Posted by: waterworks | March 29, 2008

26. River restorers ♥ meanders

The phrase ‘river restoration’ describes an attempt to reverse-engineer a modified watercourse back to its imagined ‘natural’ state.  ‘Imagined’ is very much the operative word here, as photographic records rarely exist to provide aspiring restorers with a definitive goal.  Instead, they must apply a generic template, such as the Rosgen Classification of Natural Rivers.  This system suggests a number of channel form ‘archetypes’ that restorers can pick and choose from as they go about their intuitive work – a kind of fluviogeomorhphological salad bar. 

Now this is not necessarily always a good thing.  According to Professor Matt Kondolf (Berkeley), the Rosgen system unwittingly embraces a fetishism for European landscape design – notably a well-marked cultural preference for the meandering river form (as modelled so well by the Thames in her lower course, where she snakes from side to side in a well-defined and regal manner).  Working slavishly with Rosgen, the US restoration fraternity may be guilty of sometimes championing thoroughly inappropriate meandering restoration schemes for some American rivers.  In such cases, the restoration of a braided river channel – a branching, sinewy, badlands type of critter, all choked up on the mess of gravelly islands in its outlaw gut – could be a more appropriate management response than the (re)creation of an ersatz Thames. 

Citing the case of  Uvas Creek, California, Kondolf suggests that a lack of historical investigation – allied with a cultural leaning towards meandering on the part of the restorers – resulted in the wrong channel type becoming retro-fitted:  “A 0.9 km-reach of Uvas Creek, California, was reconstructed as a sinuous, meandering channel in November 1995.  In February 1996, this new channel washed out… Our historical geomorphological analysis showed that the reach had been braided historically, typical of streams draining the California Coast Ranges, with episodic flows and high sand and gravel transport.  After the project washed out, Uvas Creek re-established an irregular, braided sand-and-gravel channel… Our study casts doubt on several assumptions common in many stream restoration projects: … that a channel classification system is an easy, appropriate basis for channel design;  and that a new channel form can be imposed without addressing the processes that determine channel form.” 

 

Basically, it turns out that meanders get washed away if they’re put into the wrong places (the photographs above show the sad fate of the river restorers’ splendid new meanders after the first flood came). Read more about Rosgen here and more about Kondolf’s work here.

 

 

 

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  1. […] then so too are the trout. For this reason, river management schemes that do not protect or restore a variety of landforms-as-habitats are usually looked upon as something of a disappointment by […]


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