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8 important Facts About Stormwater Drainage Systems

By Engr. John Cee Onwualu

“Stormwater drainage systems are essential to our health and safety – they help protect us from flooding and prevent water pollution, making them an important part of our infrastructure.” Engr. John Cee Onwualu

What is a Stormwater Drainage System?

A stormwater drainage system is an infrastructure constructed to receive and evacuate precipitation from rainfall runoff on the road surface and from the surrounding environment.

A stormwater drainage system can be made of concrete or steel structures and come in different shapes and sizes. It could serve as a surface drainage system or conduit (sewer) drainage system.

Why are Stormwater Drainage Systems Needed?

A stormwater drainage system is needed to evacuate excess floodwater from the environment that could not be absorbed by the soil due to the soil pores attaining a supersaturated state, thereby preventing damage to life and properties by conveying this excess floodwater to the streams or rivers.

How does a Stormwater Drainage System Work?

A stormwater drainage system is an infrastructure constructed as a receiver of precipitated rainfall runoff from the surface of the road or environment, which it efficiently and safely conveys to a bigger waterbody or river.

How do you fix or clean a Stormwater Drainage?

For the fact that stormwater drainage conveys flood water, it contains suspended debris or loose soil particles as it flows along its path which it drops as silt deposit as the flow velocity reduces.

These deposits are manually or mechanically excavated periodically. A stormwater drainage system can be constructed as a precast member or cast-in-place concrete member.

What is the difference between a Drainage System and a Drainage Pattern?

A drainage system is defined as a channel that conveys surface water from precipitation into a waterbody or wetland while a drainage pattern is a pattern created on the surface of the earth by erosion, stream, or river flow over a particular area.

Drainage patterns are more noticeable in areas with steep gradients and poor topography.

How do you drain a Stormwater Runoff?

A stormwater runoff is a result of precipitation from excessive rainfall, which the soil is not able to absorb by infiltration. It is drained by the construction of earth drain channels, concrete drain channels or steel sheet channels.

How do you design a Stormwater Drainage System?

Stormwater drainage systems can be designed through the following procedures:

  1. Having a good knowledge of the topography of the area
  2. Identification of the drainage basin
  3. Collection of surface ground data for rainfall modelling
  4. Knowledge of imperviousness and soil types
  5. Identification and location of underground services
  6. Creation of drainage boundaries or catchments
  7. Computation of peak discharges from each Sub-catchment or catchment areas using the Rational formula: Q = CiA
  8. Design and selection of channel sections, using the continuity equion of Manning-Che’zy equation: Qp = (AR2/3S1/2)/n

Read Also: Considerations in the design of stormwater channels

What is a Barrage?

A barrage, by definition, is a wire structure fitted with gates to regulate the water level in the river in order to divert the water to a canal situated at the bank of the river for the purpose of irrigation, domestic use, power generation, and flow augmentation to another river.

Read Also: 7 Ways To Handle Flooding in Any Part of Nigeria