You do not have permission to edit this page, for the following reasons:

This IP address has been blocked from editing Wikipedia.
This does not affect your ability to read Wikipedia pages.
Most people who see this message have done nothing wrong. Some kinds of blocks restrict editing from specific service providers or telecom companies in response to recent abuse or vandalism, and can sometimes affect other users who are unrelated to that abuse. Review the information below for assistance if you do not believe that you have done anything wrong.

The IP address or range 35.172.0.0/16 has been blocked (disabled) by ‪JJMC89‬ for the following reason(s):

The IP address that you are currently using has been blocked because it is believed to be a web host provider or colocation provider. To prevent abuse, web hosts and colocation providers may be blocked from editing Wikipedia.
You will not be able to edit Wikipedia using a web host or colocation provider because it hides your IP address, much like a proxy or VPN.
We recommend that you attempt to use another connection to edit. For example, if you use a proxy or VPN to connect to the internet, turn it off when editing Wikipedia. If you edit using a mobile connection, try using a Wi-Fi connection, and vice versa. If you are using a corporate internet connection, switch to a different Wi-Fi network. If you have a Wikipedia account, please log in.
If you do not have any other way to edit Wikipedia, you will need to request an IP block exemption.

How to appeal if you are confident that your connection does not use a colocation provider's IP address:
If you are confident that you are not using a web host, you may appeal this block by adding the following text on your talk page: ((unblock|reason=Caught by a colocation web host block but this host or IP is not a web host. My IP address is _______. Place any further information here. ~~~~)). You must fill in the blank with your IP address for this block to be investigated. Your IP address can be determined here. Alternatively, if you wish to keep your IP address private you can use the unblock ticket request system. There are several reasons you might be editing using the IP address of a web host or colocation provider (such as if you are using VPN software or a business network); please use this method of appeal only if you think your IP address is in fact not a web host or colocation provider.

Administrators: The IP block exemption user right should only be applied to allow users to edit using web host in exceptional circumstances, and requests should usually be directed to the functionaries team via email. If you intend to give the IPBE user right, a CheckUser needs to take a look at the account. This can be requested most easily at SPI Quick Checkuser Requests. Unblocking an IP or IP range with this template is highly discouraged without at least contacting the blocking administrator.

This block will expire on 05:20, 2 July 2025.

Even when blocked, you will usually still be able to edit your user talk page, as well as email administrators and other editors.

For information on how to proceed, please read the FAQ for blocked users and the guideline on block appeals. The guide to appealing blocks may also be helpful.

Other useful links: Blocking policy · Help:I have been blocked
Your IP address is in a range that has been blocked on all Wikimedia Foundation wikis. The block was made by ‪Tks4Fish‬. The reason given is Open Proxy/Webhost: Contact stewards if you are affected. .
- Start of block: 04:10, 17 February 2021
- Expiry of block: 04:10, 17 February 2024
Your current IP address is 35.172.110.109. The blocked range is 35.172.0.0/16. Please include all above details in any queries you make. If you believe you were blocked by mistake, you can find additional information and instructions in the No open proxies global policy. Otherwise, to discuss the block please post a request for review on Meta-Wiki. You could also send an email to the stewards VRT queue at stewards@wikimedia.org including all above details.

You can view and copy the source of this page:

((Short description|Point on a stream's profile where a sudden change in stream gradient occurs))
((refimprove|date=December 2015))
[[Image:Niagara watervallen canada.jpg|250px|right|thumb|The [[Horseshoe Falls, Canada|Horseshoe Falls]], one of the three Niagara Falls. The falls are a knickpoint, formed by slower erosion above the falls than below.]]

In [[geomorphology]], a '''knickpoint''' or '''nickpoint''' is part of a [[river]] or [[Channel (geography)|channel]] where there is a sharp change in [[channel bed]] [[Grade (slope)|slope]], such as a [[waterfall]] or [[lake]]. Knickpoints reflect different conditions and processes on the river, often caused by previous [[erosion]] due to [[glaciation]] or variance in [[lithology]]. In the [[cycle of erosion]] model, knickpoints advance one cycle upstream, or inland, replacing an older cycle.<ref name=Migon>((cite encyclopedia|last=Tinkler|first=Keith J.|editor-last=Goudie|editor-first=A.S.|editor-link=Andrew Goudie (geographer)|encyclopedia=Encyclopedia of Geomorphology|title=Knickpoint|year=2004|pages=595–596))</ref> A knickpoint that occurs at the head (furthest upstream extent) of a channel is called a [[head cut (stream geomorphology)|headcut]].<ref name = 'Bierman'> ((cite book |first1=Paul |last1=Bierman |first2 = David |last2= Montgomery |title =Key Concepts in Geomorphology |year= 2013 |url=https://b-ok.org/book/3490407/245682)) </ref> [[head cut (stream geomorphology)|Headcuts]] resulting in [[headward erosion]] are hallmarks of unstable expanding drainage features such as actively eroding gullies.<ref name= 'Knighton'>((cite book |first = David |last = Knighton |year = 1998 |title = Fluvial Forms and Processes, A New Perspective |url=https://scholar.google.com/scholar?q=knighton%20fluvial%20forms%20and%20processes)) </ref>

