Table of Contents

5.5 Drainage

Most road drainage assets have a predictable, long physical life, but the service level is often controlled by environmental impacts which affect drainage capacity, particularly scour, sedimentation and debris. As structural risk is generally low, the management focus is to ensure waterway capacity by appropriate operational maintenance, particularly drain and pit clearing and scour repairs. Significant works need to be programmed in response to seasonal patterns, e.g. after heavy storms or bush fires.

Drainage elements beneath the pavement may be subject to deformation or collapse as the result of settlement and/or heavy traffic loadings and failure of the road formation. This can result in significant impacts to the community, especially on busy routes. Accordingly, the management strategy for cross‑drainage elements commonly incorporates programmed inspection of alignment and structural condition, including checking for leakage between sections and signs of invert scour.

The consequences of service failure of pumping stations are significant for public safety, transport efficiency and impact on the physical integrity of pavements. The management strategy commonly adopted seeks a fail-safe service through regular operational maintenance to clear inlets and outlets and pump and power supply maintenance in accordance with design/manufacturers’ specifications.

Table 5.1 presents the management strategy development for drainage and Table 5.2 presents the maintenance practices for drainage.