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Started By
Message
re: Bonnet Carre Spillway to open Thursday
Posted on 3/6/18 at 12:24 pm to LSUFanHouston
Posted on 3/6/18 at 12:24 pm to LSUFanHouston
The Corps maintains a shipping channel (42'? 45'?) from the mouth of the river to BR. The area of heavy shoaling is north of BR and just south of ORCS. It definitely isn't being dredged because large ships don't go that far north.
1
Posted on 3/6/18 at 12:30 pm to LSUFanHouston
IIRC, a good portion of it is due to the straightening of the river which took place in the early-mid 1900s. Prior to that, the river was considered to be in "dynamic equilibrium" overall. Meaning that the channel may shift but no large scale bed aggradation or degradation was taking place.
The meander cutoffs led to a steeper river and tipped the balance of the sediment transport dynamics of the system.
I believe that the bed in the lower portions of the river are aggrading with portions in the middle considered transitional and in upper portions (above Memphis?, dont really remember) the bed is actually degrading.
So the upper portion is lowering while the lower portion is rising while the river tries to get back to a more stable slope.
The meander cutoffs led to a steeper river and tipped the balance of the sediment transport dynamics of the system.
I believe that the bed in the lower portions of the river are aggrading with portions in the middle considered transitional and in upper portions (above Memphis?, dont really remember) the bed is actually degrading.
So the upper portion is lowering while the lower portion is rising while the river tries to get back to a more stable slope.
Posted on 3/6/18 at 12:33 pm to White Roach
quote:
The Corps maintains a shipping channel (42'? 45'?) from the mouth of the river to BR. The area of heavy shoaling is north of BR and just south of ORCS. It definitely isn't being dredged because large ships don't go that far north.
That's what I thought. So I'm not sure what impact this shoaling has on the river as it passes the carrollton gage, but it can't be much.
So the idea that these openings are happening more often "because the river bed rose 5 feet" is bunk.
Posted on 3/6/18 at 12:37 pm to Spankum
quote:so how did these oyster beds survive before levees?
quote:
Bonnet Carre = oyster bed killer
exactly what I thought when I read this. I understand that lots of oyster beds were killed by the last opening and I would expect this round to finish them off.
Posted on 3/6/18 at 12:40 pm to LSUbase13
quote:improve it.... and it's entire basin
What does this ultimately do to Lake Ponchatrain?
Posted on 3/6/18 at 12:40 pm to CroakaBait
quote:
Bonnet Carre = oyster bed killer
nah...there are plenty of fresh water diversions that do a pretty good job of this on their own
Posted on 3/6/18 at 12:41 pm to choupiquesushi
quote:
so how did these oyster beds survive before levees?
Well, you didn't have a torrent of water being funneled at a high rate in a 1.5 mile width into the lake.
You had more gradual flooding... and even if some if this water made it's way to the lake, it wasn't at the densities you have with the spillway.
With the exception of crawfish, the spillway is an ecological disaster. But... it prevents flooding downstream. And property > oyster beds.
Posted on 3/6/18 at 1:17 pm to LSUFanHouston
quote:
Well, you didn't have a torrent of water being funneled at a high rate in a 1.5 mile width into the lake.
You had more gradual flooding... and even if some if this water made it's way to the lake, it wasn't at the densities you have with the spillway.
With the exception of crawfish, the spillway is an ecological disaster. But... it prevents flooding downstream. And property > oyster beds.
What was the overall flow into the Lake P basin before levees...
disagree on the ecological disaster thing - the best years I have had in the Lake P related areas have all been spillway years...
and wasn't it like 60 years in the 1800s that water free flowed through the bonne carre crevasse?
Posted on 3/6/18 at 1:22 pm to Tarps99
quote:
I agree and some equivalent should be built on the west side.
Call me kooky but using the Wax Lake outlet as a model, a spillway or outlet channel should be built into Lake Des Allemands to freshen up that basin and bring some sediment down into Barataria Basin.
Probably going to need some levees for the low spots and Pleasure Bend.
That's a pretty damned good idea.
Posted on 3/6/18 at 2:26 pm to udtiger
I know it is. I came up with it after looking at a map when some one proposed something called the Bayou Lafourche Conveyance channel to bring water from the Mississippi without having to use the current channel of Bayou Lafourche. The proposed cost was astronomical for the conveyance channel.
But that was before someone thought to use a pipeline for the MidBarataria project.
I still like my idea better as it has 3 functions is brings a new delta building process in a heavily damaged ecosystem, brings fresh water to the Baratria basin and it lessens the impact on seafood as the water has a chance to spread out instead of dumping fresh water where it has been salty for years. And it gives nature a chance to dictate where it goes because of the wide area to flow through.
The only straight jacket is Hwy 90 and Bayou Des Allemands, but that will one day be a bridge with I49 in the next 100 years.
But that was before someone thought to use a pipeline for the MidBarataria project.
I still like my idea better as it has 3 functions is brings a new delta building process in a heavily damaged ecosystem, brings fresh water to the Baratria basin and it lessens the impact on seafood as the water has a chance to spread out instead of dumping fresh water where it has been salty for years. And it gives nature a chance to dictate where it goes because of the wide area to flow through.
The only straight jacket is Hwy 90 and Bayou Des Allemands, but that will one day be a bridge with I49 in the next 100 years.
Posted on 3/6/18 at 2:32 pm to choupiquesushi
quote:
wasn't it like 60 years in the 1800s that water free flowed through the bonne carre crevasse?
I believe in the 1927 flood there was a major levee crevasse at Bonnet Carre, or at least nearby it. I'm pretty sure that had a major impact on the spillway site selection. Construction began just a few years after the "Great Flood of 1927".
Posted on 3/6/18 at 3:15 pm to Tarps99
I didn't know I wanted this but I want this.
Posted on 3/6/18 at 3:20 pm to Tarps99
What do you mean by using a pipeline for the Mid-Bar project?
Posted on 3/6/18 at 5:21 pm to AliBahBah54
I must have gotten another project mixed up with it. Pre-oil spill money days Lafourche, Jefferson and Plaquemines was talking about or did a slurry pipeline to do similar work as Mid Barataria but with pipeline.
You have to realize most projects exist in this state on paper. Just about as much money is spent on planning future projects that have little to no funding in the construction phase.
You have to realize most projects exist in this state on paper. Just about as much money is spent on planning future projects that have little to no funding in the construction phase.
Posted on 3/6/18 at 6:09 pm to White Roach
White roach original bonne carre crevasse was in 1800s.
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