When upgrading highways, flood estimations typically concentrate on providing a defined maximum probability of flooding (flood immunity) and times of closure at specific crossings (bridges, culverts, floodways). This approach is based on location and assumes hydraulic independence between structures or floodplains.
Highway closure due to flooding is important when planning highway upgrades. The level of service and upgrade priorities become complex when hydraulic interdependency between structures is real.
The Link Flood Study is a framework used to evaluate the interdependency of the linear infrastructure of highway structures. Having applied this on the Bruce Highway and Inland Freight Route, this innovative framework assesses the entire highway and sub-links to determine the interdependency between structures within hydrological / hydraulic models. The flood metrics of Annual Average Time of Closure, Annual Duration of Closure, and number of closures per year are produced for each crossing accounting for interdependence. The economic cost of highway closure, and the upgrade cost is linked to the flood metrics inside the Decision Support Tool (DST). The connection between flooding, economics and costs determines the baseline level of service for the highway.
Within the DST, each structure, sub-link, or link of the highway can be inspected, and upgrade conditions dynamically tested using AATOC, ADC, number of closures, economic benefit and cost. Deciding a level of service for a section (e.g. 1% AEP) produces a prioritised list of structure upgrades required to meet that decision.
The Link Flood Studies have evolved through project development and application. For Inland Freight Route Link Flood Study, “Hydraulically equivalent Hydrology” (HeH) determined “bookended” sequences of long term continuous hydrology to establish efficient hydraulic modelling periods that are undertaken in parallel.
The Decision Support Tool was translated into an open-source platform allowing a greater uptake and use inside TMR, demonstrating the purpose and applicability of the DST for TMR planning purposes.
