38:
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159:, which can create greater variety in local geomorphology and thus create provision and variety of habitat for instream living organisms. The formation of a log jam against one bank typically concentrates flow in the wood-free portion of the channel, increasing velocity through this section and promoting
210:
of the United States, it has been shown there is a lifecycle of tree growth and river migration, with large trees falling into the channel as banks erode, then staying in place and acting as focal points for log jam formation. These log jams act as hard points, resisting further erosion and channel
166:
The hydraulic and geomorphological effects of log jams are highly dependent on the slope of the river (and thus the potential power of the stream); in steep channels, log jams tend to form channel-spanning steplike structures with an associated downstream scour pool, whereas in large lowland rivers
219:"Logjam" or "log jam" can be used metaphorically to mean "deadlock" or "impasse." It can be used either more literally, to mean a physical impasse, or more metaphorically, to mean an impasse in a process due to differing opinions, legal or technical issues, etc. Here are two example sentences:
100:, which prior to its removal in the 1830s affected between 390 and 480 km (240–300 mi) of the main channel. It has been suggested that such extensive log rafts may have been common in Europe in prehistory. Currently, the largest known log jam is over 3 million tonnes in the
154:
hydraulics by diverting flow towards the bed or banks, increasing flow resistance and creating upstream pools, diverting flow onto the floodplain and damming the channel, causing water to spill over the structure. These altered channel hydraulics change local patterns of erosion and
202:
and promote the formation of stable islands in the river. These stable islands are then prime areas for establishment of seedlings and further vegetation growth, which in turn can eventually provide more fallen trees to the river and thus form more log jams.
85:. Unless they are dismantled by natural causes or humans, log jams can grow quickly, as more wood arriving from upstream becomes entangled in the mass. Log jams can persist for many decades, as is the case with the log jam in Spirit Lake.
61:" is commonly defined to be pieces of wood more than 10 cm (4 in) in diameter and more than 1 m (3 ft 3 in) long.) Log jams in rivers and streams often span the entirety of the water's surface from
37:
183:. These pools also provide refuge for fish during low water levels when other parts of a stream may be nearly dry. Log jams can provide refuge, as velocity shelters, during high-flow periods.
163:
of the riverbed. The formation of channel-spanning log jams can lead to the formation of an upstream pool, water spilling over the structure generating a "plunge pool" immediately downstream.
211:
migration. The areas of floodplain behind these log jams then become stable enough for more large trees to grow, which can in turn become potential log jam anchor points in the future.
69:, or other objects anchored underwater. They can build up slowly over months or years, or they can happen instantaneously when large numbers of trees are swept into the water after
842:"The floodplain large-wood cycle hypothesis: A mechanism for the physical and biotic structuring of temperate forested alluvial valleys in the North Pacific coastal ecoregion"
57:
is a naturally occurring phenomenon characterized by a dense accumulation of tree trunks and pieces of large wood across a vast section of a river, stream, or lake. ("Large
88:
Historically in North
America, large natural "log rafts" were common across the continent prior to European settlement. The most famous natural wood raft is the
198:, fallen trees form log jams when they are deposited on bars; fine sediment is deposited around these log jams, and sprouting seedlings are able to stabilise
186:
It has been suggested that log jams are an aspect of trees acting as ecosystem engineers to alter river habitats to promote tree growth. In dynamic
111:. It contains more than 400,000 caches of wood and stores 3.4 million tons of carbon, equivalent to a year's emissions from 2.5 million cars.
603:
Gurnell, A.M.; Gregory, K.J.; Petts, G.E. (1995). "The role of coarse woody debris in forest aquatic habitats: Implications for management".
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65:
to bank. Log jams form when trees floating in the water become entangled with other trees floating in the water or become snagged on rocks,
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223:"The presence of an ambulance on the side of the highway created a logjam of rubberneckers who just had to have a look." (more literal).
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82:
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with low slopes, log jams tend to be partial structures primarily acting to deflect flow with minimal geomorphological change.
410:
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habitat. The pools created and sediment deposited by formation of log jams create prime spawning grounds for many species of
688:
Curran, J.C.; Wohl, E.E. (2003). "Large woody debris and flow resistance in step-pool channels, Cascade Range, Washington".
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Abbe, T.B.; Montgomery, D.R. (1996). "Large woody debris jams, channel hydraulics and habitat formation in large rivers".
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Montgomery, D.R.; Collins, B.D.; Buffington, J.M.; Abbe, T.B. (2003). "Geomorphic effects of wood in rivers".
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448:"Wood-Based Carbon Storage in the Mackenzie River Delta: The World's Largest Mapped Riverine Wood Deposit"
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Shields, F.D.; Gippel, C.J. (1995). "Prediction of effects of woody debris removal on flow resistance".
