Skip to main content

Posts

Showing posts from October, 2013

Shipley Weir

Had a great visit to and discussion around Shipley weir recently. Stephen Bottoms (who organised it all) has done a great blog post here. Also, do go and check out the rest of the "multi-story-shipley" website. It is great and a perfect example of a central theme to the Trout in the Town project - local communities' relationships with their urban waterways:

http://multi-story-shipley.co.uk/?p=718

You'll find explanatory text on the site about Stephen's great short film (below) on Bradford Beck...a stream we've featured a few times on the Trout in the Town Blog and you can use the search function to find those too :)

Bank erosion - a matter of balance

You can always have too much or too little of a good thing. When it comes to revetments (re-inforcements) of river-banks; there are a whole host of pitfalls.



On the one hand, many sections of river suffer from excessive grazing of the land surrounding them that leads to a dramatic reduction in the variety of bugs, plants as well as fish populations that can be supported. In addition, many rivers that run through towns and cities often pass through quite intensively used land upstream of urban reaches. The excessive inputs of fine silt and sand where bank-erosion is rampant and extensive often end up being accumulated in the engineered sections of channels in towns and cities. As well as causing maintenance problems,this can smother what may, otherwise, be perfectly good spawning gravel.

Conversely, where efforts to "lock" a river channel in one place are over-zealous; the result will be the strangulation of supply of spawning gravels and a variety of cobbles and other river…

Unintended de-stabilising consequences of dredging...

The WTT borrowed the fabulous Emriver kit from Severn Rivers Trust during the 2013 CLA gamefair. It allowed us to set up a whole range of common river-channel scenarios in an accurate scaled-down simulation. Dredging was one of the things we modelled:

Dredging river-bed material is something that is of particular relevance to the urban/heavily-modified channel environment. As is so often the case with rivers, what seems like the obvious and correct thing to do can actually blow up in your face (or someone else's face several miles up or downstream!).

Just as intriguing are the potential knock-on impacts of ad-hoc dredging in rural environments in an effort to increase the capacity to drain land...

Nature abhors a vacuum and removing accumulated material from a river channel can have far-reaching and unintended consequences. The first principle effect is to increase the demand for eroded river-bed and river-bank material from upstream. This can dramatically increase the rate of ero…