Knickpoints also occur on other planetary bodies that previously had or currently have surface liquids, namely [[Mars]]<ref name=":1">((Cite journal|last1=Duran|first1=Sergio|last2=Coulthard|first2=Tom J.|last3=Baynes|first3=Edwin R. C.|date=2019-10-22|title=Knickpoints in Martian channels indicate past ocean levels|journal=Scientific Reports|language=en|volume=9|issue=1|pages=15153|doi=10.1038/s41598-019-51574-2|pmid=31641171|pmc=6805925|bibcode=2019NatSR...915153D|issn=2045-2322|doi-access=free))</ref> and [[Titan (moon)|Titan]].<ref name=":2">((Cite journal|last1=Lucas|first1=Antoine|last2=Aharonson|first2=Oded|last3=Deledalle|first3=Charles|last4=Hayes|first4=Alexander G.|last5=Kirk|first5=Randolph|last6=Howington‐Kraus|first6=Elpitha|date=2014|title=Insights into Titan's geology and hydrology based on enhanced image processing of Cassini RADAR data|journal=Journal of Geophysical Research: Planets|language=en|volume=119|issue=10|pages=2149–2166|doi=10.1002/2013JE004584|bibcode=2014JGRE..119.2149L|issn=2169-9100|doi-access=free))</ref> On Mars, the knickpoints have a common elevation that suggest a common sea level for a [[Martian ocean|former Martian ocean]].<ref name=":1" /> On Titan, mountain valleys adjacent to the present-day [[Lakes of Titan|hydrocarbon seas]] show evidence of knickpoints and recent [[Sea level change|sea-level change]].<ref name=":2" />

== Formation ==

Knickpoints are formed by the influence of tectonics, climate history, and/or lithology.<ref>Paul R. Bierman, David R. Montgomery. ''Key Concepts in Geomorphology'', Freeman, 2013 ((ISBN|978-1429238601))</ref> For example, uplift along a fault over which a river is flowing will often result in an unusually steep reach along a channel, known as a ''knickzone''. Glaciation resulting in a  [[hanging valley]] are often prime spots for knickpoints. If lithology of the rock varies, such as shale amongst igneous rock, erosion will occur more steadily in the softer rock than the surrounding, tougher rock.

Base level is the elevation of the surface of the water body into which a river ultimately drains, usually the ocean. A drop in base level causes a response by the river system to carve into the landscape. This incision begins at the formation of a knickpoint, and its upstream migration depends heavily upon the drainage area (and so the discharge of the river), material through which it cuts, and how large the drop in base level was.<ref name=":0">((Cite journal|title = Wave train model for knickpoint migration|journal = Geomorphology|date = 2009-05-15|pages = 376–382|volume = 106|issue = 3–4|doi = 10.1016/j.geomorph.2008.10.017|first1 = Nicolas|last1 = Loget|first2 = Jean|last2 = Van Den Driessche|bibcode = 2009Geomo.106..376L|url = https://archimer.ifremer.fr/doc/00000/11075/))</ref>

== Modern examples ==
[[File:Satellite view of Victoria Falls.jpg|thumb|In this satellite image of Victoria Falls, the gorges below the falls as well as developing crevasses below the surface of the river are visible. As the knickpoint recedes upstream, these crevasses will become, in turn, the location of the Falls.]]
Knickpoints include both waterfalls and some lakes. These features are common in rivers with a sufficient [[slope]], i.e. enough change in [[Elevation|elevation above sea level]] over their length to encourage [[Degradation (geology)|degradation]].

=== Influenced by lithology ===
Variations in stability of the underlying rock influence development of a bedrock-channeled river, as the waters erode different rock types at different rates. [[Victoria Falls, Zambia|Victoria Falls]], on the [[Zambezi|Zambezi River]], is a spectacular example of this. The gorges visible by satellite imagery illustrate the [[erosion]]al processes behind the formation of the falls. Here, much of the surface rock is a massive [[basalt]] [[Sill (geology)|sill]], with large cracks filled with easily weathered [[sandstone]] made visible by the Zambezi's course across the land. The [[Canyon|gorges]] downstream of the falls through which it flows were eroded over time by the action of the water.

