Thompson Bend Riparian  Corridor Project – Power Point Slides, click on the thumbnail images to view a full size image.

 1.      Project Location

 2.      Dry Bayou Scour Hole Location – before damage was induced.   Note row of trees along river bank and lack of trees inland.  The arrow is pointing to the same location as the arrow in slide 1 and is the location where the Mississippi is attempting to break through.

2a.  In 1981 several barges went through a break in the private levee which fronted the river bank, accelerating the erosion process.

 3.     Same location as the arrows in the first two slides, but in 1983 after the river had initiated its’ attempt to cut across the neck of Thompson Bend.   The approximate distance from the river to the photo foreground is 0.5 miles. 
 

 4.      Aerial view across the neck of Thompson Bend in 1984 during a minor flood event.  The overland flow distance is approximately 1.5 miles, compared to 17 miles around the natural river bend.

 5.      Photo taken in 1985 illustrating the force of the water as it enters Thompson Bend.

 6.      Aerial photo taken in April 1985 showing extent of bankline damage.  Note reference point as the next slide shows an on ground shot of the actual over-bank scour. 

 7.      Typical overbank scour and erosion in 1985.  Estimates of 40,000 tons of top soil per acre were being eroded with each flood event.  Also note the large trees which had to be removed after each flood event prior to preparing the land for agricultural purposes.

 8.      Typical cotton-wood stakes planted by the local landowners in 1986 in the first attempt to stabilize the bend way.

 9.      Same stakes, but now mature trees, in 1990.

 10.   Aerial view prior to the Great Flood of 1993.  Note mouth of Bayou and tree screens across throat of bend.  Also note reference location.

 11.   Aerial taken during the Great Flood of 1993.  Not only was it a record flood in terms of height, the four month duration of the event was unprecedented.

 12.   Typical post 1993 Flood damage.  While the vegetation died, it provided valuable erosion protection.  But, subsequent flood events in 1994 and 1995 prevented natural re-growth and removed the dead trees, once again leaving the bend vulnerable to a catastrophe.  See next slide.

 13.   Same location, vegetation completely gone.

 14.   Aerial view with vegetation gone.  Refer back to slide 10 for a pre-flood reference photo.

 15.    This slide illustrates one of the positive aspects of the riparian corridors.  This portion of the screens planted in 1986 survived, and it is clearly evident that the trees catch massive amounts of drift, and the scour holes are actually stabilizing and in some instances showing signs of healing.   Actual velocity measurements taken during times of floods have shown entrance velocities into the tree screens are consistently reduced by at least 50% as they pass through the screens.   Maximum entrance velocities have been measured at 10 to 11 feet per second with Acoustic equipment.  The existing soil has a scouring threshold of 5 to 6 feet per second.  Thus, the 50+% reduction of the velocities through the screens reduces erosion and scour to almost negligible amounts.  After the last flood event in 1999, some landowners were complaining of deposition, a situation which has never happened in fifty years!

 16.   Land owners have also adopted the practice of leaving milo stubble in place after harvest.  The stubble greatly reduces over-.
bank erosion and is an excellent short term protective measure.

 17.   Year 2000 re-planting rows after Permanent Easement Acquisition was initiated by the Corps.

 18.    Future actions include continued acquisition of easements and planting and managing of Riparian corridors along this 30 mile reach of river.  The project life is perpetual, with the amount of yearly work directed at it being dependant on previous years river stages.  Some years substantial re-plantings may be required, but during periods of drought very little activity will occur outside of the selective harvesting of trees.   The perpetual easements and Memorandum of Agreement signed by the Corps and Landowners ensure that all will do whatever is necessary to ensure the successfulness of the project.   
19.   After the floods of the 1990's, the Corps made a commitment to stabilize the area and minimize future damages which could jeopardize the integrity of the navigation channel or the main line Federal, Commerce to Birds Point Federal Levee which skirts Thompson Bend.   This photo shows the relationship of the five Hillhouse Scour holes, which are located about 1 mile upstream of Dry Bayou, to the Federal Levee.  Note that if these scour holes would enlarge to the size of the Lower Dry Bayou Scour Hole, the Federal Levee which protects thousands of miles of land would be effected, if not destroyed.
  
20.  In addition, the Corps stabilized the existing scour holes with stone.  The scour holes were ringed with rock to discourage enlargement, and in the case of Lower Dry Bayou, the St. Louis District Micro-Models were utilized to design energy absorbing baffles to disrupt the high velocities to further minimize erosion.

21.  The Corps also committed to establishing Riparian Corridors (tree screens) along a 300 foot strip of high bank along the river bank of the bend and at certain key locations across the throat of the bend.  The Corps would purchase approximately 1000 acres in permanent restrictive easements along a 12 mile stretch of river.  On these easements, the Corps would establish Riparian Corridors where necessary, and manage existing Riparian areas to maximize their effectiveness to retard erosion.  In exchange, the land owners would get monetary compensation for their valuable farm land, and have first refusal right of any timber which could be harvested from the easements.  Numerous meetings and briefings were held to develop these plans.  Here Lester Goodin, left, president of the Thompson Bend Soil Management Association, meets with St. Louis District Engineer Col. Morrow(middle).

22.   This map shows the areas where easements have been or will be purchased.  The majority of the areas are locations where the individual land owners had initially tried to establish vegetation prior to the devastating floods of the 1990's.

(need image from Keith)

23.  These two photos visually show the effect tree screen can have on velocities.  The photo on the left is velocity data recorded with an Acoustic Doppler Current Profiler (ADCP) on the upstream side of a Riparian Corridor, and the photo on the left is ADCO data on the downstream or backside of the corridor.  Data collected during various flood events has continuously shown a 50% reduction in velocities, which in every case has reduced the velocities below the scour threshold of the soil.