Friday, April 23, 2021

Lower Grand River Flooding 2021

The Water Comes Faster, Deeper & Drains Slower … Residents Are Getting Sick And Tired It… 

Bayou  Pigeon  Fire Department  - Hwy. 75 Sand Bag Depot

Residents on Lower Grand River, Bayou Sorrel, Bayou  Pigeon, Pierre Part, Belle  River, and  Stephenville are getting sick and tired of flooding every time we get a hard rain. 

Imagine  living  with that every heavy rain means that the river is  going to rise and spill over it’s banks and flood your yard? 

Having to Elevate the HVAC, electrical equipment and  dealing  with sediment  and debris laden water.

Spiders and snakes swarm during these floods.

Real estate  studies indicate that the price of a residential property located within a flood zone  is significantly lower than an otherwise similar house located outside the flood zone. On average, a location  that has flooded lowers  property  value about 8%.  If a property is prone to flooding  from 15 – 60%

Cost from business interruptions, and on  and on.

The WEEK OF 4 / 12 / 2021 Flood waters were  moving down Lower Grand River to the Bayou Sorrel, Bayou  Pigeon (Iberville Parish). To  Belle River (Lower St Martin Parish), and Pierre Part (Western  Assumption Parish)   and 4 Mile Bayou & Stephenville flooding businesses, residences  and camps  along the Lower Grand  River and distributaries  and inundating low lying areas. 

There are real Iberville Parish residents  and campers dealing  with this to often.  People in Bayou Sorrel, Bayou  Pigeon, Pierre Part, Belle  River, and  Stephensville are getting sick and tired of flooding every time we get a hard rain

Pictorial Essay Of The Flooding April 2021


Bayou  Pigeon,LA. april 2021

Hwy. 75 Verrett’s Shipyard  @ Jack Millers  Landing 

Hwy. 75 Verrett’s Shipyard  @ Jack Millers  Landing 

Bayou Sorrel Hwy 75

Bayou Sorrel Hwy 75 @ Pete Kelly’s Crawfish Dock & Bait Shop 

Mike  U.  Hwy  75  Bayou  Pigeon …not  again…

Hwy  75 No Relief …

Having to Paddle  your boat  to your door every day, T Lloyd  Hebert

Bayou  Pigeon Phillips Camp April 2021 Indigo  Bayou Area

Camp  Sanguine April 2021 Bayou  Pigeon ,Indigo  Bayou Area

Bayou  Pigeon Clay  Coleman The  Shack April  2021

Bayou Pigeon - The Blanchard Home  at  Indigo Bayou  - April 2021 

Bryan Vaughn  - Boo’s Campground - Bayou  Pigeon Road -April 2021
Vehicle Traffic No Wake  Zone Barrier - Some People Won't Listen

St. Joseph Church - Pierre Part, LA. - Bayou  Pierre Part

Parker Conrad Flood Control Plan Map  c 1980

I Became Aware  Of This Plan /Map  4 /14 / 2021

I became interested in  writing  about this topic of Back water  and overbank flooding when I first saw this  map last week, I had not seen  this map before. In my 10 years of research in writing two books about the Atchafalaya Basin.

It was posted Posted on facebook, by Mr. Gregory Hedges of  Pierre Part, (a fellow  alligator  hunter). Greg posted to point out that the overbank flooding  that was  coming to our area was going to take some  time  to drain.

I  found the map extremely interesting  for  many reasons and  plus the fact I love looking  at old maps  and pictures  from the past.

1. The main reason, it clearly illustrates the boundaries of the Lafourche / Terrebonne  drainage basin, ie., A Picture Is  Worth A Thousand Words.  I wrote about how this new drainage basin came  about in my book,'Heritage of the Atchafalaya, A Natural and Cultural History of the Atchafalaya Basin.

2. It is easy to see how large this  area is and compare to the  size of the floodway. That it can capture a lot of rainfall.

After reviewing the map and realizing the story it was telling, ie.,  that it anyone could easily see it  was a  forerunner to  the current Bayou Chene Automated Barge Floodgate Structure.

I became interested in  researching this whole topic of backwater / overbank flooding.  

In my on line / internet  research  I quickly discovered,  this is a both a complicated  and  complex situation. No kidding...

Let Me  explain:

Relative to backwater flooding, it is COMPLICATED, but the things  that are causing the backwater flooding can be separated and dealt with in a systematic and logical way.

Whereas  the overbank  flooding along Lower Grand River is  COMPLEX.  

Complex issues are ones in which you can't get a firm handle on the parts /components of situation.  There is very little order, control, or predictability.  You  can't control the weather,  predict when extreme rain is going to hit and how much it is going to rain.  In my Six  Sigma training in an earlier career, I learned  it is best to  managed complex  situations until you have  lots of  long term data to make decisions versus trying to  solve it quickly.

