Intertidal Planting Solution on River Thames

Salix were approached for design support on an intertidal project on the Thames, just shy of the Thames Tidal Barrier.

The Salix Bioengineering solution of Rock Rolls /Pre-established Coir Rolls was adopted as the design.

This solution was able to address the technical concerns of the Environment Agency and has created an effective reedbed habitat. Two years after the installation the reed bed
is flourishing.

The brief was

• The plants must cope with brackish water
• A level bed with alternating dry periods or sudden inundation
• Allow for a rush of water, and often wave energy that reflects back off the vertical walls, creating a zone of extra turbulence
• When emptying, the plants, the sediment accreted and the base growing medium must all be retained within the terrace
• Provide a long-term reed bed solution as a potential habitat

A novel solution to a terrace intertidal habitat

In August 2015 Common Reed, pre-established in Coir Rolls were installed alongside the Rock Roll component.

The Common Reed, Phragmites australis is tolerant of brackish water and frequent inundation. The reeds were established in a Coir Roll off site at our wetland nursery in Norfolk.

The reed plants will go on to establish further roots into the base material and also colonise the interstices of the adjacent Rock Rolls. By colonising the Rock Rolls the reed population now has an overall long-term stability against pulses of high energy turbulence created by the influx and retreat of the tidal waters.

The combination of permanent Rock Rolls and biodegradable Coir Rolls will provide a range of sediment traps that will benefit the biodiversity of the habitat in the future.

And the result two years on is one to be proud of, the reeds have filled the terrace and the habitat is firmly established for the benefit of a wide range of wildlife.