Posted on January 30, 2014
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Posted on January 30, 2014
Posted on January 08, 2014
Perhaps topical given current examples of river-bed-transporting extreme flows happening in many parts of UK...
In a striking similarity to the widespread lack of understanding of the impacts of dredging on flood risk - the problems caused by weirs that choke off the downstream progression of river gravels, cobbles, sands etc. are not widely appreciated.
The presentation below gives a basic outlining of why everything that lives in our rivers depends on the capacity for river channels to continually transport (and periodically deposit) river bed material from the hilltops to the sea. If we work better with (rather than against) these processes it would be far better for both societal needs/costs and the natural world.
Posted on January 02, 2014
Posted on December 14, 2013
Posted on October 29, 2013
Posted on October 23, 2013
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-bed material. Each of the different diameters of gravels/cobbles/boulders that come from eroded banks form a unique and vital habitat either for particular species or particular stages within the lifecycle of a species.
So the optimum for biodiversity (and, consequently...
Posted on October 07, 2013
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 erosion in upstream reaches.
It also rapidly leads to the re-filling of the dug-out channel... (back to square one, so you dredge again....)
The other major/worrying effect is the interruption of the transport of sediment downstream of the dredged reach. Whilst the bed material is being re-accumulated in...
Posted on September 19, 2013
The Wild Trout Trust very gratefully benefited from the generous loan of Severn Rivers Trust's "Emriver" at this year's CLA gamefair. As well as proving to be a great way to engage game fair attendees of all ages, it provided a fantastic opportunity to accurately simulate many scenarios that we routinely encounter in our river habitat works. This first video introduces some of the basics - and shows the effect of two common habitat installation techniques: marginal brash and log flow-deflectors.
There will be a series of short videos that follow this first introductory piece. Each subsequent film will look at specific scenarios and model their outcomes - which are often highly unexpected unless you have quite a lot of existing experience with geomorphology...
Posted on July 23, 2013
Posted on July 08, 2013
Shaun Leonard gave a huge amount of masterclass training over both days of the Urban Conclave - enabling attendees to benefit from just a small part of his extensive experience in decoding the secrets of the lives (and sometimes deaths) of fish just using visual examination of small samples under a microscope.
Combining the Trout in the Town friendly competition monitoring methods with training in scale sampling (which does not harm the fish)provides anyone who cares about an urban (or rural!) river with a wonderful tool for understanding the fish populations in their river.
For instance, the picture at the top of this blog entry gives a clue to why one of the most commonly-heard myths about taking large fish for the table is completely wrong...
Just by way of explanation, the picture shows a trout scale under a microscope. The scale was taken from the fish (caught and released by the WTT's Gareth Pedley from the river Tweed) in the photograph below:
Although they are not like the rings in a tree trunk (i.e. one band for each year!) you can still often see periods of time where the growth is slower - and the groups of multiple...
Posted on July 02, 2013
Another of the MANY great talks that the participants in the 2013 Urban River Champions Conclave benefited from was Professor Lerner's account of how the Aire Rivers Trust has set up the plan for the restoration of Bradford Beck.
I felt that it was important to set up the whole Conclave by bracketing the subject of Resilience with two talks; the first of which was Phil Sheridan's deeply personal and incredibly inspirational dissection of the qualities of resilience that we encounter (and require) during each of our "lived experiences". The second key talk was very deliberately designed to expose the bare nuts and bolts of a highly structured series of practical solutions to many of the problems that Trout in the Town groups routinely encounter. In other words, the second talk offered one possible "route map" of how to turn the inspiration and personal resilience identified and instilled by Phil's talk into a series of effective an efficient actions.
This second "bracketing" talk was, of course, Professor Lerner's presentation. I've reproduced it in the video below so that both of the absolutely key expert presentations from the 2013 event are available as a reminder for the Conclave attendees - as well as...
Posted on July 01, 2013
Posted on June 28, 2013
I'll sandwich this quick-fire montage that captures some of what went on at May's Urban Conclave weekend between Phil Sheridan's full presentation (blogged previously here: http://urbantrout.blogspot.co.uk/2013/06/urban-conclave-if-youve-ever-felt.html)and a future blog post featuring Prof. David Lerner's excellent talk (video edit still on the "to do" list...).
There were many more fantastic talks that I was unable to video unfortunately (and I only chose to film the presentations by people who I absolutely knew wouldn't be fazed by the camera pointed at them!)
The video embedded below documents the meeting of around 25 core members who run Urban River restoration projects from around the UK including: Wales (Rivers Taff and Ogmore), Salford, Sheffield, Newbury, Burnley, London, Huddersfield, Bradford, Keighley and Wigan.
It was an honour to host them all and to hear all of their reports, stories, trials and tribulations. I also believe that the weekend was truly inspirational for all participants - a vital factor given the many set-backs and nay-sayers that every person who runs a project like these will encounter time and again. I also look forward to the next time we run this event - as there were several groups who were unable to attend on the specific date of the...
Posted on June 27, 2013
Posted on June 26, 2013
Here is a short video that was part of a talk that Mike Clough invited me to give at the conference launching "INNSA" (http://www.innsa.org/). I've added some explanatory voiceover - in place of me talking and pointing at the screen in person :)
The clip explains why invasive plants that die back in winter cause huge increases in "wash-load" sediments (i.e. sediment that is washed into the river from the surrounding land - rather than derived from existing river-bed material).
When you realise that this can bury and suffocate spawning beds, the problem becomes much more obvious than the situation you see in high summer (when growth is lush). The loss of large areas of spawning beds has the potential to be far more serious in terms of reducing the population of fish in your river than occasional (and still serious) poaching. It is just that the fish impacted by silt accumulation never had a chance at life in order to become large enough to be visible victims (unlike poached adult fish).
I know lots of anglers who would be outraged by people illegally netting their rivers, but who "kind of know that invasive plants are not ideal" - but are maybe...