By Anton Lang ~
Recently in North Queensland, Cyclone Debbie, a high Category 4 cyclone, came ashore in the Area near Bowen and Proserpine. That area is around 400 Kilometres (250 Miles) North of Rockhampton. That was almost two weeks ago now. The damage caused by Cyclone Debbie was horrendous. As the Cyclone moved slowly inland, more slowly than most Cyclones, the intensity decreased until it was classified as a Tropical Rain Depression.
The size of the Cyclone was quite large, and even as the intensity decreased, it was still a large System. What was now a large rain event then turned and moved South. It passed around 250 Kilometres to the West of Rockhampton, continuing on its Southerly direction. It then moved into South East Queensland and also into the area of Northern New South Wales. This is is very intensely populated with many millions of people.
This now major rain event caused probably the worst flooding ever experienced across that very large area, and in some places, it was the worst flooding on record.
River heights rose and consumed large areas of homes, and it all happened with a speed never before seen.
Now, almost a week later, that flooding has receded in the main, and the clean up is well under way.
However, back here in Rockhampton, the Fitzroy River is still rising here in the city. Over the last few days I have received a number of telephone calls, mainly from family members, and also from some friends. They all ask how we are faring, and will the flood directly impact us where we live here on the North side of the River, and the City centre. My reply is that we are safe here, and no matter how high the River does rise, we will still be safe from the rising waters perhaps flooding our home. Most of those callers ask how I can be so certain.
At the time of the last major flood in 2011, I made a number of Posts at this site, and as part of making those Posts, I did a lot of research. Part of that research was to look at the flood maps which showed the extent of the flood and just where it would reach at its extent. Those flood maps have been updated since that 2011 flood, and the most recent flood impact map shows where the floodwaters would extend to if the River level was to reach 9.5 Metres, which is 400mm higher than that 2011 flood, and that 400mm translates to 16 inches. Even if the River was to rise to that level, the floodwaters would still be at least half a kilometre from where we live. So that is how I knew we would be safe.
The River level was originally mapped to reach a level of 9.4 Metres, which is 300mm (12 Inches) higher than that 2011 level. If it was to reach that height, this would be the worst flood event here since the 1954 flood.
That River height has been revised down now to perhaps reach only 9 Metres, and while originally expected on Wednesday afternoon some time, it is now not expected to be until some time on the Thursday morning.
All of this led to a further question from nearly all of those family callers.
They wondered why that when the Cyclone was two weeks ago, and then, after it moved into that South East corner of the State, where the floods have in the main cleared up, then why was it that Rockhampton has still not reached its peak.
Again, all of that also goes back to the research I did during that 2011 flood.
It has everything to do with the immense size of the Fitzroy River Basin, the second largest River Basin in Australia, after the huge Murray Darling Basin. The image shows this vast River Basin, and if you click on the image, it will open in a new and larger window so you can see it a little better.
From the small map of the State of Queensland you can see this river basin covers a very large area of the State.
Rockhampton is at the right of the yellow section on the larger map at about half way down the map.
The river flowing from the South is the Dawson. The Don and its tributaries flow into that river.
The river from the north is the McKenzie, which flows from where you see ‘Emerald’ on that map.
Into the McKenzie flow the Nogoa, and the Comet, which changes name at Rolleston. Theresa Creek also flows into the Nogoa below Fairbairn Dam, (Lake Maraboon)
From further north flows the Isaac and into that flows the Connors. The Isaac flows into the McKenzie.
The McKenzie and the Dawson join to become the Fitzroy at around mid screen near the town of Dauringa there, and the Fitzroy then makes its way all around the map as it moves through Rockhampton and into the Pacific Ocean.
Every single one of these rivers and creeks are in major flood, and this is only the second time this has happened, the first during that 2011 flood.
As you can also see, there are many dams and weirs on all these rivers and creeks, but nothing whatsoever could have held back a flood of this mammoth proportion.
Also keep in mind that the flood waters are flowing at around 10 MPH, so that is why that flood water flow takes so long to travel down what is effectively hundreds of miles of rivers in this area.
That is why that flood level will stay above the major level (8.5 Metres) here in Rockhampton for a long time to come.
Below are the most recent River heights in this immense River Basin, and here, the number after the name of the recording Station is indicated in Metres.
Latest River Heights:
Isaac R at Yatton TM, 12.22, Falling, 10:00 AM TUE 04/04/17
Mackenzie R at Tartrus TM, 13.90, Falling, 02:15 PM MON 03/04/17
Dawson R at Knebworth TM, 11.308, Falling, 10:00 AM TUE 04/04/17
Fitzroy R at Riverslea-2 TM, 25.93, Steady, 10:30 AM TUE 04/04/17
Fitzroy R at Yaamba, 15.20, Rising, 09:00 AM TUE 04/04/17
Fitzroy R at Rockhampton, 7.75, Rising, 11:00 AM TUE 04/04/17
So, while flooding has receded in most areas affected by what was originally Cyclone Debbie, the flooding here in Rockhampton has a long time to go before it begins to also recede, considering that it hasn’t even reached its peak yet.
Anton Lang uses the screen name of TonyfromOz, and he writes at this site, PA Pundits International on topics related to electrical power generation, from all sources, concentrating mainly on Renewable Power, and how the two most favoured methods of renewable power generation, Wind Power and all versions of Solar Power, fail comprehensively to deliver levels of power required to replace traditional power generation. His Bio is at this link.