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What is Drainage Flow Control Device? 7 Important Points

Flow Control

What is drainage flow control?

When there is heavy rain, and underground drainage pipes are full to its capacity, it leads to flooding the downstream pipe network and that leads to flooding the sewer or watercourses. Drainage flow control helps to regulate the rate of flow of surface water from upstream and prevent downstream pipe network from flooding.

Along with its major advantage of flood control, there are many other benefits of flow control such as speed control of upstream surface water, self-cleansing, controlled discharge to the downstream and release of clean water to the environment.

How does flow control work?

To control the upstream surface water, flow control units are used. The unit can work as a standalone unit or work with collective efforts of multiple units (also called flow control system). The control systems are capable of attenuating water, velocity control, release water with controlled flow rates, self-cleansing of water.

Lastly, it can be operated remotely from the control centre which is very useful during heavy rain times and minimise the requirement of site visits.

What are the different types of flow control?

The flow control system works right from the first step which is Attenuation. Please see the flowchart below to quickly understand the various stages of the flow control system.

Drainage Flow chart

What is Surface Water Attenuation?

In recent years, heavy rains, severe storms and flooding are noticed in various cities across the globe. The rapid urbanisation and significant increase of impermeable surfaces (due to physical infrastructure development) lead to generating flooding and damage to the infrastructure as well as livelihoods.

So, what is the solution?

There is no one-line answer to it, but multiple actions could prevent it from happening or minimise it to low severity levels.

Surface water attenuation is one of the key actions to move in this direction.  It simply means collecting surface in a storage tank or crate or pipe and release it slowly with controlled rates.

Following are the key types of Attenuation System:

  1. Attenuation Pond
  2. Large Size Attenuation Pipes
  3. Attenuation Crates
  4. Rainwater Diffusor

Attenuation Pond:

Attenuation Ponds are manmade natural pond to collect the surface water of adjacent highway or motorway or large infrastructure spread in a wide area.

Attenuation Pond is the most practical method to collect and treat surface water runoff. It allows for both sedimentation and biological processes within the pond and as a result, much clearer water is discharged to the downstream network or the outfall.

The positioning and size of the pond are dependent on various parameters such as catchment area of the adjacent road, proximity to outfall such as river or stream, acceptable discharge, ground filtration rate (if acceptable), downstream network capacity, etc.

Large Size Attenuation Pipes:

Large size attenuation pipes deliver the same results as attenuation ponds except for ground filtration. These pipes are made of precast concrete or Plastic materials and come with high strength to withstand heavy vehicular loads.

Attenuation Crates:

Attenuation crates are interlocked crates to store water and release slowly to the ground through infiltration or discharge it the downstream network finally to the outfall points.

Rainwater Diffuser:

Rainwater diffuser collects surface water into the voided sub soil aggregate in permeable or impermeable infiltration system. These diffusers are made of high strength material to withstand heavy vehicular load and very suitable for a car park, residential access or driveways, etc.

blog drainage engineering course

 What is the hydro-brake chamber?

Hydro-brake controls and customises the flow of upstream water. There are no moving parts, and it runs without power supply; as a result, it is a reliable and low maintenance infrastructure to maintain surface water flow.

Hydro-brakes can be customised to suit the site and drainage catchment requirements. Means it can be installed for small to medium to large scale drainage flow control system.

I hope the blog gives you a detailed understanding of flow control devices and associated functioning to control surface water drainage system and minimise the possibility of drainage flooding. Please feel free to like, share and comments.

What is HydoValve?

HydroValve is provided to control the water flow coming from the attenuation tank to a customised rate ranging from 1 litre per second to 50 litres per second. It discharged the water to the downstream network or watercourse.

What is outfall?

The term outfall is applied to the point where the road drainage system discharges into a different type of drainage system:

There are three types of commonly used outfalls:

  • Natural Channels.
  • Watercourses
  • Purpose-made Drainage Channels
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