Before there was an Atchafalaya Floodway 

Before the creation of the  Atchafalaya  Floodway and the USACE became responsible for allocating the waters in the annual flood pulse water in the  Atchafalaya Basin , water spread out and  went where it pleased and people could not do much  about it. 

Thus this latest round of exceptional heavy rain this past week (4 14 2021 over 13” in a 3 day period in Southwest  Iberville Parish area) That  is flooding Bayou  Grosse Tete  and over bank flooding  Lower Grand  River  with as much as 6 ft rise in  some places  would have not occured  before the  creation of the  floodway.

Which begs the question, Why is this extreme rainfall  and resultant overbank  flooding occurring more frequently, often several times in one year.  

Is it Climate change?

The climate is warming! the climate is cooling! We’re all gonna die! The answer is...all of the  above. Folks just need to chill out and understand that climate’s gonna climate, and there’s not that much we can  do  about it.

If you really want more information about  Climate Change  I suggest you read, “Dark, Cold Years Are Coming, So You’d Better Get Ready”.

Has it more to do  with the  Atchafalaya  Floodway System Than  Climate  Change!

Without a doubt, high water years in  the Floodway  and backwater  flooding are occurring more often.   I can remember my first recall of the back water flooding 50 years  ago,  1973 / 74.

May 1973 The Blanchard Home  At  Indigo Bayou; Compare to Picture  2021 above - Water Level Approximate;  No Different Than 50 Years Ago, Ie., 1973 To April 2021

Those years  are  still considered  highwater markers  for flooding  along the Lower Grand  River.

Just maybe it took  the 40 years between   1930’s  and 1973  for the manmade changes  to the  Atchafalaya Basin rivers, streams  and  landscape to reached an inflection point, severe backwater  and over bank flooding.

Personally , I am inclined  to believe, that the more frequent high water  in the  Atchafalaya  Basin and subsequent backwater and / or extreme rainfall  overbank flooding in the  Lower Grand  River Drainage Basin  is a natural outcrop of exponential growth and progress of mid  America and  poor or no water / sediment management. 
Not  the apocalyptic talk of climate change by  global warming zealots.

Since 1973, 1974, 1975 there has been back water flooding in years 1979, 1983,1997, 2002, 2008, 2011, 2016, 2017, 2018, 2019. 

Overbank Flooding  at Bayou Pigeon is not new.

Flooding at Bayou  Pigeon 1974

USACE AeriaL Photo 1974

USACE AeriaL Photo 1974

The Atchafalaya Floodway System  Levees

The Atchafalaya Floodway system was designed and built to protect agricultural areas and towns along and in the Mississippi river valley flood plain from flooding  by using the  flood way when necessary to contain excess floodwaters of the Mississippi and Red Rivers on their way south to the Gulf of Mexico.

The  core of the  floodway are two levees  approximately 15 miles apart.

The East Atchafalaya Basin Protection Levee (EABPL). The levee begins at the lower end of the east guide levee of the Morganza Floodway extends southward to and from Morgan City to the Avoca Island Cutoff, and includes the Bayou Boeuf and Bayou Sorrel locks. The length of this system is 106.7 miles. 

The West Atchafalaya Basin Protection Levee (WABPL). The levee begins near the town of Hamburg, where it joins the Bayou des Glaises fuse plug levee. It extends in a south and southeasterly direction to the Wax Lake Outlet at the latitude of the East and West Calumet Floodgates and thence eastward through Berwick to the Gulf Intracoastal Waterway. This levee extends 128.7 miles and connects with 3 miles of flood wall along the front of the town of Berwick.

I  do not believe the people who created the Atchafalaya Basin Floodway plan  and the Floodway itself in the 1930’s  at that time considered thought  of any consequences regarding  natural drainage  outside of the  new floodway when designing it. 

Unintended Consequences  - The Lafourche - Terrebonne Drainage Basin

One  consequence  of landscape  change  by building the floodway was the creation of a new drainage system, it is now known as the The Lafourche / Terrebonne drainage Basin. 

It falls naturally between the Atchafalaya Floodway East Atchafalaya Basin Protection Levee ( EABPL)) and the Mississippi River natural alluvial ridge.  It covers an area extending approximately 120 miles from the Mississippi River on the north to the Gulf of Mexico on the south. It varies in width from 18 miles to 70 miles.

Local Rain Fall / Water drainage east of  the floodway is totally between the EABPL  and Mississippi  alluvial ridge levees and has to drain through this  area.
I suppose it should have been considered  in the design phase how this new  drainage basin would interact over time with  the Atchafalaya  floodway.  

