The importance of wiggles in a river system

Volunteers installing large woody deflectors in the River Roding to improve flow and habitat diversity.

Rivers should be biodiversity and wildlife havens, teeming with curves and meanders that provide a variety of habitats for their residents. However, sadly, the most common sights today are straightened, corralled waterways. 97% of UK rivers have been modified in some way, leaving only 3% classified as free flowing.

For many decades, rivers have been straightened to increase the availability of usable land for agriculture and development, as well as to facilitate shipping as water flows more easily and quickly in a straight line. There was also the idea that straightening waterways and dredging channels would decrease flood risks in the local area by disconnecting rivers from their floodplains. However, this simply moves the flooding issue downstream.

These changes have negatively impacted the health of our waterways and entire ecosystems. Fast-moving water can lead a river to gouge deeper and further divert it from its floodplain. It also affects downstream sections by carrying more sediment in this direction. The worst impacts, however, come from a biodiversity point of view. Uniform flow rates decrease habitat diversity in the river system, driving species elsewhere. Faster-flowing water deprives fish species of spawning grounds and shelter areas, also affecting all the other organisms that either live or depend on freshwater ecosystems such as vertebrates and birds. The removal of natural vegetation on the riverbanks influences water temperature by reducing shade from trees and nutrient availability as it reduces the amount of organic matter, such as leaves, stems and branches in the soil.

As environmentalists became aware of the negative impacts of channelisation on river health and ecology, efforts to return waterways to their natural state have begun and are known as remeandering or rewiggling. This is a river restoration process that adds bends and curves to waterways, aiming to return them to a more natural state and when possible, reconnect them to their floodplains.

Rewiggling benefits both people and biodiversity. Reconnecting a river to its floodplain and adding meanders increase storage capacity in the river system and reduce water speed, and, therefore, flood risks. From an environmental perspective, it allows space for nature to recover and creates thriving ecosystems across the floodplain such as wetlands, which are biodiversity hotspots and have a great carbon storage capacity. It also provides complex and diverse habitats where wildlife can thrive. A natural river has a mix of slow-flowing, static and turbulent areas, which allows vegetation to get established and provides shelter and spawning grounds for wildlife, besides other various advantages.

At Thames21, we aim to reinstate natural processes in our river restoration projects both by rewiggling, like in the Action for Silk Stream project at Chandos Park, and the Glassmill Pond, and also by adding wood deflectors and brash berms, which are another way to boost flow and habitat diversity. Some examples are the River Roding restoration project, Community Action for The Cut and the Quaggy Habitats – Capel Manor Project, to name a few.

Join us in our mission to protect and restore London’s rivers by volunteering, donating, or fundraising for us.