It's official - Bonnet Carre Spillway to open tomorrow AM

first virus....

next raging waters....

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Link?

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Lazy Bastard

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Sad. But they should open both

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Geez

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Sad. But they should open both.

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Negative

Chinese Carp season gets back into full swing next week!

Get those mirrolures ready.

Goodbye cheap crawfish.

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The strongly resisted last year. Last time it was open several issues with half the gates and now inoperable. Its a last resort measure because there is a fear they may never get it to close again.

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Opening the BCS is horrible.

Opening Morganza is cataclysmic because as you said, it might well fail while opened.

Would be nice if we could actually get it fixed / replaced so it would be a viable option.

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Sad. But they should open both.

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I see this thought a lot and want to provide a basic hydraulics and sediment transport lesson to all. I wanted to dumb this down, but surely some armchair engineers will jump in and argue, so to you guys:

1) Look up Lane's Balance. It is a conceptual model that relates river behavior and response to changes.

2) Rivers move sediment, not just water.
3) Lighter sediments (e.g. silts and other fine-grained particulate) comprise about 80% of the MR's total sediment load. Heavier sediments (e.g. sand) comprise the remaining 20%. The sand literally sits on the bottom of the river in dunes for all flows below ~400,000 cfs; but as the river gains flow/energy, the sand begins to roll down the bed. By 1.2 million cfs, which is the Bonnet Carre trigger, the sand is nearly fully suspended within the water column and no longer just flowing along the bottom.
3) Opening Morganza, which is upstream of the Bonnet Carre, reduces the energy of the river, causing heavier sediments to fall out of suspension (referring to main channel, not the diversion channel). Induced shoaling via energy/flow removal is a widely studied and well understood phenomenon. It happens down stream of ORCS, it happens downstream of Bonnet Carre when open. Further reading.
4) Remember Lane's Balance? We are not removing an equal relationship of sediment and water, as rivers have a non-homogenous mix of water and material at various points. Thus, the balance will tip such that we are in a bed aggregation phase, which is not good for shipping and not good as the river's carrying capacity could drive flood elevations higher on the levees due to bed elevation.
5) In closing, one reason of many that Morganza is opened later is to maintain enough stream power to prevent further shoaling. Plenty of higher level reading available One old example.

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Wouldn't it 'close' when the water goes down?

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By close that means back to the 70/30 split.

The MS river wants to follow the Morganza channel / Atchafalaya channel. The concern is that even as the water naturally drops, it won't return back to that 70/30 ratio.