Trout in the Town Blog

20/05/2014 - 16:25

In just one of many illustrative examples in his book "Antifragile - things that gain from disorder" author Nassim Taleb talks about the irony of sports-shoe makers touting that their most advanced models are those that most closely replicate the bare human foot. This is fascinating since it highlights that attempting to smooth out and cushion the shocks experienced during running actually had the effect of massively increasing muscular and skeletal injuries from running.

In barefoot running, the toes and arches of the feet act as shock absorbers and - crucially - allows them to be exposed to the action of running that actually strengthens them in this function. By contrast, the attempt to eliminate those specific stresses resulted in humans striking the floor with their heels rather than their toes and the additional padding robbed our feet of the varied "training" that prevents things like fallen arches and plantar fasciitus.

Another example favoured by Nassim Taleb is that of "regulators"; devices that were fitted to smooth out some of the slightly erratic running of steam engines. The idea was to make them more efficient - and for much of the time this is the effect that they had. However, on the odd occasion, the regulators would get locked in to destructive cycles of inappropriate corrections - and cause the engine to run disastrously/explosively out of control!

In fact, Taleb's book compiles a fat list of examples in which an attempt to rid systems of the natural variability (or in his words "sucking randomness out to the last drop") results in periods of apparent comfort and stability - followed by catastrophic "blow up" or "extinction" events. Those examples are drawn from an impressive array of (seemingly) totally unrelated domains from finance (stock market crashes), through parenting (minor scrapes and bruises are good for kids' development), to careers (a position in a large corporation seems more stable than being a cab driver with variable fares - right up until the corporation makes you redundant).

For me - his writings on these attempts to smooth out randomness which result in periods of stability followed by catastrophe chime very much with lots of efforts to manage flood risk by modifying river channels. There is a certain appeal to the thought that by smoothing and speeding the flow of water out to sea,the risk of it spilling out of its banks should be reduced. But is that a safe assumption to make in the built environment?? In practice that assumption can prove to be catastrophically misplaced. For instance Robert E. Criss and Everett L. Shock's paper "Flood enhancement through flood control" Geology, October, 2001, v. 29, p. 875-878 attributes the increased flooding magnitude and frequency to the engineered channelization that was designed to smooth out and reduce the threat from flooding.

Similarly, I am keen to highlight at any given opportunity the potential responses of river channels when they are dredged to produce dimensions over and above the capacity established through natural erosion and deposition processes:

Essentially - in common with financial markets and steam engine regulators - there are often hidden downsides to naive interventions in the movement of floodwater through a catchment. Those hidden downsides are generally large enough to wipe out (by many, many times over) any benefits that may have accrued during the period of relative (and illusory) stability...Again, this is true of financial trading just as much as it is true of counter-terrorism or - indeed - efforts to increase and smooth floodwater conveyance upstream of hydraulic bottlenecks...

Daniel Kahneman writes (for example in his book "Thinking, Fast and Slow) with consumate persuasiveness and good sense on how we, as humans, are predisposed to defaulting to belief in representations of the world that consist of a simple story. In fact, we are far more likely to believe something that we can form into a simple narrative than an opposing view backed up by hard, objective evidence. Consequently, we treat sharks as more dangerous than traffic - despite what we know about road death and shark attack statistics...

Professor Kahneman uses the phrase "cognitive ease" to describe the state in which we readily accept notions so long as our brains can construct some kind of story around them. It is this state that makes us extremely vulnerable to errors in reasoning (or cognitive traps) - as illustrated by the fact that we will always feel that a 90% fat free yoghurt has to be much healthier than a yoghurt advertised under the tag-line "10% of this product is pure fat". In the same way, we find it nearly impossible (unless we really force ourselves to sit down and think about it) to resist the following cognitive trap - which came to be known as "The Linda Problem":

Participants in the experiment were told about an imaginary young woman named Linda, who is single, outspoken and very bright, and who, as a student, was deeply concerned with issues of discrimination and social justice. The participants were then asked which was more probable: (1) Linda is a bank teller. Or (2) Linda is a bank teller and is active in the feminist movement.”

The overwhelming response was that (2) was more probable; in other words, that given the background information furnished, “feminist bank teller” was more likely than “bank teller. However - this cannot possibly be true; every single feminist bank teller is (of course) a bank teller - but there are lots of additional bank tellers that will not be active feminists. It is the same as saying "Linda is a red haired bank teller" is more likely than the statement "Linda is a bank teller who could have any hair colour".

Turning our attention to the prominent (and dreadful) recent impacts of flooding in the Somerset Levels. These events took a serious toll on the lives and livelihoods of residents - with particularly arduous circumstances being endured by those members of the farming community based on land that was inundated for the longest periods of time. However, surely we should not fall into a known cognitive trap that makes an easy soundbite - but actually completely ignores the true situation? Aren't we at risk of selling those communities at risk of flooding short by offering purely cosmetic activities?

The sound-bite of "we must dredge the rivers" so that the flood water can be taken away intuitively makes sense - and it has been readily accepted (and campaigned for). But could this be just another version of the Linda problem? Might we be accepting the simple story that we can construct in our own minds instead of taking the tough look at the complex and unpalatable evidence at hand? Consider the following, provable, facts:


  • It would be impossible to dredge the rivers to a capacity that would accommodate the volume of water that flooded such a vast area of land
  • The limited "hydraulic gradient" imposed by the low-lying land (especially at high tide) significantly limits the rate at which water will run out to sea

In other words, it doesn't matter how many lanes you add to a motorway if there is still a road block at the far end...

