At Bristol Avon Rivers Trust (BART), we are deeply concerned about the potential impact of proposed development in close proximity to rivers. As our government prioritises growth, we worry that this may come at the cost of nature—particularly our rivers.
Our concerns are twofold:
- during the construction phase, when dirty sediment-laden site run-off often flows directly into the watercourse with little or no treatment
- the longer-term consequences of increased surface water run-off and pollution, coupled with missed opportunities to improve biodiversity through good practice.
The Risks During Construction
From recent site visits across our local river catchments, we have seen first-hand the devastating impact that sediment run-off from development sites can have on local waterways. Without robust mitigation measures in place, that are monitored consistently throughout the entire construction phase, sediment can smother aquatic habitats, degrade water quality, and impact species that rely on clean, oxygen-rich water.
A well-defined sediment and surface water management plan should be a strict condition of planning approval, ensuring that developers take full responsibility for preventing pollution at every stage. It is vital that these plans are adhered to and monitored throughout the entire duration of construction.
In recent cases, in the Bristol Avon catchment, inadequate planning and enforcement led to persistent problems, allowing sediment and pollutants to enter watercourses unchecked. Stronger oversight and accountability are essential to prevent this from happening to our watercourses. This appears to be a grey area, as developers are essentially responsible for assessing their own compliance, given that Planning Authorities lack the resources to monitor sites once permission has been granted.
Beyond Construction: Long-Term Water Management
Once construction is complete, it is crucial to understand how surface water from the new development, including roads, will be managed to reduce flood risk and protect water quality and biodiversity. Many housing developments rely on attenuation ponds for flood mitigation, but there is far greater potential to design solutions that enhance natural habitats while managing water effectively. The four pillars of Sustainable Drainage Systems (SuDS)—water quantity, water quality, biodiversity, and amenity—should be given equal consideration in SuDS design.
Successful examples of this approach can be seen in catchments across the country where well-designed schemes are delivering multiple benefits, including pollution filtration, habitat creation, and improved climate resilience. It would be far more effective to integrate these principles from the outset rather than retrofitting solutions after problems arise.
The Importance of Getting This Right
The Bristol Avon is an ecologically-rich river that supports migratory fish such as brown trout and European eel, along with other species like water voles and otters. These species are highly sensitive to changes in water quality, and increased surface water run-off containing pollutants from roads and urban areas could have long-term consequences for their survival.
While we have not yet seen the detailed development plans linked to local growth plans, we strongly urge planning authorities to ensure that any surface water management strategy is not just sufficient to meet flood risk requirements but also designed to enhance water quality and biodiversity. By taking a more forward-thinking approach, developers and planners have the opportunity to create spaces that support both people and nature.
At BART, we remain committed to advocating for sustainable solutions that protect and restore our precious river environments. We will continue to engage with stakeholders to ensure that developments near our rivers contribute positively rather than adding to the pressures they already face.
