{"id":6947,"date":"2011-11-12T08:15:34","date_gmt":"2011-11-12T13:15:34","guid":{"rendered":"http:\/\/all-geo.org\/highlyallochthonous\/?p=6947"},"modified":"2011-11-12T00:23:13","modified_gmt":"2011-11-12T05:23:13","slug":"scenic-saturday-wood-in-streams","status":"publish","type":"post","link":"https:\/\/all-geo.org\/highlyallochthonous\/2011\/11\/scenic-saturday-wood-in-streams\/","title":{"rendered":"Scenic Saturday: Wood in Streams"},"content":{"rendered":"

\"A<\/span>One of our field trips in my Fluvial Processes class takes the students to the lower reaches of Mallard Creek, the urban stream that drains the northern portion of Charlotte, including our campus. For most of its length, Mallard Creek is highly incised, so it’s quite a surprise to see the stream near its mouth, where it is more free to meander through a floodplain forest. For their field exercise, the students measure meander geometry and plot it against the classic Leopold, Wolman and Miller<\/a> relationships, they attempt to identify bankfull channel geometry, and they contemplate the effects of wood on channel morphology.<\/p>\n

\"Looking<\/a>

Looking upstream at one of the big wood jams in Mallard Creek, near Harrisburg, North Carolina<\/p><\/div>\n

\"Looking<\/a>

Looking downstream at the same wood jam as above. Notice how much smaller wood (and trash) has piled up against the big keystone logs.<\/p><\/div>\n

Wood is perhaps the most striking feature of this reach of Mallard Creek, because it is everywhere, and because it is profoundly shaping the channel geometry and meandering behavior. So it is appropriate that Mallard Creek had an important role in the scientific recognition of the importance of wood in shaping fluvial systems. A 1979 article by Ed Keller and Fred Swanson, “Effects of large organic material on channel form and fluvial processes<\/a>“, is the fifth most cited paper in geomorphology, according to an analysis done by Martin Doyle and Jason Julian<\/a> in 2005. As part of their analysis, they asked the authors of the highly cited papers to speak to what inspired the work. Here’s what Keller said: <\/p>\n

I first recognized the importance of large woody
\ndebris while doing PhD work on pools and riffles in
\nWildcat Creek near Lafayette, Indiana in 1971. I observed
\nthat the debris formed a jam that backed up
\nwater at high flow. The backwater caused a chute to
\nform across a bend, facilitating a meander cutoff. I
\nnearly forgot this until starting as a new Assistant
\nProfessor at the University of North Carolina at Charlotte.
\nI was looking at Mallard Creek near the university
\nfor a site to study pools and riffles. The floodplain
\nwas forested, and I was complaining to myself that I
\ncouldn\u2019t find a \u201cnatural\u201d site without large woody
\ndebris interfering with the morphology I was looking
\nfor. Then it happened\u2014I heard a large groan followed
\nby a loud cracking. I walked around a bend just in time
\nto see a large tree fall into the stream with a great
\nsplash! I suddenly had the a-ha\u2013this is \u201cnatural\u201d\u2013these
\nstreams with forested floodplains and lots of trees on
\nthe banks are greatly modified by large woody debris
\nthat enters the active channel! Then in 1973, I moved
\nto the University of California, Santa Barbara, and
\nstarted work in the redwood forest of northwestern
\nCalifornia where the woody debris that ends up in
\nstreams is truly gigantic. I contacted Fred Swanson,
\nwho was working for a US Forest Service Research
\nLaboratory at Oregon State University, and suggested
\nwe write a paper on the role of large woody debris on
\nstream channel form and process. Fred had been working
\nfor several years on large woody debris in streams
\nof the Oregon Coast Ranges. We had a great collaboration
\nat just the right time for the emerging field of
\nforest geomorphology. <\/p><\/blockquote>\n

I haven’t seen a tree fall into Mallard Creek, but in the five years I’ve been bringing my class to this site, I’ve seen some pretty remarkable changes. The photos below show a meander that cut off sometime between May 2010 and October 2011. In May 2010, the “new” channel (on the left) existed but was very narrow and didn’t carry water at low flow. Now, the “old” channel (on the right) is largely sedimented (and wood-jammed) in and carries only a trickle of water at low flow. While the meander would likely have cut off at some point in the future, my interpretation is that a series of large wood jams in the old channel backed up water during high flows, increasing overbank flooding, and greatly accelerating the cut off process.<\/p>\n

\"Old<\/a>

A recently cutoff meander in Mallard Creek. The new channel is to the left, the old channel (active in May 2010) flowed to the right.<\/p><\/div>\n

\"Looking<\/a>

Looking down the old channel, from atop the large wood at the cutoff point.<\/p><\/div>\n

\"Looking<\/a>

Looking down the new channel, with students for scale. The students on land are on an island between the old and new channels.<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

One of our field trips in my Fluvial Processes class takes the students to the lower reaches of Mallard Creek, the urban stream that drains the northern portion of Charlotte, including our campus. For most of its length, Mallard Creek … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[46,22,144,26,14,155],"tags":[151,157,162,214,527],"class_list":["post-6947","post","type-post","status-publish","format-standard","hentry","category-by-anne","category-environment","category-geomorphology","category-photos","category-publication","category-science-education","tag-erosion","tag-fluvial-geomorphology","tag-meandering-rivers","tag-rivers","tag-wood-in-streams"],"_links":{"self":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/6947","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/comments?post=6947"}],"version-history":[{"count":4,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/6947\/revisions"}],"predecessor-version":[{"id":6953,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/6947\/revisions\/6953"}],"wp:attachment":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/media?parent=6947"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/categories?post=6947"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/tags?post=6947"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}