Slow the Flow

One way we aim to manage flood risk across the catchment is through the installation of l Sustainable Drainage Systems (SuDS) and Natural Flood Management (NFM) measures, such as bioswales and leaky barriers. These approaches work with natural processes to slow the movement of water during heavy rainfall.

Leaky barriers

Leaky barriers (also known as leaky dams) are structures installed within watercourses to slow the flow of water during heavy rainfall, while allowing normal everyday flows to pass through. By temporarily holding back higher flows, they help reduce peak water levels downstream and support more natural sediment movement. As part of this work, leaky barriers are being installed in Norton Common and Pix Meadow in Letchworth Garden City. You can find out more about these projects via the links below.

Leaky barriers factsheet – how they work and what they do

Norton Common and Pix Meadow leaky barriers project briefing note

Bioswales

Bioswales are shallow, planted drainage features designed to manage surface water runoff. They slow and store rainwater at the surface, allowing it to soak away gradually rather than entering drains all at once, reducing pressure on the drainage network during intense rainfall.

Bioswales are being installed at Woolston Avenue / Lawrence Avenue in Letchworth Garden City. Further information is available via the links below.

Bioswales factsheet – how they work and what they do

Woolston Avenue bioswale project briefing note

Constructed wetlands

Constructed wetlands are shallow, engineered basins with specialist soils and wetland planting that slow, store and naturally filter rainwater before releasing it gradually into nearby drains or watercourses.

A constructed wetland is being installed at Howard Gardens in Letchworth Garden City. The wetland will capture surface water flowing towards the Pix Brook during heavy rainfall and release it gradually over time.

Further information is available via the link below:

Howard Gardens constructed wetland project briefing note

Etonbury Woods

Further Natural Flood Management measures are being developed for Etonbury Woods near Arlesey. These are expected to include a combination of measures such as

• leaky barriers: slowing the flow of water through the Pix Brook
• riverbank reshaping: replacing steep edges with more gradual slopes
• tree management: removing diseased or unsuitable trees and replacing with species better suited to wet woodlands.

Further information is available via the link below:

Etonbury Woods Natural Flood Management project briefing note

Monitoring

We’ll monitor the river closely to see how our interventions slow the flow of the water and influence water quality.

A combination of technical experts and our river volunteers will create a monitoring network to look at the flow patterns of the Pix Brook. This network will improve our knowledge around the influence of extreme weather and local flows on the catchment.

All of this information will be shared and used to forecast potential flooding, helping to create a more resilient community.