Dec 4, 2025
Week 11 – Salix, River Restoration and the “Bad Shed”
Where rivers learn to breathe again and neglected spaces remember how to live - exploring the quiet intelligence of bioengineering, soft infrastructures and unruly ecologies.
Technical
Reading rivers as living systems - flow, form and the shifting intelligence of water.
We began with an introduction to Salix River & Wetland Services, a company that specialises in river restoration, erosion control and the creation of wetland habitats. They work across rivers, reservoirs, coasts and marshes, usually where there are serious erosion problems or degraded habitats. Their whole approach is to replace or reduce hard engineering with soft, nature-based solutions, using vegetation, soil and water processes rather than concrete and rock armour wherever possible.
Mike explained that their work is grounded in three main drivers of river processes:
Hydrology – how much water is in the system, where it comes from and how flows vary over time
Geomorphology – how the river channel changes form, erodes and deposits sediment and evolves through meanders, braids and floodplains
Ecology – the plant and animal communities that occupy channels, banks and floodplains and how they respond to flow, substrate and disturbance
He stressed that successful restoration has to work with all three together, not just deal with erosion in isolation.
River form, process and scale
We looked at diagrams of river planforms and cross sections, tracing how rivers typically start as small headwater streams, then accumulate more flow, widen and become more sinuous as they move downstream. The talk covered:
Erosion on the outer banks of meanders
Deposition on inner bends, forming point bars
Vertical processes like incision and aggradation
The way rivers naturally migrate and cut off loops, creating oxbow lakes and complex floodplain habitats
This set up the argument that trying to “freeze” a river in place with rigid concrete channels often fights against these processes instead of working with them.
Problems with hard engineering
We then moved into a critique of hard engineered solutions such as concrete revetments, gabion baskets and large riprap. The issues Mike highlighted included:
High embodied carbon – emissions occur at every stage: extraction of aggregates, cement production, manufacturing and long-distance transport of heavy materials
Pollution from construction logistics – tyre wear particles, exhaust emissions and potential spillages as heavy trucks move materials to site
Downstream impacts on geomorphology – hard edges can speed up flows, leading to increased erosion and scour further downstream rather than solving the problem
Loss of habitat – armour layers replace natural bed gravels, silts and vegetated margins that would usually be used by invertebrates, fish, birds and mammals
Once in place, these systems often lock in a simplified channel form, with very little structural or habitat diversity
The key point was that traditional hard engineering might protect an asset in the short term but often degrades the river system as a whole and shifts risk somewhere else.
Crafting soft infrastructures - coir, bioengineering and the quiet architecture of repair.
Salix position themselves as a bioengineering company, using living systems and biodegradable products to stabilise banks and restore habitats. Their toolkit includes:
Coir rolls and coir pallets – cylinders and mats made from coconut fibre, often pre-planted with wetland species. These provide immediate erosion control and then transition into fully vegetated margins as roots knit into the bank.
Brushwood fascines (brush “weeds”) – bundles of woody material that slow down flow at the toe of a bank, trap sediment and create a base for vegetation to establish.
Biodegradable erosion control blankets and matting – jute, coir or other fibre mats that hold the soil surface in place on regraded banks while plants establish.
Hydroseeding – spraying seed, mulch and sometimes tackifier onto unstable or contaminated soils, for example metalliferous sites in Wales, to quickly establish vegetation that can bind the substrate and help immobilise heavy metals.
Mike gave examples of work in upland and mountainous catchments, where coir rolls and fascines are used to stabilise steep, flashy channels and in marsh environments, such as those in Thurrock, where the aim is to slow flows, encourage sediment deposition and rebuild vegetated fringes and saltmarsh.
From rivers to seabeds – Project Seagrass
Salix are also working in and around coastal and subtidal habitats, collaborating with organisations like Project Seagrass, which is dedicated to restoring seagrass meadows that have been heavily degraded by dredging, nutrient pollution and physical disturbance.
We discussed how seagrass:
Functions as a blue carbon store
Provides nursery grounds for fish and invertebrates
Stabilises sediments and improves water quality
The link here was that whether in rivers or shallow seas, many of the same principles apply: use vegetation and natural substrates to stabilise sediments and create habitat, rather than relying on hard, inert structures wherever possible.
Aquarock, rock mattresses and soft infrastructure
Mike then introduced Salix’s range of pre-filled rock products, which sit somewhere between hard and soft engineering. These include rock mattresses, rock rolls and AquaRockBags.
Key points:
These systems use smaller graded rock enclosed in robust nets, creating a flexible revetment with lots of interstitial spaces
The voids slow flow, dissipate energy and provide habitat for aquatic invertebrates and fish
Over time, fines and sediments accumulate within the voids and can become colonised by vegetation
We looked in more detail at AquaRockBags, which are used around bridge piers, along eroding banks, in scour pools and to protect undersea cables and pipelines. Salix emphasise that these can be:
Used as toe protection in deep water, with softer bioengineering solutions (coir, live willow planting, turf reinforcement mats) above water level
Deployed as temporary working platforms or access routes along sensitive banks during construction or maintenance, then left in place or removed as needed
Combined with live planting to create wicking zones where plant roots can colonise the stone matrix
The Yearls Weir case study in Cumbria was given as a key example, where AquaRockBags were used in scour pools in combination with root wads, live willow stakes and turf reinforcement mats to reinstate banks after major floods, while avoiding the ecological downsides of traditional riprap.
