Quote:
Originally Posted by multiweb
You're pretty switched on Geology Carl. What's your take on QLD geography? Can something been done as a preventive measure? Can it be fixed? More dams? Embakments? Or back to the drawing board? I was asking the same questions the 6th of January in another thread wondering why QLD always get flooded. I was told it's just too flat and almost on sea level?
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It's not a problem that is going to be easily solved. Sometimes a dam is a good measure but in many cases it can make matters worse. You have to be very careful in locating and building the dams because the local geography and underlying geology can all effect how the dam performs in stressed situations, like now. You also have to pick the right kind of dam too. With embankments and such, we need to take a leaf out of nature's book about how they should be constructed. Trying to straighten out the courses of streams and rivers, or channeling floods away from one area only to make matters worse in another, is the wrong way of going about it all. Some of the really big rivers, like the Burdekin, Fitzroy, Clarence, Shoalhaven etc etc, you won't control no matter how much you put into stopping floods. In a good wet season, the Burdekin empties at its mouth twice the volume of water of all the other east coast rivers combined, into the ocean....you can't stop that. You'd need a dam over a mile high just to hold back all the water!!!!.
The problem with QLD is not that it's flat....it's not, except out west of the Divide. It's the amount of rain we get in the time we do. For instance, Mt Bellenden Ker (5000 feet, near Babinda), back in 2002, had 12 metres of rainfall that wet season. But the creeks and rivers like Babinda Ck, Jospehine Ck, Tully River and the streams that run into the Johnstone River, whilst they flooded, managed to handle it. They're fast flowing and are short watercourses that run to the sea within 50 or so miles. It flooded, but nothing to the extent like we're seeing down south. Also, our soils up here can absorb vast amounts of water before they become saturated...those down south can't. It's all to do with their composition and physical makeup. They're not meant to take the rainfall they're getting at present. They saturate quickly and what's left just runs off quickly to the streams and such. You also have different river and stream profiles down south than you get up north. The shape and size of the profiles also dictates how the rivers and streams will act when large amounts of water come down them. Many of the streams and rivers up here can handle much larger volumes of water before the begin to break their banks. They also spread out much wider when they flood.
So, that's what we have to work with and within. Not an easy task, but with a bit of intelligence and integrity, it can be done.