Mississippi River wing dams

[Indefatiguable]

Hey folks,

I'm planning on taking my formosa 36 down to the fl keys from the great lakes region this fall.

Was hanging out with my grandpa and he mumbled something about wing dams. When I said "what?" He replied since I had to ask I'd better read up on it.

I draw around 4', use navionics and openCPN side by side (erring on the shallower chart), and have never done this trip before.

Anyone have any insight beyond what I can Google? Apparently they (the wing dams) are often submerged?

Any/All comments, advice, random nonsense welcome - and Thanks in advance.

[Constellation49]

Not trying to slow you down, no pun intended, but adding water wings to your vessel will not increase the speed as you would suspect. Speed through water is a calculation that is attainable with the correct datum’s input into the equation.


Terminal velocity is the maximum velocity (speed) attainable by an object as it falls through a fluid (air is the most common example). It occurs when the sum of the drag force (Fd) and the buoyancy is equal to the downward force of gravity (FG) acting on the object. Since the net force on the object is zero, the object has zero acceleration.[1]

In fluid dynamics an object is moving at its terminal velocity if its speed is constant due to the restraining force exerted by the fluid through which it is moving.[2]

As the speed of an object increases, so does the drag force acting on it, which also depends on the substance it is passing through (for example air or water). At some speed, the drag or force of resistance will equal the gravitational pull on the object (buoyancy is considered below). At this point the object stops accelerating and continues falling at a constant speed called the terminal velocity (also called settling velocity). An object moving downward faster than the terminal velocity (for example because it was thrown downwards, it fell from a thinner part of the atmosphere, or it changed shape) will slow down until it reaches the terminal velocity. Drag depends on the projected area, here represented by the object's cross-section or silhouette in a horizontal plane. An object with a large projected area relative to its mass, such as a parachute, has a lower terminal velocity than one with a small projected area relative to its mass, such as a dart. In general, for the same shape and material, the terminal velocity of an object increases with size. This is because the downward force (weight) is proportional to the cube of the linear dimension, but the air resistance is approximately proportional to the cross-section area which increases only as the square of the linear dimension. For very small objects such as dust and mist, the terminal velocity is easily overcome by convection currents which prevent them from reaching the ground and hence they stay suspended in the air for indefinite periods. Air pollution and fog are examples of convection currents.

[Indefatiguable]

No there's dams in the river that only extend partially from the shore. Not boat appendages, underwater (or above water) structures.

I have no interest in trying to foil in my 18000lb ketch. Wait, maybe if I put little rocket nozzles on the wing tips? J/k

[AKA-None]

Stay well away from wing dams unless you are in a fishing boat and unless you really don’t like your keel

[scherzoja]

You might want to consider using the Tombigbee waterway to Mobile instead of the Mississippi. I've never been down either, but I recon the Mississippi would be a bit more difficult with the wing dams, tug traffic, and stronger current.

Watch out for the Chain of Rocks just north of St. Louis.

https://mississippiriverwatertrail.o...hain-of-rocks/

[tamicatana]

As mentioned, most pax travel via the Tenn-Tom. Plan also for having the mast trucked; I don’t know where in the north the facilities are, but in Mobile, Turner Marine specializes in installation. I’ve been there to watch the season progress; it’s quite something to see the trucks loaded with masts and the crew handling them

[Bullshooter]

I am from Louisiana and have been down the river many times. What your grandfather was referring to are structures in the river south of Venice. They should not be a problem if you do not approach the sides of the river they extend from. Check them out on Google Earth. The river is very navigable, but there is a lot of commercial traffic so that would be more of a concern.

[Manateeman]

A lot of commercial oil field boats enter the Mississippi almost at the end. It’s a place called the jump cause you jump into the River. One night at the jump, I saw three unlit runaway barges hit the offshore supply boat who had just entered the river ahead of us. They never saw it coming. A new 160’ steel boat. You couldn’t believe the damage. One barge had climbed right up on the stern of the supply boat. They were lucky they didn’t sink. The river is dark, cold, full of junk and it’s all flying along with a power you won’t believe.
The river kills people all the time. Do not underestimate the danger.
Captain Mark

[valhalla360]

Originally Posted by scherzoja

You might want to consider using the Tombigbee waterway to Mobile instead of the Mississippi. I've never been down either, but I recon the Mississippi would be a bit more difficult with the wing dams, tug traffic, and stronger current.

Watch out for the Chain of Rocks just north of St. Louis.

https://mississippiriverwatertrail.o...hain-of-rocks/

If you take the river system south, you have to take the Mississippi from North of St. Louis to the Ohio River. At Chicago, there are a couple of routes that get you to the Illinois River which ends just north of St. Louis. Then about 200miles on the Mississippi to the Ohio. Then you have the option to go up the Ohio to the Tenn and connect via the Tenn-Tom to the Tombigbee and pop out at Mobile. This is the preferred route for most cruisers as the Mississippi has very limited facilities for pleasure boats south of St. Louis and the current/tow traffic gets pretty wild.

North of St. Louis, there are many dams on the Mississippi which limit the size of tows and keep the currents more reasonable.

South of St. Louis, the river flows free. Tows get massive (bigger than ocean going oil tankers). The currents can get very fast (ever dock at full throttle to offset the current?).

With no regular dams, the corp of engineers have built wing dams. These are basically short breakwalls that extend partway out into the river and keep the flow centered and strong. This helps flush the silt out of the main channel without dredges, so it stays open for shipping even during low water.

