The Impact of Flow Control Devices on Drainage Systems

When a flow control device is added at the end of a drainage run, it regulates the rate at which water is discharged from the system. This is crucial for managing surface water runoff and preventing downstream flooding. However, if not managed properly, this can lead to unintended consequences, such as upstream flooding.

How Flow Control Devices Work

Flow control devices, such as Hydro-Brake® orifice plates, are designed to limit the flow of water to a specified rate. By doing so, they help to prevent the downstream drainage network from becoming overwhelmed during heavy rainfall events. These devices are particularly useful in urban areas where impermeable surfaces, like roads and pavements, increase the volume of runoff.

Hydro-Brake® Vortex Control Devices

Hydro-Brake® vortex control devices, such as the Hydro-Brake® Optimum, are advanced flow control solutions that manage water quantity across a wide range of flows. These devices use vortex technology to regulate flow rates without the need for moving parts or external power sources. 

The Hydro-Brake® Optimum is precision-engineered to meet site-specific flow, head, and storage requirements, providing tailored water management for storm, surface, foul, or combined water.

One of the key benefits of Hydro-Brake® vortex control devices is their ability to deliver effective flood protection and sustainable drainage. They are self-activated and designed to offer reliable, low-maintenance flood management as part of green infrastructure developments. Additionally, the Hydro-Brake® Optimum can be adjusted to accommodate changes in flow rates, ensuring future-proof drainage designs.

Potential for Upstream Flooding

While flow control devices are effective in managing downstream flow rates, they can cause water to back up in the drainage system if not properly accounted for. This backflow can lead to flooding upstream, particularly in areas with limited storage capacity. The water that is held back by the flow control device needs somewhere to go, and if the upstream drainage system cannot accommodate this excess water, it can overflow, leading to localised flooding. This can affect upstream manholes and gullies, causing them to surcharge and overflow. 

Local authorities or water authorities often insist that no flooding occurs within a 1 in 30-year return period, meaning the drainage system must be designed to handle significant storm events without causing upstream flooding.

The Role of Drainage Analysis Software

To mitigate the risk of upstream flooding, it is essential to use sophisticated drainage analysis software, such as Causeway Flow. This software allows drainage engineers to simulate the effects of adding a flow control device to a drainage system. By modelling different scenarios, engineers can predict how the system will behave under various conditions and design sufficient storage to compensate for any backflow.

Causeway Flow provides a comprehensive suite of tools for hydraulic modelling, enabling engineers to create optimal, compliant, and cost-effective drainage designs. It helps in visualising the impact of flow control devices and ensures that the entire drainage network functions efficiently, even during extreme weather events.

Conclusion

In summary, while flow control devices are essential for managing surface water runoff and preventing downstream flooding, they can cause upstream flooding if not managed properly.

Using advanced drainage analysis software like Causeway Flow allows engineers to simulate and design effective drainage systems that account for the potential backflow, ensuring that both upstream and downstream areas are protected from flooding.

By leveraging these tools, we can create sustainable and resilient drainage systems that safeguard communities and infrastructure from the adverse effects of heavy rainfall and flooding.