Such things as the effects of progress , like new  / more impervious surfaces like superhighways, streets and pavement, driveways, house roofs, shopping centers, Malls, etc.! 

A significant portion of rainfall in watersheds is absorbed into soils (infiltration), is stored as groundwater, and is slowly discharged to streams through seeps and springs. Flooding is less significant in these conditions because some of the runoff during a storm is absorbed into the ground, thus lessening the amount of runoff into a stream during the storm.

As watersheds are urbanized, much of the vegetation is replaced by impervious surfaces, thus reducing the area where infiltration to groundwater can occur.

When it rains the water no longer seeps into the ground, but now runs off into storm drains and then quickly into local streams / canals.

Couple this with inevitable  periodic extreme rain conditions at the same time as the Mississippi River annual flood pulse is passing through the Atchafalaya floodway and it seems like  someone should have brought up the question.

Today it is pretty obvious  that any extreme flow  in the  floodway overwhelms the exit of the water in  the Lafourche / Terrebonne  drainage Basin to the Gulf of Mexico  and Slows The Drainage, thus you  have extensive back water flooding.

I discuss this Lafourche drainage basin, in my book 'Heritage of the Atchafalaya Basin", on page 101.

Some Interesting Things About  the Parker Conrad Map / Plan, at least they are to Me …

As I studied the map, I realized, it purports to be an  alternative plan to the original USACE Atchafalaya Floodway  Plan, ie.,  ‘Project  Flood’ which I thought was I thought was written in  stone.

In my opinion it clearly is recognition that  the back water flooding that was occurring in the Lafourche-Terrebonne drainage basin was related  to extreme  water levels in the floodway.

If this was a serious proposal, it is  almost as 'mind boggling' as the  first plan was to create the Atchafalaya  Floodway in the  first place in 1928 / 29.

ie., this Plan called  for blocking / closing the Atchafalaya River at Morgan City !

Understand  the purpose of the Atchafalaya Floodway is control what is known Project  Flood  … Another great  flood  Larger than  the 1000 year flood of 1927

USACE Flood Control  Plan For Entire Mississippi River Valley
In  Louisiana  3  floodways with the  Lower Atchafalaya a vital part of moving the  flood to Gulf Of Mexico

Mind Boggling  proposals of the Parker Conrad plan :

This plan recognized / devised a plan   for the Backwater flooding in  the Lafourche / Terrebonne drainage basin over 40  years ago!  

The map identifies the bottleneck causing the problem,ie., Lake Verret and Grassy Lake drain into Lake Palourde drains via the Avoca Island Cut-off. 

A Bigger Outlet to the Gulf  at Wax Lake 

In the bottom left hand corner of the map, it shows  a proposed  spillway two miles wide, with plans to carry 100 % of Atchafalaya river flow under normal, I assume   that means low water  conditions.

Background  info on The Wax  Lake Outlet 

Wax Lake was a lake in St. Mary Parish, Louisiana that was converted into an outlet channel, the Wax Lake outlet, to divert water from the Atchafalaya River to the Gulf of Mexico. 

The Wax Lake Channel was created by the United States Army Corps of Engineers in 1942 to divert 30 percent of the flow from the Atchafalaya River to the Gulf of Mexico and reduce flood stages at Morgan City, Louisiana. The  channel is approximately 15 miles long that begins at Six Mile Lake (and the "Charenton Drainage and Navigation Canal", that began at Bayou Teche in Baldwin, LA.

The Avoca  Island  Cutoff / Bayou Chene area, has been a major conduit for  this backwater flooding. 

Back water  flooding through  Bayou Chene is enhanced & facilitated  by a  navigation channel maintained  20 ft deep and 400 ft wide.

Avoca Island / Bayou Chene   Channel

2021 - Current  Project At Avoca Island Cutoff / Bayou Chene To Reduce Backwater Flooding

Gov. John Bel Edwards Announced in 2020 Construction will start on Permanent Floodgate at Bayou Chene in St. Mary Parish.  The projection is underway at the time of this writing.  

High water events in the Atchafalaya Basin, have precipitated  backwater flooding in the parishes of St. Mary, Terrebonne, Lafourche, St. Martin, Assumption.   

The Louisiana Coastal Protection and Restoration Authority (CPRA) and St. Mary Parish Levee District (SMLD) are overseeing construction of the automated barge floodgate.

Diagram of Backwater flow through  Avoca Island  Cutoff  / Bayou Chene 

Artist Illustration Completed  Automated Barge Floodgate

Diagram of water flow to gulf when Automated Barge  flood control structure is  closed

The flood pulse eventually reaches  Lake Palourde  and is diverted through Amelia and  Bayou L’ourse and out  to Bayou Black and the Gulf of Mexico.

