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Figure 18.1 The River Drau at Klelach-Lind, Austria. A) oblique aerial view October 2001, showing pre-restoration
condition: a single-thread channel with fixed banks. B) same view in June 2004, showing condition after bank
protection removed and side channel re-connected to main river flow, with banks actively eroding, channel aggrading,
and complexity increasing. From Habersack and Pi egay (2008), used by permission.
sees in presentations of stream restoration projects
in conferences attracting practitioners in North
America, where braided channels are typically
viewed with suspicion and the curved single-
thread, the stable channel in the left-side image
(Figure 18.1a) would be accepted implicitly as the
desirable goal. The main difference is that these
North American projects would utilize what are
termed 'natural materials' such as the root wads
of trees and boulders, rather than uniformly-sized
rocks, in order to stabilize the bank. Such stream
restoration projects are now required as mitigation
for development impacts in some parts of the
US, with a highly developed 'stream mitigation
banking' programme in North Carolina, which
requires construction of such single-thread stable
channels (Lave et al ., 2008; BenDor et al ., 2009).
Given that dynamic fluvial processes create the
complex habitats needed by native species, it
follows that the most effective restoration strategy
is to set aside a zone within which riverine
processes can function without conflicting with
human uses, termed variously the ' espace de liberte ',
'erodible corridor' (Pi egay et al ., 2005), 'fluvial
territory' (Ollero, 2010), or 'channel migration
zone' (Rapp and Abbe, 2003). This approach
can be viewed as not truly 'restoration' but
as 'preservation' of what is already working.
Nonetheless, it is probably a more effective use
of restoration funds than most projects involving
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