valley
* Wadi

Fluvial flow|

* Helicoidal flow
* International scale of river difficulty
* Log jam
* Meander
* Plunge pool
* Rapids
* Riffle
* Shoal
* Stream capture
* Waterfall
* list of waterfalls
* Whitewater

Surface runoff|

* Agricultural wastewater
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Floods and stormwater|

* 100-year flood
* Crevasse splay
* Flash flood
* Flood
* Urban flooding
* Non-water flood
* Flood barrier
* Flood control
* Flood forecasting
* Flood-meadow
* Floodplain
* Flood pulse concept
* Flooded grasslands and savannas
* Inundation
* Storm Water Management Model
* Return period

Point source pollution|

* Effluent
* Industrial wastewater
* Sewage

River measurement
and modelling|

* Baer's law
* Baseflow
* Bradshaw model
* Discharge (hydrology)
* Drainage density
* Exner equation
* Groundwater model
* Hack's law
* Hjulström curve
* Hydrograph
* Hydrological model
* Hydrological transport model
* Infiltration (hydrology)
* Main stem
* Playfair's law
* Relief ratio
* River Continuum Concept
* Rouse number
* Runoff curve number
* Runoff model (reservoir)
* Stream gauge
* Universal Soil Loss Equation
* WAFLEX
* Wetted perimeter
* Volumetric flow rate

River engineering|

* Aqueduct
* Balancing lake
* Canal
* Check dam
* Dam
* Drop structure
* Daylighting
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* Erosion control
* Fish ladder
* Floodplain restoration
* Flume
* Infiltration basin
* Leat
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* River morphology
* Retention basin
* Revetment
* Riparian-zone restoration
* Stream restoration
* Weir

River sports|

* Canyoning
* Fly fishing
* Rafting
* River surfing
* Riverboarding
* Stone skipping
* Triathlon
* Whitewater canoeing
* Whitewater kayaking
* Whitewater slalom

Related|

* Aquifer
* Aquatic toxicology
* Body of water
* Hydraulic civilization
* Limnology
* Riparian zone
* River valley civilization
* River cruise
* Sacred waters
* Surface water
* Wild river

* Rivers by length
* Rivers by discharge rate
* Drainage basins
* Whitewater rivers
* Flash floods
* River name etymologies
* Countries without rivers

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