Mine Flood Protection & Closure

Flood modelling across four separate areas of a base metals operation — pits, waste landforms, a processing area and a camp — sized for two different questions: keeping the site running now, and keeping the final landform intact long after anyone is there to maintain it.

A regional model set the flood behaviour of the main creek system; three local catchment models resolved what happens inside the site, where runoff arrives from the west and the existing bunds were already redirecting it. All of it was built as 2D rain-on-grid in TUFLOW to ARR 2019, with probable maximum precipitation derived separately for the closure case. Terrain came from drone survey where it mattered — one flight over the whole project area, then a second over the processing area alone to pick up a diversion bund that had been built between the two — with regional SRTM at thirty metres filling in the catchment beyond the survey extent. Modelling the bund that exists on the drawing, rather than the one that exists on the ground, is a reliable way to produce a confident answer to the wrong question.

Operations get designed against the 1% AEP because someone is there to respond. A closure landform gets designed against the probable maximum flood, because nobody is — and the test isn't whether it floods but whether flow velocities at the toe stay below the point where the landform starts to unravel.