Soil mass movement – why management isolated from science is a bad idea

Soaking rain this week has been welcomed by all, particularly frogs. However, there was another ‘rock fall’ on Clyde Mountain that, although small, managed to break through the new retaining fence and temporarily block the highway.

Across the Pacific in Washington state, a massive ‘landslide’ engulfed part of the small town of Oso, killing up to 90 people.The landslide blocked the river it crossed, flooding upstream properties, and one expects, heavily polluting water heading downstream.

A 2009 report, produced by the Washington Department on Natural Resources, examined 25 of 1,400 landslides across state in the same year.

The authors suggest ” . . . the main factor triggering a landslide is a significant natural disturbance such as a large magnitude precipitation event or earthquake. Other factors, including topography, geology, reduction of material strength over time due to weathering and land use history can predispose a site to slope failure and contribute to instability.”

Reasons behind reducing material strength over time aren’t provided, so it maybe the Washington DNR, like the NSW Forestry corporation, are not required to consider soil chemistry.

Mass movement 2135

As indicated in the harvesting plan map above, what is described as a ‘stabilised’ area of mass movement was located in Cpt 2135. I’m not sure how far they got with this logging, before it was found to be illegal and suspended, but it is a good example of what the regulators are prepared to licence. FCNSW proposed logging above and around the area, as well as clear two log dumps and construct three stream crossings below it.

Much of this was made possible by private landholders, enabling FCNSW access to the areas through their land. While it could be argued, should soil materials on the very steep slopes move downhill, the private landholders bear some responsibility. The bigger question would seem to be whether the decision to risk potential downstream degradation with reckless management, should be left solely to FCSW and the regulators.

In that regard, and as FCNSW’s Mr Tuan is yet to provide a response to recent correspondence, I sent copies to O&H Regional manager Mr Michael Saxon, to keep him abreast of developments, and suggesting the NPWS also provided incorrect information. Mr Saxon responded with ” . . to my knowledge NPWS/OEH had no input into the assessment report that Daniel Tuan refers to.”

Among other things the 2002 assessment suggests “Project Manager has chosen to ignore the expert advice of NPWS, RLPB and DLWC.” and “Proponent appears to be working in isolation of other koala recovery projects in the region ( eg. current NPWS/EPA funded recovery project)”.

I advised Mr Saxon that koala recovery officer Chris Allen had refused to support the koala nomination and the project. Also, that developments since that time would seem to confirm the soil science on which the project is based, and the community concerns about forest health, it is intended to address, remain isolated from other koala recovery projects.


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