Stabilize riverbanks

Overall effectiveness category Evidence not assessed
Number of studies: 1
Share Tweet Email

View assessment score

How is the evidence assessed?

Effectiveness

not assessed
Certainty

not assessed
Harms

not assessed

Calculating overall effectiveness category

Background information and definitions

Riverbank stabilization is a restoration technique aimed at reducing erosion and sedimentation in river systems, which can degrade anguillid eel habitats. This process involves reinforcing or restoring the natural structure of riverbanks to prevent them from collapsing or eroding. This may be done using natural materials like coir (coconut fibre) or logs, or by installing harder structures such as rock armouring (or rock ‘rip rap’) (Tisserant et al. 2021).

Planting vegetation may also create stability as root systems can help to bind the soil together (see ‘Plant bankside vegetation’). Preventing livestock trampling may help to reduce erosion, see ‘Threat: Aquaculture and agriculture – Exclude livestock from riverbanks’.

^{Tisserant M., Bourgeois B., González E., Evette A. & Poulin M. (2021) Controlling erosion while fostering plant biodiversity: a comparison of riverbank stabilization techniques. Ecological Engineering, 127, 106387. https://doi.org/10.1016/j.ecoleng.2021.106387}

Study locations

Key messages

 One study evaluated the effects of stabilizing riverbanks on anguillid eel populations in inland habitats. The study was in New Zealand.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One controlled, before-and-after study in New Zealand found that after stabilizing riverbanks, longfin eel biomass decreased one year later (by almost half) but reached similar levels to before stabilization after 2–3 years.

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A controlled, before-and-after study in 2014–2017 in a river in Southland, New Zealand (Holmes et al. 2019) found that after stabilizing riverbanks by creating a shallower slope, longfin eel Anguilla dieffenbachii biomass decreased after the first year but reached similar levels to before stabilization after 2–3 years. Average eel biomass decreased by 49% one year after stabilizing the riverbanks (5 g/m²) compared to two months before (9 g/m²). Average eel biomass did not differ significantly two (6 g/m²) and three years (11 g/m²) after riverbank stabilization compared to two months before. Meanwhile, over the same period in unmodified streams, eel biomass increased by 160% from two months before (12 g/m²) to one year after (32 g/m²) but did not differ significantly after two (11 g/m²) and three years (9 g/m²). In March 2014, three 40-m river sections that had previously been straightened were stabilized by reducing the angle of both banks to a 1:2 slope. Three 40-m unmodified river sections 4 km upstream were used as a comparison. A total of 432 eels were caught by electrofishing within stop-nets (6-mm mesh) over four 5-day periods: two months before and for three years after (2015–2017) stabilizing.
Study and other actions tested
Referenced paper
Holmes R.J., Hayes J.W., Closs G.P., Beech M., Jary M. & Matthaei C.D. (2019) Mechanically reshaping stream banks alters fish community composition. River Research and Applications, 35, 247-258.

Please cite as:

Cutts V., Berthinussen A., Reynolds S.A., Clarhäll A., Land M., Smith R.K. & Sutherland W.J. (2024) Eel Conservation in Inland Habitats: Global evidence for the effects of actions to conserve anguillid eels. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Eel Conservation in Inland Habitats

Related Actions

Actions	Effectiveness	Studies	Category
Stabilize riverbanks Action Link	Evidence not assessed	1	Synopsis Link
Create or restore pool and riffle sequences Action Link	No evidence found (no assessment)	0	Synopsis Link
Add nitrogen and phosphorus to nutrient-limited rivers Action Link	No evidence found (no assessment)	0	Synopsis Link