The river level can and does vary greatly depending on the time of year and upstream precipitation (15-20ft variation over the year is nothing unusual and in flood conditions even more).
- In low water periods, the dams may be completely exposed and easy to see.
- In high water periods, they will be under water. If only slightly under, you may see a standing wave but if they are deeper, you may see nothing.
- Also debris (like whole trees) tend to collect behind them, so even if you make it over the dam a large branch may be waiting to skewer your hull..

Very questionable trying to just go over them.

You will want a boat with a reliable engine and a motoring range of at least 250miles. You need to be able to go where the tows tell you to go when they tell you. They will not be able to maneuver around you. Likewise, you want to be good at close quarters work as you will need to do a lot of it in Locks and many marinas are up tight side channels.

Now that I've put some fear of God into you, it's actually a great trip and very interesting. Highly recommend it.

PS: If you get mixed up with the "chain of rocks", you were seriously not paying attention.

[Rumrace]

So you plan on heading south via Chicago to FLA? You need to take your mast down any route but the St.Lawrence. Just south of Chicago. There are two branches in Chicago. One is a no go the other is direct. If you contact the Great Loop folks they have massive history and data on any segment of the loop.
You’ll love Lake Michigan ports on Michigan coast line. Holland is a must see.
Alternatively Oswego New York, of Lake Champlain which is prettier for awhile.
Loopers go clockwise and counter clockwise. They use the Trent Severn mast down 45 locks from Honey Harbour Georgian Bay to Trenton Lake Ontario. 5’ draft just make it. Several narrow passages and always a few power boats don’t understand while you need the middle.
The wing dams I’ve just read about but ive also read they have no issue getting boats through. I suppose it’s like waiting for a swing bridge. I think they are to control swells.

[Rumrace]

I just read Valhalla 360 right up.thanks it’s a a great write up. You found yourself a looper. Enjoy the trip.

[Cheechako]

Originally Posted by Constellation49

Not trying to slow you down, no pun intended, but adding water wings to your vessel will not increase the speed as you would suspect. Speed through water is a calculation that is attainable with the correct datum’s input into the equation.

You know you're on CF when........

[Manateeman]

I just got a few pairs of water wings for my manatee crew because the self inflating life jackets would pop open too easily from spilled beer.
The crew refused to wear them so I have no data on how this changes boat speed.
Mark

[donradcliffe]

I did the Mississippi from the Illinois down to the Ohio on a GB42 which drew 4.5 ft. Water level was low enough that the 9 ft draft towboats/barges were being held up, but we could go through. Never had a problem with the wing dams. They were on the charts.

We decided to do the Tenn Tom because it is more scenic and less industrial. If I was in a hurry I would have taken the Mississippi.

Learn what one whistle and two whistles mean ESPECIALLY WHEN OVERTAKING. Generally the towboats want to be outside on the turns so they don't accidently crush you into the bank. AIS is a huge help to see what is coming around the next corner.

We ran the GB at 7 knots, 6 down the Mississippi, to save fuel. Flank speed was 8.5-9, but I only used it once to make a lock opening.

[Jammer]

I will break with CF tradition and actually answer the question in the opening post.

I kept my sailboats on the Mississippi (in Lake Pepin) for four years and have taken side trips up to the current head of navigation in Minneapolis, and have been a little ways downstream and on tributaries. I have also explored parts of the Mississippi in fishing dinghies and have explored the Mississippi on SCUBA.

On the portion of the Mississippi from Red Wing to St. Paul, there are extensive wing dams. The ACOE charts show the approximate original positions of the dams when built in the early 20th century. The dams are essentially piles of rocks that, at one time, funneled the flow into the main channel. The idea was to improve stream velocity in the main channel and reduce sedimentation there. It didn't work, and the present system of large dams and locks replaced it and flooded the wing dams, so that they were typically a few feet under the surface of the water.

Downstream portions of the Mississippi also have wing dams, according to the charts, but I haven't been there and can't comment based on personal experience. I would expect to find that the situation there is similar, in those broad, shallow, meandering areas that have low flow.

The wing dams have been moved around by ice, debris, barges, etc. over the years and are generally lower in the water and downstream of their charted locations. But the charting was never 100% accurate, and only really serves as a rough guide to the portions of the river where wing dams may possibly be encountered outside the edges of the 9' official channel.

Because they are point obstructions they do not reliably appear in crowdsourced depth data supplied by Navionics and others.

They remain a hazard to navigation for smaller boats. Barges as a rule just knock them over when they hit them. It's only a pile of rocks.

When traveling the Mississippi or any of the inland rivers, you would want to stay within the marked channel unless you have made your own survey of the river bed (as you might if you are trying to anchor outside the channel) unless you are willing to accept some amount of risk of hitting a wing dam (or tree or etc). This is especially true in areas where wing dams are charted. You may, in fact, want to snorkel the area where you are anchoring to confirm that the boat will not drift into a wing dam while swinging on its anchor, and I have done this.

Alternatively you can proceed slowly and be alert for any indication of contact, and figure that you'll probably get away with nothing more than a few scratches. The smaller boats I use for river exploring (a canoe and a 14' aluminum utility boat) have accumulated some scratches and some nicks on the propellers.

River navigation involves accepting a certain amount of risk of damage from contact with submerged debris. The prop is most vulnerable. You would want to take off your expensive folding or feathering prop if you have one. Might not be a bad idea to carry a spare prop.

Hope that helps.