Way back in one of the lockdowns at the start of the COVID-19 pandemic, online training courses became incredibly popular. A number of UK-based river-menders, including my Wild Trout Trust colleague Tim Jacklin and I, braved virtual jet-lag by attending a week-long remote learning programme provided by Utah State University in the USA.
Above image: Published by Utah State University: the LTPBRR Pocket Field Guide
This course was a rapid induction into the theory and practical applications of a super-simple idea called ‘Low Tech Process Based River Restoration’ (LTPBRR) – essentially, mimicking the ecological benefits of natural tree fall (as well as wood introduced by keystone species such as beavers) by adding and retaining large amounts of wood in river channels.
Why River Restoration Matters
Healthy rivers rely on a ‘three-legged stool’ of contributing factors: water that’s clean, as well as flowing in sufficient quantity, and finally complex habitat structure, often in the form of natural wood. Together, all of these facilitate natural processes, such as swifter currents scouring away silt from spawning gravels, which in the end make a comfortable home for innumerable species including wild trout.
Sadly, many rivers in the UK, Europe and America have been functionally ‘starved’ of their vital supply of wood, often as a result of over-zealous flood risk management in the past. So LTPBRR suggests adding accumulations of this wood back into the river, in places where it’s likely to produce the most benefits – and may also teach us how to ‘force’ natural processes even more effectively in the future. (Importantly for anglers, all those extra woody features will also provide more lies for trout to occupy, and thus more targets for our flies!)
Since that online course, several Wild Trout Trust colleagues have been looking out for suitable locations to try LTPBRR ideas in the UK, ideally in the form of ‘beaver dam analogues’ (BDAs) and semi-fixed ‘Post Assisted Log Structures’ (PALS), which we’d stabilise with wooden stakes whilst minimising more traditional wire and cable fixings. BDAs are structures which are designed to span the whole width of the channel, so as to push higher flows out into the floodplain like real beaver dams – whereas PALS use wooden posts to stop smaller logjams and tangles of branches from floating away in the next spate.
In the end, my teammate Tim Jacklin got there first, with a project on the upper Witham in Lincolnshire. Here’s his account of the project:
‘The site in question is a 600m reach of river that the Wild Trout Trust was involved in restoring back in 2015, when the river was realigned to bypass a weir and restore its natural course. This project restarted natural river processes, including floodplain connectivity, but an unforeseen issue was the lack of supply and retention of gravels within the channel. The woody structures are intended to help by taking the sting out of high flows, pushing water onto the floodplain earlier, and creating more depositional areas for gravel.
A number of different designs were tried, based on the freely available guidance on ‘Low Tech Process Based River Restoration’ published by Utah State University. Live willow was incorporated with the aim of literally giving root to the structures and prolonging their lifespan. And it’s been interesting to see how they have (and haven’t!) weathered subsequent storms, including by far the highest flows ever recorded on the upper Witham in January 2025.
Thus far, our assessment of these structures is that they provide excellent benefits for river habitats and natural processes. However, as dynamic features, they may also have a limited lifespan (often quite short) if they’re not augmented by humans, beavers or more wood drifting down from sources upstream.’
One of the key messages from the LTPBRR course that Tim and I attended was that the river may need to be ‘fed’ regularly with more wood – especially if it really lacked any before – whilst accepting that some of the wood in our structures may quickly get swept away downstream.
So, while woody LTPBRR structures like these can certainly help our rivers by adding instant complex habitat, we’ll also need to implement nationwide programmes of planting more woodlands in thick buffer strips alongside our rivers. We’ll then need to allow those trees to mature, so that they can provide shade for the rivers in our warming world, as well as nutrient-rich leaf litter, and finally fallen timber for the river to chew on.
Meanwhile, one of the Wild Trout Trust’s founders, Charles Rangeley-Wilson (who’s now working on restoring chalk streams in Norfolk) says he’s more and more convinced that ‘entire riparian trees, felled or better still pushed in with their root plates’ will do the best job of enlivening flow and providing more varied habitat for animals and plants. ‘The largest possible units of large woody material are the way to go!’ he recently said on Instagram.
Maybe that’s really the ultimate in LTPBRR?
Best of all, there’s no doubt that more, and bigger, trout will live happily among these tangles of fallen wood. So maybe we’ll also need to get more adept at casting to them there (and not mind losing a few flies in the process!)
To find out more about Low Tech Process Based River Restoration, visit lowtechpbr.restoration.usu.edu
If you manage a stretch of river which might be suitable for further trials of LTPBRR in the UK, contact the Wild Trout Trust for an Advisory Visit and we’ll see what we can do to help!
