By Engineer John Cee Onwualu (FNSE)

The hydraulic design of a drainage channel requires excellent knowledge of the topography and rainfall data of the project area.

The design of a drainage channel is affected by factors such as the topography of the project area, selection type, design frequency, expected volume of stormwater, and economy.

The design discharge is affected by channel section, channel roughness, channel slope, and run-off coefficient factors.

In hydraulic engineering, two types of flow are usually encountered, laminar and turbulent flow. Laminar flow is rarely encountered when dealing with flows in pipes and ducts.

Most flows in nature are turbulent, and this is encountered when dealing with floodwater.

The primary consideration for the final selection of any drainage channel is that its design should be based on appropriate hydrological, hydraulic, and geotechnical analyses, which will lead to economic and efficient hydraulic control systems.

These control systems are the designed Tertiary, Secondary and Primary channels that would safely control and convey stormwater to the natural receivers, without destroying lives and property.

In addition to sound structural design, good construction practices are necessary for a drainage channel to function efficiently.