All of which brings us right back round to Nassim Taleb and his writings on the concept of fragility. You see, Mr. Taleb - far from being an economic boffin with no connection to the real world - actually puts his money where his mouth is. He has amassed a (considerable) income by adopting a particular philosophy as a financial trader. His approach could be summed up in part by the following thought experiment:

It does not matter that you cannot predict which specific lorry (on which specific day) will destroy a weak bridge; it is just important to know that the bridge is fragile.

By identifying those commodities and institutions that are fragile to catastrophic blow-ups, it can be possible to insulate yourself from the negative consequences of such an (inevitable - but unpredictable in time) event. Moreover, it is actually possible to bet against such fragile institutions! This is how Taleb not only survived, but actively profited from the stock market collapse of 1987. He also correctly predicted that the credit crunch (and ongoing associated recession) was an inevitable consequence of the activities of big banking...

So, here is what we know about the significant (but obscure) downsides of trying naively and too aggressively to remove randomness to produce predictable stability within a chaotic system (such as flood water conveyance by channel modification): periods of apparent stability are followed by a catastrophic event of much greater magnitude...

Furthermore, we already realise that it is not really that important to know when a catastrophe will strike. Instead it is important to know whether we are fragile to the effects of that catastrophe when it does strike. Is the bridge strong or weak??

We KNOW that building and living in the floodplain will be, from time to time, fragile to unusually high rainfall, falling on especially impervious and steep surfaces that run into low-lying land where the tides can prevent the escape of that spectacular rainfall. It is not a consequence of insufficient intervention into the size and shape of the river channels - it is an inescapable feature of flood plains. Consequently, no measure (regardless of how expensive) can be put in place that will eliminate this risk and that fragility. However, it is interesting to note that one of the corners of Somerset that did NOT experience catastrophic flooding last summer was the areas in which some of the natural variability of water escaping onto the floodplains had been re-instated...

Dredging upstream of a "roadblock" reduces flood risk?
Linda is more likely to be a feminist bank-teller?


12/05/2014 - 15:25

Some readers may have already seen the various pieces that I've contributed on managing surface water in urban and rural catchments (e.g. videos embedded at the bottom of this post) alongside the organisational role to Sheffield's first One Big River event. This was a week of activities focused on the rivers of the Steel City and was timed to coincide with both the River Restoration Centre's Annual Conference (held for the first time at Sheffield Hallam University) as well as the formal signing (and Cabinet adoption) of the Waterways Strategy.

The various community and volunteer events that formed the week-long programme ( included a family-day of riverside events run by the Sheffield branch of the Trout in the Town project (SPRITE) and the Wild Trout Trust. Everyone involved really enjoyed talking to local residents and visitors and showing them the life that abounds in the river via both bug sampling displays and also a demonstration of the "Mayfly in the Classroom" apparatus. This also provided an excellent opportunity to hand out the materials containing contact details and descriptions of SPRITE's monthly activities to people who have been living close to the patch of river corridor that the group looks after - but who had not yet heard of all the good things that are done by these dedicated volunteers.

Unfortunately, the downpours in the run up to the SPRITE/WTT event meant that the planned water crowfoot planting was not safe to carry out - so this will be rescheduled for more appropriate conditions. However, there was ample opportunity to introduce some newcomers to the activity of fly fishing (of both British and Japanese varieties!) in the park where our Gazebo of displays and information was installed for the day.

I hope that we can run a similar event next year and, in the meantime, please check out the collated information on this inaugural event on all the web pages here:

Also, please have a look at the important and surprising information about managing surface water for the benefit of society and wildlife:

17/04/2014 - 10:51

Wildlife photographer and videographer Jack Perks visited Sheffield yesterday as part of his bid to document as many of Britain's freshwater fish species as he can. Some of these species face an uncertain or bleak future - and Jack's project ( could be the last time that they are possible to document on film. On this, his first recce visit, I took Jack on a whistle-stop tour of a number of locations spread across the city; ranging from retail/city-centre areas, heavy industry zones and suburban sites. Jack's VLOG gives a snapshot of his visit below:


19/02/2014 - 18:46

Valuable proof that anglers and community interest groups can be taken seriously by large companies (as well as government bodies) was ably demonstrated yesterday during a meeting convened by the formidable Mike Duddy of Salford Friendly Anglers (centre of picture above).

Discussions over the current (and future-planned) status of a range of Combined Sewer Outfalls on the Irwell system were held at Mike's offices in Salford. Presentations by network managers and external affairs representatives of United Utilities (the local water supply company) were combined with debate over conditions in and around the river.

I'm pleased to have been able to support the group in getting to the stage in the discussions through some assistance in data crunching and interpretation that allowed the "priority" discharges affecting their rivers to be identified based on reported chemical discharge information. Coupled with detailed local knowledge from anglers such as Arthur Hamer on the observed performance of outfalls - a useful exchange of information occurred; enabling plans for exploring collaboration and partnership efforts for the benefit of the condition of Greater Manchester rivers to be made.

Great stuff - and an inspiration to all who may feel intimidated or unable to contact and influence large institutions on the issues that matter in their environment
30/01/2014 - 09:32
Nice brief profile video on this link

Support Salford Friendly Anglers to keep the recovery going,
08/01/2014 - 14:12

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.

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