re: Louisiana not waiting for barrier approval any longer

i have a feeling this argument is biology vs. engineering. i can agree that sediment diversions are highly necessary, we need them; but if you just build diversions and let the islands go to shite, you are only capturing the sand and coarse fines which are heavy enough to settle out in the tail-water basin. coarse fines constitute only 20% of the total sediments that travel through the river. the other 80% are silty fines that will not settle out rapidly; it takes them a lot longer. i wasnt asserting we somehow would end littoral drift, but you do help erosion rates greatly in the medium-term. raccoon island is a perfect example. it actually got bigger when they restored it due to sand shoals just to its east, which were the sediment source. if we restore most of the barrier islands, they all benefit from the one next to them, whereas if you restore one at a time (like we've been doing to the past 15 years), none of the others really benefit, and you are back rebuilding it a decade later.

how does OCPR build marsh creation projects? they build a retention berm, then pump dredged slurry into it and let it all settle. think of the islands as your berm. without them, the fines will just float out into the gulf and are gone. so now we have a 100 million dollar sediment diversion that is 20% efficient. great. if you ever want to recreate marsh effectively, you need some mechanism to capture the sediment. do you think the state legislature or congress will fund a 100+ million dollar diversion that is less than even 50% efficient? why has west bay failed as a sediment diversion? there is nothing to capture the fines on the back side, they just float away. now the corps wants to plug it.

DNR and the corps have been studying the proposed myrtle grove diversion for years now, and will be studying it for another 10+ years. this is the largest proposed diversion and the upper flowrate limit that is being thrown around is maybe 50,000 cfs. right now the river is flowing around 800,000 cfs. considering peak flow of the river is 1.2 million cfs; 50k is a drop in the bucket. davis pond and caenarvon, the two biggest existing diversions, are only 8-10,000 cfs. and it took decades to get them built.

we arent going to wake up tomorrow or in ten years and be able to just start building the size of sediment diversions we need due to red tape bullshite. to get land building results on par with wax lake or atchafalaya delta, you would need at least a 100,000 cfs diversion structure. none are planned, or even on the drawing board.

politics and money is what it all comes down to. when there is a decent chance to accomplish one of the steps on the list of things needed to rebuild and protect our coast, we have to jump on it regardless of whether its the right order or not. its a new mindset that must be adopted to get things done around here because we have been theorizing for 40 years about the best way...what does it lead to? more studies and theories.

also, if we are talking land-building diversions, then it's a given that wildlife habitats will be destroyed before they are rebuilt. oyster beds will be silted over etc. etc. one way or the other, the habitat will be completely re arranged and it will affect animal numbers and behaviors.

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the other 80% are silty fines that will not settle out rapidly; it takes them a lot longer.

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Not when you take into account the properties of silts and clays to combine rapidly...plus the way they align themselves in marshes actually makes them less susceptible to longshore drift and Ekman Transport.

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how does OCPR build marsh creation projects? they build a retention berm, then pump dredged slurry into it. think of the islands as your berm. without them, the fines will just float out into the gulf and are gone. so now we have a 100 million dollar sediment diversion that is 20% efficient. great. if you ever want to recreate marsh effectively, you need some mechanism to capture the sediment. do you think the state legislature or congress will fund a 100+ million dollar diversion that is less than even 50% efficient?

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You're not creating a marsh, BTW how many of those "created" marshes function as well or as lonmg as natural marshes. You merely need to provide the system with what it needs, then get out of the way, the marshes in Louisiana were built from silts and clays LONG before you ever had engineers figure out "how to do it right"

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we arent going to wake up tomorrow or in ten years and be able to just start building the size of sediment diversions we need due to red tape bullshite. to get land building results on par with wax lake or atchafalaya delta, you would need at least a 100,000 cfs diversion structure. none are planned, or even on the drawing board.

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Actually it's not necessarily flow, but structure of the diversion that appears to play the biggest role in sediment transport. Also, I realize that diversions take time to build, but that is the solution. Attempting to stop the saltwater from entering the marsh...WHICH IT DOES NATURALLY...is stupid.

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we have to jump on it regardless of whether its the right order or not.

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This is just retarded. So the solution may be more detrimental than the problem long term...but we gotta do it now?

You sound like that skeleton Pelosi, "we have to pass the HC bill now to see whats in it."

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also, if we are talking land-building diversions, then it's a given that wildlife habitats will be destroyed before they are rebuilt. oyster beds will be silted over etc. etc. one way or the other, the habitat will be completely re arranged and it will affect animal numbers and behaviors.

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If you raid the shoals, you can enjoy watching the blue crab population decline, as well as others. I'm sure those coarse grained sediments you dredged will be have the correct porosity and chemical structure of the interstitial water to support a wholesale changing of the infauna and vegetation necessary for a stable marsh, also those coarse grained sediments aren't easier to erode than silts and clays that have coalesced naturally......

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if we restore most of the barrier islands, they all benefit from the one next to them, whereas if you restore one at a time (like we've been doing to the past 15 years), none of the others really benefit, and you are back rebuilding it a decade later.

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Any grain of sand put into the system is just that.....a gain for the system.

But it has to come from OUTSIDE the system.

Re-building barrier islands in response to this emergency would more than likely just be dredging sand from a couple hundred yards offshore and throwing it up on the beach. Nothing new added to the system. It may temporarily forestall oil intrusion into the wetalnds but would not be a permanent fix for the barrier islands.

Also, closing some of the bigger opennings like the barrataria bay waterway or the Caminada Pass is not feasible. You would close shipping lanes and the tidal prism is far too great for sand to withstand. Riprap might last a while, untill it sunk or the next hurricanne knocked them down.

i am with ya'll here. engineers may have created the problems, but engineering solutions are required nonetheless.

an auto mechanic messes up your transmission while its in the shop somehow...you don't hire a pastry chef to solve the problem.

the unfortunate reality is that someone will be pissed off in the end no matter what is done, whether it is a landowner, fisherman, river pilot, or plant scientist. if nothing is done, everyone will end up pissed off, so i am all for action.

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but that changes the further west you get from the river

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exactly. sediment delivery is nearly impossible now to lake racourci/ lake barre/ timbalier bay/terrebonne bay without a complete re-design of the whole area. you would have to route a flow from far away. if you want to create wetlands in that estuary, its basically going to all have to be artificial (dredging, marsh creation projects etc.). why not beef up the islands, there especially, to slow things down?

there is still hope, in theory, for breton sound and barataria.