Problem Solved  For Bayou  Sorrel, Bayou Pigeon, Likely Not

Problem #1 Water / Sediment Management...

Lower Grand River in Iberville  and Iberia parish  have experienced rapid and substantial amounts of sediment deposition since the 1960's.  Particularly between the Bayou  Sorrel  Locks & Belle River. 

Severely aggraded and silted up areas of the Lower  Grand River  channel are holding back the water flow especially around the Bayou Pigeon Pontoon Swing bridge. 

Dredging  and channelization of Lower Grand River has not occurred  since the 1920’s.  In fact it may have not been dredged  for over 100 years.


Documentation of last dredging in  Lower Grand  river

Barge Traffic on Lower Grand River at Bayou  Pigeon c 1950's or early 60's

Some local residents  say that  since the Grand River at Bayou Pigeon is no longer part of the Alternate  route of the Intracoastal waterway, ie, since the Bayou Sorrel  Lock.  The lack of barge traffic  does not help scour to keep channel open anymore.

Problem #2 - The Pontoon Swing Bridges On  Lower  Grand  River

The Bayou Sorrel pontoon-style bridge, built in 1964, carries La. 75 over Upper Grand River and Bayou Sorrel in Iberville Parish. 

Lower Grand River Bridge, Bridge Recall # 054480 constructed in 1957 /58 opened in 1959.  Carries traffic  from Louisiana Hwy. 75  to Highway LA 997) over Bayou Pigeon/Lower Grand River, Plaquemine, Iberville Parish, LA

When the Lower Grand River water level gets high, the bridge master pumps water into the Bridge  barge  to lower it into the water column so it is level enough for vehicular traffic to cross; otherwise the bridge would be too high above the ramps.  As a result the sunken bridge restricts the water flow even more, and especially at a time when maximum drainage flow is needed to allow the floodwater to drain downstream.

It has been said that the water level  elevation  on the north side of the  Bayou Sorrel Pontoon Bridge and the  south  side of the bayou  Pigeon Pontoon Bridge is as much as  11”.

If that difference can be validated, it means they are an significant impediment  to rapid drainage.

Which begs the question why the bridges can’t be in open position in the wee hours in the morning 11 PM to 4 AM except in cases of emergency.  There is essentially no barge traffic in The lower Grand river below the Bayou Sorrel lock

There are pontoon bridges at Belle River  and Pierre Part.

Problem# 3 - Lock  Structures 

Bayou Sorrell Lock on Lower  Grand River

Bayou Sorrel Lock & Dam

Lock structures have guidelines by water stages on when they cannot allow Boat traffic or leave open the lock gates. Boat traffic is ceased  at 6.5 ft at the Bayou Sorrel  Lock gauge. 

Even though  boat traffic  is  stopped the  lock gates remains  closed. By opening the  lock gates,  it seems logical it would let some of the high water into the  Atchafalaya  Floodway, where there are no residents.

I presume the USACE has data to say the  flood pulse flow inside floodway  would overwhelm the Lower Grand River flow  and cause back water flow. 

An alternative proposal to  leaving Lock gates open to drain the water, is a  pump station somewhere north of Bayou Sorrel  lock to pump water over the levee into the Atchafalaya Basin during overbank  flooding. 

An alternative proposal to  leaving Lock gates open to drain the water, is a  large volume pump station somewhere north of Bayou Sorrel  lock to pump water over the levee into the Atchafalaya Basin during extreme rainfall  and  overbank  flooding. ( probably the most effective cost technology)

“Which brings to this point”

Will  the Bayou Chene Automated Barge Flood Gate alleviate all, most or some of the extreme Rain Water over bank flooding below Jack Millers Landing , through Bayou Sorrel, Bayou  Pigeon? 

Without addressing Water / Sediment  management and the pontoon bridges  situation and not being able to move  some of the high water out of Lower Grand  River  to the Atchafalaya Floodway. 

I think the answer is at best some relief  and most likely very little to none.

The water will still go out very slow.   Even if the  annual Atchafalaya Flood Pulse is  average.

Just saying …  We are still screwed !

Overbank flooding is a threat to the sustainability and growth of Bayou  Pigeon. The Bayou  Pigeon Heritage Association can be the voice for our local community as we push for flood protection that is critical to our survival and that will help us continue to improve our community and the ‘Down The Bayou’ part of  Iberville Parish.

The Eastern Gateway  To The  Atchafalaya



Bayou  Pigeon The Only Authentic Cajun Community In Iberville Parish

Aim Straight


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