Repairing eroded banks using natural materials

By Dealing with litter and fly-tipping in local brooks
Comments 35
17 Jul 2026

Repairing eroded banks using natural materials

Why banks erode — and when to step in

Most small watercourses in Britain have been straightened, deepened or cleared at some point, and many are now wider and deeper than they want to be. When a brook is over-wide, the flow loses energy and drops its sediment, but the banks take the brunt of every spate. Add livestock trampling, the loss of bankside trees and the flashy runoff from drained fields and hard surfaces, and you get the undercut, crumbling edges so familiar on lowland streams.

Not every eroded bank needs repairing. A vertical face beneath a tangle of alder roots, or a small slump on the outside of a bend, is often just the river doing its job. Intervene where erosion is accelerating, where land is being lost at a rate the owner cares about, where sediment is smothering gravels used by spawning trout and lamprey, or where a footpath or bridge is being undermined. The most useful first step is to work out why the bank is failing; otherwise you will be treating the symptom and watching it fail again within a couple of seasons.

Willow spiling: a living retaining wall

Willow spiling is the workhorse of natural bank protection in the UK and it suits brooks and small rivers beautifully. Live willow rods — commonly common osier or purple willow, cut in the dormant season — are woven horizontally between stout stakes driven into the bank at the toe of the slope. The weave is held back by soil backfill and, where the bank is steep, by a coir mat or geotextile behind it.

The clever part is that the willow is alive. As the season warms, the rods root and shoot, producing a dense mat of roots that binds the soil and a thicket of stems that slows the flow at the bank face. Within two or three years you have a self-repairing structure that no longer depends on the stakes. Spacing is usually 1–1.5 m between stakes, with rods 2–3 m long, and the work is best done between late autumn and early spring.

Best on banks up to about 2 m high with a reasonably firm toe
Excellent habitat for invertebrates, nesting birds and fish cover
Needs a local supply of willow and a skilled hand; poor weaving fails quickly

Coir rolls and brushwood bundles

Coir rolls are sausage-shaped rolls of coconut fibre, typically 30–40 cm across, pinned with wooden stakes along the waterline at the toe of a bank. They are not a structural fix on their own, but they do three useful jobs at once: they absorb wave and flow energy, they trap sediment, and they give newly planted wetland vegetation something to root into. Rolls are often supplied pre-planted with sedges, reeds, yellow flag iris or purple loosestrife, which knits the roll into the bank within a season or two.

Brushwood bundles — also called faggots — are the older, cheaper cousin. Bundles of hazel, willow or birch, roughly 30 cm in diameter and a metre or more long, are laid along the toe of the bank, pegged in place with stakes, then backfilled and planted. They are ideal where you want to raise the toe of a slumped bank, build out a narrow berm, or protect a length of bank without heavy machinery. Both techniques work best in combination: a coir roll or faggot at the toe to stop undercutting, spiling or live stakes above it, and native planting behind.

Choosing the right approach for your stretch

Match the technique to the energy of the site rather than to what looks tidiest.

Fast, straight, over-wide reaches: coir rolls or faggots at the toe, plus live stakes, and consider narrowing with berms so the flow picks up the energy it has lost.
Steep, actively eroding outside bends: willow spiling, ideally in short lengths rather than a continuous wall, with large woody material placed at the toe upstream.
Low, poached, boggy margins: brushwood bundles, fencing off livestock and replanting — often the cheapest and most effective answer of all.
Long, gently eroding reaches: nothing structural. Fence, plant native trees and shrubs such as alder, hawthorn and guelder rose, and let roots do the work over a decade.

Timing, consents and aftercare

Almost all of this work is seasonal. Cut and install willow between late autumn and early March, ideally before the end of February so the rods have time to root before the growing season begins. Avoid the bird nesting season from March to August, and avoid periods when salmon and trout are spawning on gravels downstream — on many rivers that means steering clear of late autumn and early winter spates in reaches where redds are likely.

You will usually need permission from the landowner or occupier, and flood defence consent from the Environment Agency in England (or the equivalent regulator in Wales, Scotland and Northern Ireland) before placing any material in or near a main river. Sites designated as Sites of Special Scientific Interest need assent, and where a public footpath runs alongside the water, check that the right of way is not obstructed.

Aftercare is where good schemes earn their reputation. Check stakes and pins after the first two or three spates and re-seat anything that has lifted. Keep livestock out with stock fencing or a temporary electric fence until the vegetation is established. Leave cut willow brash along the channel margins where it can be colonised, and resist the urge to strim or clear the new growth. Give it three growing seasons and the bank will look less like a construction site and more like a river again — which is exactly the point.

Conservation

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5 Comments

Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply
- John Abraham says Jul 21, 2024 at 10:00am
  
  I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
  Reply
  - Robert Sonnysays Jul 21, 2024 at 10:00am
    
    I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
    Reply
Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply

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