{"id":4132,"date":"2012-01-15T23:09:23","date_gmt":"2012-01-15T23:09:23","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=4132"},"modified":"2012-01-15T23:09:23","modified_gmt":"2012-01-15T23:09:23","slug":"landslides-and-logging-an-pictorial-example-from-new-zealand","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2012\/01\/15\/landslides-and-logging-an-pictorial-example-from-new-zealand\/","title":{"rendered":"Landslides and logging – an pictorial example from New Zealand"},"content":{"rendered":"

As I was driving across from Nelson to Picton in New Zealand yesterday (in quite glorious weather), I came across this recently logged and replanted slope:<\/p>\n

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This is a nice example of the way that logging causes a short-term landslide problem.\u00a0 It should be clear from the picture above that the logged areas have suffered significant shallow landsliding, whilst the upper, still forested, slopes are much more stable.\u00a0 In a couple of places the landslides are quite interesting.\u00a0 The largest appears to be this complex on the lower right side:<\/p>\n

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This complex is actually several (I think about ten) very small slips that have each entrained material and then entered the drainage line.\u00a0 As a result the amount of debris at the toe of the slope is quite large.\u00a0 This illustrates two major problems with deforestation.\u00a0 First, when trees are present these small slips are much less likely (the strength accorded by roots is enough to prevent themfrom starting, for example). Second, trees prevent small slips from entraining debris from the slopes below, and from entering the drainage line.<\/p>\n

It is also interesting to note that several of the other small landslides in this picture started just above the tracks, where the slopes have been cut to create the road bench.\u00a0 This is very common, and indeed was a key factor in the devastating Sarno landslides in Italy in 1998<\/a>, which killed about 150 people.<\/p>\n

Another interesting landslide is on the left side of the slope:<\/p>\n

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This slip appears to have initiated at the bottom of a natural topographic hollow.\u00a0 Imagine what happens in heavy rainfall with the original trees missing – the water flowing across the surface and through the soil will be focused into this area, allowing a small landslide to start.\u00a0 Again a comparatively small slide has then turned into quite a large event as it has entrained material downslope.\u00a0 This also illustrates the difficulty of restabilising a slope that has started to slip.\u00a0 Planting trees is often touted as the simple solution, but stabilising the soil long enough for trees to take root and start to strengthen the soil can be a real problem.\u00a0 Nature gets around this problem through a vegetation succession (the slip above has started to be colonised by small plants and shrubs), but this can be a slow process. Humans often want or need to act much more quickly.<\/p>\n","protected":false},"excerpt":{"rendered":"

Some pictures of landslides triggered on a slope after logging, taken in New Zealand yesterday<\/p>\n","protected":false},"author":22,"featured_media":4134,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[598],"tags":[469,599,959,7,208],"class_list":["post-4132","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-landslide-processes","tag-featured","tag-foorest","tag-landslide-report","tag-new-zealand","tag-shallow-landslide"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/4132","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/comments?post=4132"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/4132\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/4134"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=4132"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=4132"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=4132"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}