Flooding of Council roads
Council’s local road network system is a large community asset that is essential for connecting our residents and visitors to various essential community services and businesses in our Region.
Flooding can cause extensive damage to roads and property. For the safety of all road users, and to protect the road asset, flood warning and/or road closure signs may be necessary while floodwaters cover roads. Once the floodwater recedes, Council progressively inspects all affected roads and infrastructure to make sure they are safe, can be re-opened to traffic, and take loads of various sizes and weights.
Designing Road Pavements
Road pavements are designed to match the prevailing conditions and available local material. In this area, road design concepts give priority to keeping moisture out of the lower quality paving materials that are available in this area.
Saturated Roads
When a road is inundated, especially for a long time, the materials in the road pavement become saturated. This reduces the strength of the road pavement material.
Council undertakes inspections and testing to re-open roads as soon as possible after inundation. In its custodial role, Council balances protection of the road asset with community and industry access. Roads that have been saturated must be carefully managed to try and reduce the damage caused to them. To do this, road closures, load restrictions and traffic management are the only options available.
Load Restrictions
Once road pavements are saturated, it takes time for moisture to drain from the material and for full-strength properties to return. Restricting the loads on roads during this ‘dry-back’ period is essential to preserve this important community asset.
Based on technical data, reducing the load by 20% reduces the impact on the road pavement materials by about 50%.
Experience shows that a single trip by a fully-loaded transport vehicle may cause permanent failure of the road pavement material, leading to expensive repairs and affecting accessibility to the road network.
Council Engineers will progressively lift load restrictions according to the local conditions. The stages include:
- 5 tonne limit to allow access for local residents and emergency services vehicles;
- 80% of the legal axle loads on transport vehicles as shown in the table;
- removal of load restrictions.
|
Axle Group
|
Legal Road
|
80% Load
|
|
Steer axle
|
Varies
|
No reduction
|
|
Single 4 tyre
|
9.0 t
|
7.2 t
|
|
Tandem 8 tyre
|
16.5 t
|
13.2 t
|
|
Tri 12 tyre
|
20.0 t
|
16.0 t
|
Reference: Transport Operations (Road Use Management - Mass, Dimensions and Loading) Regulation 2005.
Council’s Engineers, in making these decisions, rely on specialist advice based on measurement and analysis of road surface movements under test loading of the pavement. This technique models the ‘dry-back’ process of the road pavement material and allows the decision to be made about when it is safe to remove the load restrictions and open the road fully to all road users.
Traffic management
Managing traffic on saturated road pavements as the roads ‘dry-back’ is important for the safety of road users and for the life of the road asset. Traffic management measures used include:
- using signage to encourage loaded vehicles to travel safely in the middle of the road where possible
- restricting the use of heavy load permits.
Public support
Council understands the impact flooding has on communities and industry, and seeks your assistance in preserving our local road asset following flooding.
Council assures you that we carefully manage road closures and load restrictions to avoid permanent damage of saturated roads and to minimise disruptions to road users.
All road users are urged to follow advice provided on road closures and load restrictions, drive safely to match the conditions, obey road signs and speed limits, and look out for road workers as they go about their job repairing the roads.
In doing so, everyone will play a part in looking after this important community asset.