When the Todd floods, the water carries a quantity of …

Comment on LETTER: Removing sand from the Todd makes no sense as a flood mitigation measure by Hal Duell.

When the Todd floods, the water carries a quantity of sand. Is that fair?
Then, if the flow is slowed, some of the carried sand drops. Is that fair?
The causeways, but especially the Taffy Pick crossing, slow all floods. Is that fair?
Economic constraints dictate that we will never get rid of, or even rebuild, all the causeways. But we could lose the Taffy Pick crossing, not by replacing it with a bridge (economic constraints again, and possibly geographic ones as well), but by replacing it with a level crossing.
If we did that, in the next flood wouldn’t at least some of the recently deposited sand from either side of the crossing flow out through the Gap?
I question if this work would mean a rate hike. I thought the crossing was the responsibility of the NT government who, I have been told, insisted that the original builders of the casino put that crossing across the Todd. If this is true, who owns it now?
Surely the removal of up to one meter of sand from the junction of the Bradshaw and Bloomfield drainage systems with the Todd River increased the flow of flood water through the Gap. I don’t know if that counts as sand-mining or not, and I don’t see it making, or even hinting at, a “concrete drain”.
I too am all for “best practice” in the Todd, but what is best practice? If anyone thinks we can find one clear scientific opinion on this, I suggest they try to follow the global warming debate in which scientists of all stripes seemingly cannot find any common points of agreement.
This may change after Cyclone Sandy, but I doubt it.
While we look for that elusive best practice, and await funding and process for a flood-mitigation dam, how about we petition the NT government to level the Taffy Pick crossing. It would be a start.

Hal Duell Also Commented

LETTER: Removing sand from the Todd makes no sense as a flood mitigation measure
@Alex
Thanks for the explanation.
I will admit that I still think it was better to remove the built-up sand, couch and all, rather than wait for a flood to do it. Chinaman’s Creek drains most of Alice Springs west of the Stuart Highway, more or less, and I like the idea of any water coming down that system exiting thru The Gap as quickly as possible.
(Where does the run-off from the old Racecourse area go?)
I agree with your comments about a river’s ability to alter its own banks. I too have seen that happen, although a bit further downstream. I have been told this phenomenon is known as a “hungry river”, and not much can stop it once it gets its teeth in.
Perhaps that is another reason to remove any built-up sand before a flood – let any flood go through without getting its teeth in.
To minimise the chance of that happening between the Telegraph Station and The Gap, I hope the sand currently being removed be ASTC is only being taken from the middle channels, and not from the sides.
One more comment about the Taffy Pick crossing – in answer to a question at last night’s committee meetings, I learned that the crossing belongs to the NTG. This means that if it is to be knocked down to a level crossing, they are the ones to do it.


LETTER: Removing sand from the Todd makes no sense as a flood mitigation measure
@Charlie
Are you saying that it was either wrong or unnecessary to remove the built-up sand earlier this year from the junction of the Bradshaw and Bloomfield drainage systems and the Todd River. (Is that Chinaman’s Creek? I heard that somewhere, but now can’t find it anywhere.)
The Todd’s bed was about one meter higher than the bed of the drainage system, and was heavily anchored with couch grass too thick to walk through.
I don’t know if grasses like couch and buffel are why sand builds up, but I suspect they help hold it when it does.
Also, do you think that when flood water is checked, it drops some of its load? And if it does, does that impact on the flow of subsequent floods? This question leads into the Taffy Pick crossing, so don’t answer it if you don’t want to.


LETTER: Removing sand from the Todd makes no sense as a flood mitigation measure
Since my last post, I have been informed that the Taffy Pick Causeway was built with money from the NTG, the Commonwealth and a contribution from Hotels Australia, or whoever the home page of the first casino operators belonged to.
The responsibility for its maintenance was accepted by (dumped on?) a reluctant Alice Springs Town Council in the late 1980s.
But who owns it today? Before it can be replaced with a level crossing, or even a bridge if that kind of money is available, that question needs answering.


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