River Quaggy and urban restoration
A specific project that came up was the River Quaggy in Lewisham, where Salix supplied coir rolls and coir pallets to stabilise and revegetate the margins after the river was deculverted and brought back to the surface. The combination of bioengineering and re-naturalised channel form has created a more diverse urban river corridor with improved flood storage and public access.
This example tied back into our broader studio discussions about the value of “letting rivers breathe” in cities, rather than forcing them into narrow, hard-edged channels.
The potential of the ‘bad shed’ - biodiversity born from neglect, improvisation and the art of leaving things be.
The second half of the session shifted away from rivers and towards urban biodiversity, maintenance and neglected spaces, led by John Little, known for his work with the Grass Roof Company and community-led planting in housing estates.
John framed his talk around the idea of “the potential of the bad shed”. The “bad shed” is less about the actual structure and more of a metaphor for:
Unloved corners
Misused or fenced-off spaces
Scruffy edges around car parks, sheds or bin stores
Places that are not regularly mown, tidied or “managed to death”
These spaces often accumulate microclimates and niches – piles of rubble, dead wood, bare ground, shallow ponds or gaps in paving. Rather than seeing them as failures, John argued they can be some of the most important places for biodiversity.
Exemplars of messy richness – Canvey Wick, gravel pits and Great Dixter
John used several sites to illustrate how “rough” ground can be ecologically exceptional:
Canvey Wick, a former oil refinery site on the Thames Estuary in Essex, now a brownfield SSSI and one of the best sites in Britain for rare invertebrates, with over 3,200 species recorded.
A former gravel pit designated as an SSSI, where exposed substrates, standing water and varied topography support specialist invertebrates and pioneer plants
Great Dixter, which demonstrates how structurally and seasonally complex planting, combined with less rigid maintenance, can generate high insect diversity
The key message was that disturbance plus time plus heterogeneity often equals biodiversity. These landscapes are not neat, but they provide a mosaic of conditions that many species rely on.
Communities, gardeners and maintenance politics
A big part of John’s practice is about who maintains landscapes and how that shapes their ecological potential. Drawing on his work at estates like Clapton Park in Hackney, he stressed:
Gardeners and local residents are central to whether a scheme succeeds in the long term
Maintenance contracts that prioritise uniform lawns, frequent mowing and blanket herbicide use tend to erode biodiversity
Involving residents in design and decision making leads to spaces that are more loved, better used and more ecologically interesting
We discussed public attitudes to “messy” or less maintained spaces and the importance of “cues to care” – small signs of intent (paths, edges, explanatory signage) that help people understand that these are designed habitats, not neglect.
One of John’s more provocative examples was his use of dumped shopping trolleys in ponds, which quickly become submerged structures that create habitat complexity for invertebrates, amphibians and fish.
From there we moved to:
The ecological and social value of allotments as highly diverse, structurally complex and seasonally dynamic spaces
The idea that dead material – fallen branches, dead hedges, standing deadwood – is essential for many species and should be retained rather than tidied away
The use of recycled materials and poor substrates (crushed aggregate, sand, brick rubble) to mimic brownfield conditions that benefit ground nesting bees and other invertebrates
John’s own practice often uses Thanet sand or builders’ sand to create bare, free draining banks and mounds specifically for insects, especially solitary bees.
Green roofs, walls and the value of depth
We also spent time on green roofs and walls, which John and his company have been working with for years. The important technical point he emphasised was that if we are serious about biodiversity, then:
Green roofs need a minimum of around 150 mm of growing medium
Deeper, more varied substrates support a wider range of plants, invertebrates and microhabitats than thin sedum mats
Using recycled aggregates and sand on roofs can replicate the conditions found in biodiverse brownfields, rather than just creating a uniform carpet of sedum
We linked this to earlier weeks on construction build ups and drainage and to wider conversations about how roofs and walls can act as extensions of ground-level habitats, not just decorative “eco” tokens.
Reflection:
This week brought together technical river engineering and informal urban ecology in a way that felt very relevant to my studio work.
From Salix and Mike Yates, I took away:
The importance of thinking in terms of process rather than just form – hydrology, geomorphology and ecology as a combined system
A clearer understanding of bioengineering components – coir rolls, fascines, biodegradable mats, hydroseeding and rock-based systems – and how they can be layered vertically from river bed to bank top
A more critical view of hard engineering, especially in terms of embodied carbon and downstream impacts
From John Little, I took away:
A stronger appreciation of the ecological value of roughness, mess and neglect
How community involvement and maintenance contracts can either support or completely undermine ecological design intentions
Practical examples of using dead material, poor substrates and improvised structures to create microhabitat and support invertebrate life
For my own projects, especially those dealing with rivers, marsh edges and urban brownfield-type sites, this session reinforced the idea that restoration and design are as much about letting processes happen as they are about drawing lines on a plan. It also reminded me that small, overlooked details – a patch of bare sand, a rotting log, a “bad shed” – can be as important as grand design gestures in shaping biodiversity and lived experience of a site.