“Serious problems cannot be dealt with at the level of thinking that created them.”  Albert Einstein

Echota Bend, Illinois River — Part 2

It is pointed out in “A Rehabilitation Manual for Australian Streams” that you learn more from failures than you do successes.  This is certain, but it is a hard pill to swallow nevertheless.  The failure of the root wads was due to the fact that the water got behind the root wads resulting in excessive erosive forces to the banks and the resulting bank failure.  This failure propagated downstream and undermined the downstream rock vein so that even though the vein was not moved, it sunk on the outer bank becoming flat and thus losing its functionality.

We had 3 options, do nothing and the project would surely fail, reconstruct the channel as designed using the existing root wads and it seemed certain to fail again, or reconstruct the channel as designed but with more rock vanes to turn the water away from the bank.

 John said “fix it,” so we did.  On February 5, 1998 we got in the water  and tried to salvage what we could of the rocks and rootwads and began to build the bank back out.  The material came from the inside point bar that had built out into the channel.  Then we brought in a bunch more rock and started building vanes.  We built 3 new ones and re-built the lower one.  We put the root wads we could salvage in between the rock vanes.  We completed the repairs on February 16, 1998.  The cost was less than $60,000.  The total cost of the project was therefore less than $145,000.

Salvage begins at Echota (Feb. 5-16, 1998)

Re-building the bank (Feb. 5-16, 1998)

Building more rock vanes (Feb. 5-16, 1998)

Functioning rock vanes (Feb., 1998)

Functioning rock vanes (April, 1998)

Echota Bend (Sept., 1998).

And then it started to rain...again.  In fact if you need rain, plan or do a stream project.  The fluvial geomorphic corollary to Murphy’s Law states that rain will come with restoration efforts.  On March 20, 1998 the average daily flow was reported to be 8,820 cfs.  Thus, the site received a flow in excess of bankfull 32 days after completion.  Photographs taken in April, 1998 show the project doing well.  The high-bank though only sparsely vegetated has not eroded a significant amount.

Echota Bend looking upstream (Sept., 1998).

Aerial photographs taken in September, 1998 show the channel to be stable.  You can also see how well the radius of curvature of the design channel matches the radius of curveature of nearby bends.  I didn’t measure any radii prior to the design.  I used Leopold’s relation between radius of curvature and bankfull width to determine the radius of the channel.  It’s amazing how well the relationship holds.

High bank at Echota Bend (Apr., 1998)

On October 7, 1998, the daily average flow was reported to be 5,670 cfs, which is slightly above bankfull.  Photos taken that day show the rock vanes functioning well and creating dead zones of low velocity and low shear stress in the near bank region.  Photographs taken at the site 10 days later show that the channel remained stable.

Bankfull event on October 7, 1998 (flow is below bankfull in the photos).

Vanes on October 17, 1998.

There were six events that exceeded bankfull in 1999, ranging from 4,800 cfs to 10,100 cfs.  On June 22, 2000 a flood came that closed down Highway 10.  The peak was reported to be 35,100 cfs.  I drove to Tahlequah the next day when the average daily flow is reported to be 20,400 cfs, to see it.  When I got there, the peninsula was covered in water.  I drank a couple of beers with Phil and decided to spend the night and watch it go down.  And it slowly did.

Hydrograph for Illinois River near Tahlequah (USGS 07196500)

Receding flood waters on June 23, 2000.

Receding flood waters on June 23, 2000.

By the next morning, the flow was back under bankfull and the rock vanes began to reappear.  It sure was a good feeling to see the structures intact and operating properly.  There have been several major flow events since that time and the project is still functioning as desired.  The main drawback at this point is that Phil and Cheryl will not let the riparian vegetation grow as it should.  They continue to mow and weed eat the site to maintain a “tidy” appearance.

Receding flood waters on June 23, 2000.

Receding flood waters on June 24, 2000.

Receding flood waters on June 24, 2000.

For the most recent photos of this site (as of July 14, 2004) go to Echota - 3.

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1504 Ann Arbor Drive

Norman, Oklahoma 73069-5363

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