All that water has to go somewhere, and one of the avenues that delivers it to its destination (apart from the O’Connell and Proserpine Rivers) is the system of wetlands that come with the meanderings of Lethe Brook, particularly the part you encounter just north of the Whitsunday Coast Airport.
Now, you could, should you feel inclined to spend all that money to raise the highway beyond the point where it’s going to go under in an average wet season, but you’d be needing to put enough drainage in place to ensure you don’t create a massive artificial lake every year, and when you get a cyclone, a once in a decade or once in a century weather event even that level won’t be high enough.
From there, you’ve got a number of other trouble spots that could be fixed (Sandy Gully, just north of Merinda is one, though I suspect the problem there has a lot to do with the railway embankment on the line that delivers coal to Abbot Point, north of Bowen) but you strike the next big hurdle, and the next substantial flood plain as you skirt the hill at Inkerman and strike the Burdekin delta.
You’ve passed other areas that can be a problem in The Wet, but let’s confine our attention to the stretch that takes you through Home Hill, Ayr and Brandon, across the once notorious Barattas, past Giru and the Houghton to the foothills of the Mount Elliot range at Mount Surround.
That’s four urban centres in the space of sixty kilometres, one of which (Giru) seems to suffer multiple inundations every wet season. Flood proofing the highway that runs through those centres is going to cost squillions, and there will, inevitably, be issues associated with drainage when you have the runoff from just under 130,000 square kilometres, the fourth-largest river in Australia in terms of the quantity of water flowing down the channel, running, once again, at right angles to the roadway.
Then, having passed through another patch of dry tropics on either side of Townsville, hit the wet bit around Rollingstone and passed through Ingham and crossed the Cardwell Range you hit the really wet part of the coastline on the run into Tully, with the lowlands around the Murray Flats and Euramo as another stretch of roadway you can bet is going to go under just about every year.