Installing coir logs at a bank toe, step by step

A coir log is a dense cylinder of coconut fibre held in a net. Laid along the foot of a bank, it absorbs wave and current energy, traps sediment and gives plants a protected place to root. As the log slowly breaks down, the root mat takes over the job.

Where coir logs work, and where they do not

Coir logs suit streambanks, lake shores, wetlands and coastal banks where water moves slowly. Alaska’s Department of Fish and Game notes they are not recommended for high-velocity areas and work best combined with other revegetation methods rather than as the only toe protection. A watershed non-profit’s stream handbook puts it simply: they stand up to lower-velocity flows, but are not a fix for major erosion.

Typical sizes

Massachusetts’ coastal zone agency describes coir rolls of 12 to 20 inches (about 30 to 50 cm) in diameter, typically 10 to 20 feet (3 to 6 m) long. Smaller diameters suit sheltered sites; larger ones suit exposed sites and steeper banks. More tightly packed logs give more protection at the start; looser ones can be planted more heavily.

Step by step

1. Prepare the bed. Clear rocks and debris. The log must touch the soil along its whole length; never let it bridge gaps between rocks or uneven ground. Work when water levels are low.
2. Bed the log in. Set it at the base of the slope, at about the normal water level, in a trench. Guidance ranges from a shallow trench of about 5 cm to burying two-thirds of the log’s diameter; deeper bedding resists being lifted or undercut.
3. Stake both sides. One installation manual uses 5 × 5 cm (2 × 2 in) wooden stakes, 0.9–1.2 m (3–4 ft) long, two at each end and then alternating sides about every 30 cm (1 ft). Spacing should be adjusted to site conditions.
4. Tie it down. Secure the log with rope or wire tied between stakes, then drive the stakes flush with the top of the log.
5. Join and finish the ends. Lace logs end to end with natural twine. Bury the ends or tie them into the bank: exposed ends are a common cause of failure.
6. Plant. Plant plugs into the log about every 30 cm. Where the log is set above the water, waiting a month or until it is saturated helps the plugs take.

What to expect

Published guidance gives coir logs a life of about three to seven years, depending on how densely they are packed and how exposed the site is. In that time, roots grow through the fibre and into the soil behind it. Inspect after high water and storms, re-tighten ties, replace lost stakes and fill any scour early.

Work below the high-water line often needs a permit. Check local requirements before you start.

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