Culverts play a major role in Australian roads and transport, and can be described as the hidden hero of the infrastructure sector. They are responsible for managing underground sewage and rainwater, allowing water, flora and fauna to flow freely under road and rail corridors. With such a vital contribution to our communities, road infrastructure and travel capability, it is important for authorities to adequately maintain these assets correctly.

Culvert design is based on factors like the weight of the surrounding soil and roads, foundation soil types and the expected water properties and their flow rates.

They need to be constructed with a suitable ‘hydraulic capacity’, capable of handling flood water with annual exceedance probability (AEP) up to two per cent, or an average recurrence interval (ARI) up to 50 or 100 years.

Culverts’ hydraulic capacities are typically designed to protect against ‘1 in 100 year’ events, which are significant flood events that have a one per cent chance of occurring in any given year.

Unfortunately, substantial flood events often occur more frequently, making hydraulic capacities inadequate and putting undue stress on undersized culverts. As a result, many culverts are prone to damage, which has considerable ramifications for roads and rail corridors.

The conventional approach to repairing, reinforcing and relining culverts is to add a layer of new cement-based material over any damage to minimise deterioration.

However, added layers of cement-based materials decrease the culvert’s cavity, which reduces flow rate and overall water capacity.

Culverts with lower hydraulic capacity are less effective during flood events, leading councils to face the costly task of replacing the existing infrastructure. Such works can be lengthy and impact traffic flow, the local environment and ultimately the surrounding community.

It is why ground engineering experts like Mainmark recommend more proactive culvert damage mitigation. Culverts should not be forgotten underneath our roads and rail infrastructure; they should be inspected regularly to ensure all blockages are removed and checked for corrosion, settlement, joint or compression failures, water ingress and fire damage.

Any potential hazards affecting a culvert’s structural integrity should be acted upon immediately. Traditional cement-based materials and culvert re-sleeving still hold merit as repair solutions, but there are now additional solutions available that are more effective than these conventional methods.

Mainmark’s vinyl ester structural coatings, for example, are a relining solution that can replace the strength of the concrete without the added thickness of conventional materials. With only a thin 12 to 15 millimetres of application required, this type of lining minimises the loss of hydraulic capacity.

By utilising these modern solutions, culverts can continue performing their vital role of managing water flow and keeping communities safe, without the considerable cost of replacement. With a faster and less disruptive approach, downtime is reduced and higher performance flow rates can be achieved, extending the lifespan of the culvert.

This a sponsored editorial brought to you by Mainmark, for more information head to

About Mainmark

Mainmark provides a range of specialist ground engineering and asset preservation solutions for residential, commercial, industrial, civil infrastructure and mining sectors.

Committed to excellence, Mainmark’s state-of-the-art solutions are backed by more than 25 years of engineering expertise. Mainmark has 15 sites across Australia, New Zealand, Japan and the UK.

Mainmark products and services include solutions for ground stabilisation, void filling, stopping water ingress, raising and levelling on-ground and in-ground structures, fixing anchors into rock faces and embankments, and other related ground engineering processes.


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