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Sendrowski, Alicia; Wohl, Ellen; Hilton, Robert; Kramer, Natalie; Ascough, Philippa (16 April 2023).
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Gurnell, A.M.; Petts, G.E. (2006). "Trees as riparian engineers: The
Tagliamento River, Italy".
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497:"World's biggest cumulative logjam mapped in the N.W.T. — and it stores tons of carbon"
226:"He was called in to try to break the logjam in the negotiations." (more metaphorical).
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73:. A notable example caused by a natural disaster is the log jam that occurred in
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Accumulation of large wood in a stream or river, preventing movement downstream
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10.1002/(sici)1099-1646(199603)12:2/3<201::aid-rrr390>3.3.co;2-1
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or the intentional release of large masses of trees into the water during a
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This article is about river debris. For the cryptographic exploit, see
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Collins, B.D.; Montgomery, D.R; Fetherston, K.L.; Abbe, T.B. (2012).
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640:"A dimensionless statistical analysis of logjam form and process"
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282:"Large in-stream wood studies: a call for common metrics"
545:"Structure and hydraulics of natural woody debris jams"
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433:The Ecology and Management of Wood in World Rivers
194:in Italy, where the dominant tree species is the
543:Manners, R.B.; Doyle, M.W.; Small, M.J. (2007).
383:"A legacy of absence: Wood removal in US rivers"
333:"A legacy of absence: Wood removal in US rivers"
114:Log jams are not to be confused with man-made
8:
518:Regulated Rivers: Research & Management
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568:
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737:10.1061/(ASCE)0733-9429(1995)121:4(341)
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799:Earth Surface Processes and Landforms
756:Earth Surface Processes and Landforms
287:Earth Surface Processes and Landforms
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752:"Plants as river system engineers"
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502:Canadian Broadcasting Corporation
495:Lamberink, Liny (26 April 2023).
725:Journal of Hydraulic Engineering
884:from the original on 2022-03-23
670:from the original on 2020-02-10
585:from the original on 2020-07-09
413:from the original on 2015-02-17
363:from the original on 2015-02-17
863:10.1016/j.geomorph.2011.11.011
387:Progress in Physical Geography
337:Progress in Physical Geography
134:Effects on river geomorphology
1:
710:10.1016/S0169-555X(02)00333-1
452:Geophysical Research Letters
261:1886 St. Croix River log jam
83:eruption of Mount St. Helens
175:Log jams provide important
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280:Wohl, Ellen (April 2010).
239:, a wooden dam created by
32:Logjam (computer security)
29:
549:Water Resources Research
399:10.1177/0309133314548091
349:10.1177/0309133314548091
206:In large rivers in the
878:"Definition of LOGJAM"
750:Gurnell, A.M. (2014).
625:10.1002/aqc.3270050206
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109:Northwest Territories
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848:. 139–140: 460–470.
638:Dixon, S.J. (2015).
570:10.1029/2006WR004910
473:10.1029/2022GL100913
458:(7): e2022GL100913.
381:Wohl, Ellen (2014).
331:Wohl, Ellen (2014).
854:2012Geomo.139..460C
811:2006ESPL...31.1558G
768:2014ESPL...39....4G
702:2003Geomo..51..141C
617:1995ACMFE...5..143G
561:2007WRR....43.6432M
464:2023GeoRL..5000913S
300:2010ESPL...35..618W
256:Stream restoration
215:Metaphorical usage
171:Effects on ecology
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67:large woody debris
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805:(12): 1558–1574.
208:Pacific Northwest
192:Tagliamento River
81:triggered by the
71:natural disasters
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116:timber rafts
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77:following a
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762:(1): 4–25.
142:Log jam in
118:created by
75:Spirit Lake
903:Categories
888:2022-04-30
674:2022-04-30
589:2022-04-30
417:2015-12-01
367:2015-12-01
267:References
246:Great Raft
237:Beaver dam
200:braid bars
157:deposition
90:Great Raft
47:Washington
827:129185856
664:131127480
579:129868907
482:258063526
407:131725942
357:131725942
124:log drive
98:Louisiana
94:Red River
79:landslide
882:Archived
784:55420478
668:Archived
583:Archived
435:: 21–47.
411:Archived
361:Archived
318:16337806
231:See also
106:Canada's
850:Bibcode
807:Bibcode
764:Bibcode
698:Bibcode
613:Bibcode
557:Bibcode
460:Bibcode
296:Bibcode
241:beavers
128:sawmill
120:loggers
92:on the
55:log jam
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181:salmon
18:Logjam
823:S2CID
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555:(6).
478:S2CID
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161:scour
126:to a
177:fish
152:flow
63:bank
59:wood
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