=== Influenced by tectonic activity ===
Throughout [[New Zealand]], tectonic uplift and faulting are actively contributing to knickpoint initiation and recession. The [[Waipoua River (Northland)|Waipoua River system]], on the North island, has been studied and used to create mathematical models to predict the behavior of knickpoints.<ref>((Cite journal|title = Knickpoint initiation and distribution within fluvial networks: 236 waterfalls in the Waipaoa River, North Island, New Zealand|journal = Geomorphology|date = 2006-12-06|pages = 16–38|volume = 82|series = The Hydrology and Geomorphology of Bedrock Rivers|issue = 1–2|doi = 10.1016/j.geomorph.2005.08.023|first1 = Benjamin T.|last1 = Crosby|first2 = Kelin X.|last2 = Whipple|bibcode = 2006Geomo..82...16C))</ref> The study showed a direct correlation between upstream [[Drainage basin|drainage area]] and rate of migration, producing modeled data closely approximating the collected data. The Waipoua River system incises through [[sediment]]s, for the most part, as opposed to [[bedrock]].

=== Influenced by glacial activity ===
[[File:Yosemite Bridalveil falls.JPG|thumb|upright|Bridalveil Fall, in Yosemite, flows over the edge of a glacially-carved hanging valley.]]
Sharp changes in slope are common in rivers flowing through the heavily carved landscape left behind when [[glacier]]s retreat. [[Glacial valley]]s, as well as [[isostatic rebound]] resulting from the removal of the mass of glacial ice contribute to this.

[[Niagara Falls]], on the border of the United States and Canada, is a characteristic example of knickpoint.  The falls have slowed in migration from approximately 1m per year as of 1900 to their modern 10&nbsp;cm per year.<ref>((Cite journal|title = Factors influencing the recession rate of Niagara Falls since the 19th century|journal = Geomorphology|date = 2009-09-15|pages = 212–216|volume = 110|issue = 3–4|doi = 10.1016/j.geomorph.2009.04.011|first1 = Yuichi S.|last1 = Hayakawa|first2 = Yukinori|last2 = Matsukura|bibcode = 2009Geomo.110..212H|hdl = 2241/103715|url = https://tsukuba.repo.nii.ac.jp/?action=repository_action_common_download&item_id=18232&item_no=1&attribute_id=17&file_no=1|hdl-access = free))</ref> The falls, particularly [[Horseshoe Falls]], are dramatically steep and caused by [[Wisconsin glaciation|glaciation]]. The [[Great Lakes]] themselves lie in the depressions left behind by glaciers, as the crust is still [[Post-glacial rebound|rebounding]].

[[Bridalveil Fall]], in [[Yosemite Valley]], California, pours over the lip of a [[hanging valley]].

== Paleomorphology ==
[[File:Dry Falls (Washington).jpg|thumb|Dry Falls, Washington: a prehistoric knickpoint]]
Evidence of a knickpoint in the geologic past can be preserved in the shape of the bedrock below any subsequent depositions, as well as within sedimentary depositions left unchanged by human or other activity. Lakes characteristically fill in with sediment over time, but waterfalls often erode away. There are few obvious, dry examples still visible today of prehistoric knickpoints.

=== Evidence of massive prehistoric flooding ===
[[Dry Falls]], a 3.5&nbsp;mi long precipice in central [[Washington (state)|Washington]], is an example of an ancient knickpoint. Geologic evidence strongly suggests that the water which formed this feature flowed over the [[Channeled Scablands]], [[Glacial lake outburst flood|bursting]] from the [[glacial lake]] [[Lake Missoula|Missoula]] during an event known as the [[Missoula Floods]] and into the [[Columbia River Gorge]].

=== Evidence within karst topography ===
On the [[Cumberland River|Upper Cumberland River]], [[Tennessee]], there exist a series of hydrologically abandoned [[cave]]s which still hold river-deposited sediments. These caves were the subject of an effort to measure the rate of knickpoint migration along the river, as well as to approximate the [[Discharge (hydrology)|discharge]] of the river over time.<ref>((Cite journal|title = An empirical stream power formulation for knickpoint retreat in Appalachian Plateau fluviokarst|journal = Journal of Hydrology|date = 2007-09-20|pages = 117–126|volume = 343|issue = 3–4|doi = 10.1016/j.jhydrol.2007.06.013|first1 = Darlene M.|last1 = Anthony|first2 = Darryl E.|last2 = Granger|bibcode = 2007JHyd..343..117A))</ref> In [[karst topography]], a river dropping in level influences more than just its [[River channel|channel]]; as there is no longer water flowing at a certain level, caves and [[water table]]s will drop locally to the new level.

