Draining Large Flat Pavements

All designers know that draining large flat pavements can be a challenge, but a good design, along with a hydraulically efficient drainage system, can eliminate hazards and provide a long-lasting, durable solution that performs as intended.

Poorly designed drainage systems are not only ineffective at clearing surface water quickly, but can be difficult to maintain and cause slip hazards from ponding. These hazards can be avoided with the correct approach and the right products.

With years of experience and numerous research and development competency centres globally and locally, ACO understands the importance that slope plays on drainage performance.

Achieve optimum hydraulic efficiency

There is a wide range of surface drainage systems for various applications, but when it comes to discharging surface water efficiently, it depends on how the trench drain is configured.

Trench drains are designed to intercept and direct surface runoff from a pavement through grates and into channels and finally to an underground pipe system or culvert. One key factor influencing the hydraulic performance of surface drainage systems is gravity. Therefore, the effect of the ground slope and a channels built-in fall is critical.

How does the slope affect hydraulic performance?

As the degree of slope (fall) along the channel invert increases, the velocity of the flow within the trench drain will also increase resulting in a more hydraulically efficient trench drain. The slope can be introduced into the design of the trench drain by one or a combination of the following:

• For flat pavements, introduce a stepped configuration using neutral channels with varying depths creating a stepped fall configuration or introduce a slope along the base of the trench run using sloped channels with built-in falls
• Existing pavement with natural ground fall using neutral channels with a constant depth resulting in an invert slope identical to the ground fall
• Existing pavement with natural ground fall in combination with slope along the base of the trench run using sloped channels with built-in falls to further increase the invert depth

Introducing a stepped configuration has the least positive impact on a trench drain’s hydraulic performance. On flat level pavements, particularly with long runs, velocities are limited by significant lengths of neutral channels with no slope (fall).

In comparison, drainage runs comprising continuous sloped channels with built-in falls allow for positive drainage with greater flow velocities for optimum hydraulic performance.

Drainage flat pavement options

Draining flat pavements in the urban environment is challenging. The 0.5% internal slope in ACO’s modular channels help to compliment the design of flat and level pavements for pedestrian safety. ACO’s Polycrete^® Channels provide a continuous sloped run in flat pavements to achive:

• 40 metres in one direction (end outlet)
• 80 metres in two directions (central or end outlets)

Click here to find out how ACO can help you with your next project.