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Your memory is correct. I think everybody along the Mississippi and Atchafalaya river needs to be aware of this situation and have plans in place now. They are predicting four to five days of rain in the upper Ohio River basin starting this weekend. All of that will run off almost immediately due to saturated soils in the area.Quote:
Originally Posted by Cajun90
That is on top of the major flooding they are already dealing with. A lot of that flooding is due to them not letting more water flow downriver due to the high river stage we are currently at.Quote:
Originally Posted by HelmutVII
This will be an interesting next few months. It may be ok in the end, but it is definitely lining up to be a catostrophic spring for the Lower Mississippi River.
Great book. Bayou Farewell by Mike Tidwell is fantastic as well.Quote:
Originally Posted by gorcajun
This erosion (ditch by my house) is from average current after rainstorms when the vegetation was removed with Roundup.Quote:
Originally Posted by HelmutVII
It got way worse than that because the lawn care company kept spraying the edges, and the dirt kept falling in. The State eventually applied asphalt before the road caved in.
I can only imagine the speed of dirt loss for a levee without vegetation.
It's not just the roots that protect, the blades of grass under water current act like roof shingles protecting the dirt.
I image the real damage begins when the vegetation on the banks of the river begin to die and decay from being under water for too long.
You have intuitively discovered the existence and significance of Mannings roughness coefficient (Mannings "n") without realizing it.Quote:
Originally Posted by Turbine
Grew up downstream from a sugar mill and Breaux's Baycraft on the Teche. Anyone that grew up on the Teche, Vermillion or other waterway will tell you erosion is a fact of life. It is a labor of love the work we've done to battle even simple nature. Between concrete fill to purchasing cypress seedlings from USL years back, we've maintained the yard to a degree our neighbors who are not proactive have multiple feet less of yard. We even have it slightly bowled, so much so in the 2016 flood we gained a good inch of sediment according to the property marker pin we use to measure such. That was a natural event.
Another snow/rain event over the Mississippi/ Ohio river basin this weekend will put additional water in the drainage basin that will eventually pass to the Gulf of Mexico one way or another.
Current by pass rates down stream of the ORCS are 442000 cfs and the water is rising a bout 1.0 foot per day. Request flow rate and stream level NAVD. (North American Vertical Datum) when you get to the link below.
https://waterdata.usgs.gov/la/nwis/u...20,63160,00060
Mississippi River at Knox Landing is rising about .05 foot a day. They don't publish flow rates for this station for some reason.
https://waterdata.usgs.gov/la/nwis/u...20,63160,00060
Mississippi River at Bonnet Carre is rising about a foot in four days as opposed to about a foot in two days before they opened the spill way.
It has been at or above flood stage for about a month.
Vicksburg is passing 1,830,000 cfs and water levels are rising about 1 foot in two days
https://waterdata.usgs.gov/la/nwis/u...20,63160,00060
Current prediction is for it to reach 51.0 on Wednesday and stay there for about a week and start to recede. We shall see. I still haven't seen anything regarding openining of the Morganza Spillway.
Go here for information about all the stations on the Mississippi river reporting stations. It is kind of quircky and I would not attempt to go there on a mobile devise.
https://water.weather.gov/ahps2/glan...riverid=203833
It needs to stop raining in the Mississippi and Ohio river basins long enough for the river to go down before snow melt.
Northern California has has a very wet and snowy winter. Watch the weather there and figure two to thee days later it will be over the central to eastern portion of the US driven by the jet stream. If they keep getting rain and snow then we will see the result of it after the runoff routs through the Mississippi River. I suspect we will see a series of crests and valleys on the Mississippi up until June.
If the Corps and the State will get going on adding more Mississippi River diversions flowing at will during high water south of NOLA into the marshes and let at least a small amount flow down Bayou Lafouche maybe the sediment will get put to good use. Try to mimic pre 1927 without putting human lives at risk. And if Morganza is not opening why not divert more flow into the Atchfalaya R. then kicking more into the Teche-Vermilion diversion during high waters?
There is the Caernarvon diversion just downstream of New OrleansQuote:
Originally Posted by Duckster
https://waterdata.usgs.gov/usa/nwis/...95124089542100
But they pass only about 400 to 600 cfs. Not much but there has been some delta formation at the outffall. They could pass more but you would have to ask the oyster fishermen why. Just sayin.
Subsidence in that area is in the order of about 1.5 cm per year. (1 foot in twenty years) So they need to make up that amount just to stay even. Kind of hard to do that with 400 to 600 cfs. of decant water from the Mississippi.
The Wax Lake outlet and the Atachafalaya have really nice delta formations. The source is decant water from the Mississippi at Morganza. the one to the west is Wax Lake outlet and the one to the right is the Atchafalaya.
One of my favorite classes a hundred years ago, taught by a guy named Reese, was Louisiana Geography. One of the many interesting subjects I enjoyed in his class was the discussion of the Army Corp of Engineers levee system and its effects, pro and con (mostly con), on S. Louisiana's coastal marshes.Quote:
Originally Posted by HelmutVII
The Mississippi River, before it was "tamed", swung back and forth across S. Lousiana over the eons building marshlands in its path. When the mouth of the river swung to the west, former beachheads in SW Louisiana soon became cheniers as hundreds of yards of new marsh formed in front of them from the sediment being dumped into the relatively shallow Gulf. When the river swung back to the east, a new beachhead in the form of a chenier appeared and hundreds of years later with another major flood, the river changed its course once again and the process repeated itself.
Just look at any Louisiana map and you can see the old deltas.
Today, with the river's course harnessed, most of that sediment is no longer making its way westward and is instead being dumped off the contintental shelf into deep water. I think Wax Lake Outlet is about as far west as Miss River sediment now makes it via the Morganza Spillway.
Loved that class. One of only two I didn't have to take the final. :)
Go to my post 35 in this thread where I try to the best of my ability to describe land formation in Lafayette parish. the link to the NRCS soil survey has tons of very interesting information. Go to post 106 where I try to describe the location of the Coteau Ridge.Quote:
Originally Posted by Cajunfanatico
The maps in the NRCS soil survey will show ancient Ox Bows and river scars if you know what to look for.
You posted while I was editing.