Improving the River Blackwater

The South East Rivers Trust has delivered nature based restoration works along a stretch of the Blackwater River near the Ivy Recreation Ground in Aldershot, Hampshire.

Like many other urban rivers the Blackwater – a tributary of the River Loddon – has been historically modified, resulting in a channel with very little habitat diversity and wildlife, with no ability for the river to restore itself.

The first phase of the project began in 2021, with the first work in February 2022. Other phases took place during successive Loddon Rivers Weeks, with the help of volunteers.

A riverbed deep in silt

With funding from the Environment Agency, and the collaboration of the Blackwater Valley Countryside Partnership, the South East Rivers Trust is carrying out work that will improve the river habitat and its wildlife.

In the past, the Blackwater’s profile has been artificially changed, which has resulted in a slow flowing river that is deep in silt.

Dense tree growth also restricts light to the river, preventing vibrant aquatic plant life from establishing. The result of this is a river with poor habitat for wildlife that was in need of a helping hand to recover.

Ivy Road Rec before work began

Narrowing the channel with berms

With material arising from tree works aiming to increase light in the river, we installed low level brash berms.

These berms narrow the channel, increasing flow speeds which cleans the river gravels and creates excellent spawning habitat for fish.

Over time, the berms will collect sediment, which in turn will become vegetated and in time will develop to become part of the bank.

A brash berm after construction at Ivy Road Rec

Increasing light

To let light in, we thinned the tree cover along the banks, encouraging instream plants to grow and provide habitat for invertebrates and fish.

The Blackwater Valley Countryside Partnership helped us to determine which trees could be felled without disrupting wildlife, notably bats.

Removing bank vegetation to increase light at Ivy Road Rec

Adding woody materials

In a natural system, trees would fall into the river, disrupt the flow and create a wider diversity of habitats such as deep pools as well as providing shelter for young fish.

To replicate this, we introduced several pieces of large woody material into the river channel. Due to the potential of flood risk in the area, we made sure that they are safely in place and look as natural as possible.

Fixing large woody material in place at Ivy Road Recreation Ground

Hinging blackthorn scrub

Through the winter months of 2023-24, our river restoration team returned to the Blackwater Stream in Aldershot.

The task this time involved ‘hinging’ the dense blackthorn scrub growing on the bank. The technique – which involves cutting half-way through the trunk – allowed the Blackthorn to bend and fall into the river.

Introducing woody material into the channel in this way creates habitat and diverse flow conditions, while not blocking the channel.

By remaining connected to their roots, the blackthorn plants will continue to grow and provide a valuable source of food and cover for birds.

Blackthorn scrub has been bent into the river

Thanks to our supporters

Environment Agency