=== Evidence of large-scale base level drop ===
Large drainages into the oceans the world over can be seen to have continued over land which was once exposed, whether due to tectonic subsidence, [[sea level rise]], or other factors. [[Bathymetry|Bathymetric]] imagery is available for much of the United States' western coast, and in particular the [[Continental margin|ocean floor just offshore]] of rivers in the Pacific Northwest exhibit such underwater features.

In certain locations there are still knickpoints preserved in these drowned river channels and valleys. A study conducted within the [[Mediterranean Sea|Mediterranean basin]]<ref name=":0" /> focused on such features. Here, incision was caused by the [[Geology and paleoclimatology of the Mediterranean Basin|closing of the Mediterranean]] at the end of the [[Miocene]]. This sudden lack of ocean water influx allowed the basin to decrease in volume and increase in [[Messinian salinity crisis|salinity]], and as a result of the drop in surface level many of the rivers which flow still today into the Mediterranean began to incise.<ref name=":0" />

== Movement ==
As is observed for many major waterfalls, knickpoints migrate upstream due to bedrock erosion<ref>[http://www.uvm.edu/cosmolab/projects/potomac/potomac.html Paul Bierman, Milan Pavich, E-an Zen, and Marc Caffee, ''Determining Rates and Patterns of Bedrock Incision by Large Rivers''] ((webarchive|url=https://web.archive.org/web/20070913075400/http://www.uvm.edu/cosmolab/projects/potomac/potomac.html |date=2007-09-13 ))</ref> leaving in their wake deep channels and abandoned [[floodplain]]s, which then become [[River terraces (tectonic–climatic interaction)|terraces]]. Knickpoint retreat is easily demonstrated in some locations affected by [[Post-glacial rebound|postglacial isostatic]] response and relative sea-level drop such as in [[Scotland]]. In other areas, dating of exposed bedrock terraces is more consistent with spatially uniform incision and persistence of the knickzone at about the same location.

A river, having gained or lost [[potential energy]] with its changed [[slope]], will then proceed to work the knickpoints out of its system by either erosion (in the case of waterfalls; gained potential energy) or deposition (in the case of lakes; lost potential energy) in order for the river to reattain its smooth concave graded profile.

The rates of knickpoint migration, in the case of waterfalls, generally range between 1mm and 10&nbsp;cm per year, with some exceptional values.<ref name=":0" />

=== Mathematical modeling ===
Knickpoint propagation is typically modelled with the semi empirical [[stream power law]] where the [[drainage basin]] size is used as a proxy for [[Discharge (hydrology)|discharge]], which in turn has a [[Positive correlation|positive nonlinear correlation]] to the rate of knickpoint migration.
Both analytical
<ref>((Cite journal|title = Solutions of the stream power equation and application to the evolution of river longitudinal profiles|journal = J. Geophys. Res. Earth Surf.|date = 2013-05-02|pages = 497–518|volume = 118|issue = 2|doi=10.1002/jgrf.20031|first1 = Leigh|last1 = Royden |authorlink=Leigh Royden |first2 = Taylor|last2 = Perron|bibcode = 2013JGRF..118..497R|hdl = 1721.1/85608| s2cid=15647009 |hdl-access = free))</ref>
and numerical solutions
<ref>((Cite journal|title = Keeping the edge: A numerical method that avoids knickpoint smearing when solving the stream power law|journal = J. Geophys. Res. Earth Surf.|date = 2015-07-08|pages = 1189–1205|volume = 120|issue = 7|doi=10.1002/2014JF003376|first1 = Benjamin|last1 = Campforts|first2 = Gerard|last2 = Govers|bibcode = 2015JGRF..120.1189C|doi-access = free))</ref> have been proposed to solve the [[stream power law]].

== Automated extraction in GIS ==
Knickpoints and knickzones can be semiautomatically extracted from [[Digital elevation model|Digital Elevation Models]] in [[Geographic information system|Geographic Information System]] software (i.e. [[ArcGIS]]). The problem with most of existing methods is that they are frequently subjective and require time-consuming data processing. A solution for these problems is a tool designed for ArcGIS, called Knickzone Extraction Tool (KET) which vastly automates the extraction process.<ref>((Cite journal|last1=Zahra|first1=Tuba|last2=Paudel|first2=Uttam|last3=Hayakawa|first3=Yuichi|last4=Oguchi|first4=Takashi|date=2017-04-24|title=Knickzone Extraction Tool (KET) – A new ArcGIS toolset for automatic extraction of knickzones from a DEM based on multi-scale stream gradients|journal=Open Geosciences|volume=9|issue=1|pages=73–88|doi=10.1515/geo-2017-0006|bibcode=2017OGeo....9....6Z|issn=2391-5447|doi-access=free))</ref>

== See also ==
((portal|Environment))
* [[Hydrology]]
* [[Stream gradient]]

== References ==
((reflist))

((river morphology))

[[Category:Geomorphology]]
[[Category:Fluvial landforms]]
[[Category:Erosion landforms]]

Pages transcluded onto the current version of this page (help):

Knickpoint (edit)
Template:Ambox (view source) (template editor protected)
Template:Catalog lookup link (view source) (template editor protected)
Template:Cite book (view source) (protected)
Template:Cite encyclopedia (view source) (protected)
Template:Cite journal (view source) (protected)
Template:Find sources mainspace (view source) (template editor protected)
Template:Hlist/styles.css (view source) (protected)
Template:ISBN (view source) (template editor protected)
Template:Icon (view source) (template editor protected)
Template:Main other (view source) (protected)
Template:More citations needed (view source) (template editor protected)
Template:Navbox (view source) (template editor protected)
Template:Pagetype (view source) (protected)
Template:Portal (view source) (template editor protected)
Template:Refimprove (view source) (template editor protected)
Template:Reflist (view source) (protected)
Template:Reflist/styles.css (view source) (protected)
Template:River morphology (edit)
Template:SDcat (view source) (template editor protected)
Template:Short description (view source) (protected)
Template:Short description/lowercasecheck (view source) (protected)
Template:Webarchive (view source) (template editor protected)
Template:Yesno (view source) (protected)
Template:Yesno-no (view source) (template editor protected)
Template:Yesno-yes (view source) (template editor protected)
Module:Arguments (view source) (protected)
Module:Catalog lookup link (view source) (template editor protected)
Module:Category handler (view source) (protected)
Module:Category handler/blacklist (view source) (protected)
Module:Category handler/config (view source) (protected)
Module:Category handler/data (view source) (protected)
Module:Category handler/shared (view source) (protected)
Module:Check for unknown parameters (view source) (protected)
Module:Check isxn (view source) (template editor protected)
Module:Citation/CS1 (view source) (protected)
Module:Citation/CS1/COinS (view source) (protected)
Module:Citation/CS1/Configuration (view source) (protected)
Module:Citation/CS1/Date validation (view source) (protected)
Module:Citation/CS1/Identifiers (view source) (protected)
Module:Citation/CS1/Utilities (view source) (protected)
Module:Citation/CS1/Whitelist (view source) (protected)
Module:Citation/CS1/styles.css (view source) (protected)
Module:Disambiguation (view source) (protected)
Module:Disambiguation/templates (view source) (protected)
Module:Find sources (view source) (template editor protected)
Module:Find sources/config (view source) (template editor protected)
Module:Find sources/links (view source) (template editor protected)
Module:Find sources/templates/Find sources mainspace (view source) (template editor protected)
Module:Icon (view source) (template editor protected)
Module:Icon/data (view source) (template editor protected)
Module:Message box (view source) (protected)
Module:Message box/ambox.css (view source) (protected)
Module:Message box/configuration (view source) (protected)
Module:Namespace detect/config (view source) (protected)
Module:Namespace detect/data (view source) (protected)
Module:Navbar (view source) (protected)
Module:Navbar/configuration (view source) (protected)
Module:Navbar/styles.css (view source) (protected)
Module:Navbox (view source) (template editor protected)
Module:Navbox/configuration (view source) (template editor protected)
Module:Navbox/styles.css (view source) (template editor protected)
Module:Pagetype (view source) (protected)
Module:Pagetype/config (view source) (protected)
Module:Portal (view source) (template editor protected)
Module:Portal/images/e (view source) (template editor protected)
Module:Portal/styles.css (view source) (template editor protected)
Module:Redirect (view source) (protected)
Module:SDcat (view source) (template editor protected)
Module:String (view source) (protected)
Module:Unsubst (view source) (protected)
Module:Webarchive (view source) (template editor protected)
Module:Webarchive/data (view source) (template editor protected)
Module:Yesno (view source) (protected)

Return to Knickpoint.

Retrieved from "https://en.wikipedia.org/wiki/Knickpoint"