Wabash River cuts a new channel
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The June, 2008 flooding on the Wabash created a new channel and a new island on the lower Wabash River. The force of the high water against a bend at Mackey Island broke through the bank and cut a shortcut toward the Ohio River. Mackey Bend is a huge bend in the river located only a few miles from the mouth of the Wabash at the Ohio River. This is a very important event. Besides the fact that the property owners have lost access to their farmland, there are other notable affects.
1.) If the new channel stays (and probably will) this new island will be the largest on the Wabash River. The island is about 1,700 acres of land.
2.) The new channel will likely continue to be scoured in subsequent high water since the river will follow the flow of least resistance. If this happens, the old channel will be captured by the new channel and the old channel will begin to silt up from the downriver side to the upriver side of the island. This process could take a several years but eventually the old channel may close up completely and the Wabash River will be 6 miles shorter (see diagram below). The new island will no longer be an island once the old channel is partially filled with silt (forming an oxbow lake.
3.) Boaters traveling this section of the river should be aware that the old channel may become shallower immediately as a great deal of the water may be diverted to the new channel. Also be aware that the current in the new channel will likely run swifter.
There are very few things that can prevent this natural cut-off from eventually becoming the main trunk of the Wabash River. Since the cut-off began on an outside bend, the blunt of the river current will continue to bombard the same area and Mackey Island will also continue to divert water in the direction of the new channel. The U.S. Army Corp of Engineers could possibly fill in the new channel during low water, then shore up the bank with revetment (rocks), but they have already stated that this will not be done because they had no levee there to begin with and that the cut-off is a natural event. As much as I feel for the farmers who cannot access thier property, I agree that nothing should be done. This is something that rivers do and always have done. When looking at satellite views of the river it is easy to see the many oxbows that were once river channels. Old bends disappear and new bends form. Building levees in this area would be a mistake. This is a natural flood plain area and more levees will cause the river to rise even higher upstream, causing even more flooding in areas that now do not flood.
Mother Nature, of course is not totally predictable. She could silt up the old bend from the upriver side of the cut-off, as happened at Grayville, Illinois in 1986. Another possibility will be that enough trees and other debris, along with sand will be forced into the cut to close it back up. The speed at which the changes described take place can vary depending on river conditions.
I will be traveling to this area by boat soon and have a better assessment of what could and has occurred. I will report my findings on this page. Below are aerial photos kindly provided by Holly Wildt of Evansville, Indiana and an illustration taken from the Wabash River Guidebook that shows the new cut-off. More photos will be added when I return. Please check back as I update this historical event.
The changes in the river will be made in the next edition of
the Wabash River Guidebook, which will be this fall. To supplement the books
that many already have, click the link below to open a pdf file of the updated section 35 page. If anyone has additional information, please contact me at iwahay@gmail.
July 15, 2008. Having just returned from a boat trip to the new Wabash River channel, I have filed the following report and photographs:
I knew from the aerial photos that the cut-off was fairly wide but was impressed by just how wide it is and how fast the current was flowing into the new channel. My first approach to the cut-off was from upriver, and as I got closer to Mackey Island the current increased significantly. At the head of Mackey Island the fastest water was being drawn to the left of the island and into the new channel.
As I entered the new channel my depth finder was showing a 6 feet depth and the GPS was showing the current in the channel to be running at 6.3 MPH. The banks are very high and were still eroding. I saw large chunks of land falling into the water as I passed through the cut-off. A tall steel pipe stands in the middle of the channel near the lower end of the cut-off. This appears to be what is left of an old oil pump that was once located on land. It was fascinating to know that I was drifting through this large, swift body of water that was farmland only a few weeks ago.
The new channel is less than a mile long and becomes wider as it flows back into the neck of the old river bend. At first is appeared that there was a tree still in place in the center of the lower end of the cut-off but then I could see that is had actually been dislodged from where is had been before the cut-off and was grounded at this location (for the time being).
The lower end of the cut-off is less than a mile from the Ohio River. While heading down to the Ohio River from that point I discovered a new sandbar right in the middle of the Wabash River. I found this, as I have often done, by running aground on it. After breaking loose, I discovered that the deepest water is along the left bank. An interesting new feature on the Ohio River is the new man-made beach, just above the mouth of the Wabash River. This was formed by the U.S. Army Corp of Engineers dredging. Since the new cut-off carried so much sand into the Ohio River, the navigational channel on the Ohio became to shallow for commercial traffic and was closed for a time while they pumped the sand through a pipeline and near the Indiana shore. The "dredge spoils" as it is called, became a new beach.
The next thing to explore was the condition of the old channel. This is the six-mile bend that the new channel cut off. The average channel depth in this bend was 9 feet, being deeper at the lower end. This is actually deeper than the average depth of the Wabash above Mackey Island and deeper than the cut-off. The current speed was significantly less than in the cut-off. It averaged only 1.7 MPH. That is only about 1/3 of the speed of the new channel. Why are these factors important? Knowing this will help to determine how permanent this new island may be:
- Since the current is running so much faster into the cut-off, this channel is likely to continue to become deeper and wider.
- The average depth of the old channel is sufficient and will continue to be navigable for a long time. This means that this new island will likely remain as an island for many years before it silts up...or it may never close up!
- Most physical
changes will come during high water, however, since this is so close to
the Ohio River it will be influenced by the fact that during low water on
the Wabash River, this section will tend to become backwaters from the
Ohio and be stabilized to some extent. The Ohio River has dams and a certain "pool stage" is normally maintained. This factor and when the Ohio River
is running high will help maintain water in the old channel which is
another reason that the old channel may continue to have sufficient water.
- The slower current around the right side of Mackey Island could become subject to logjams and silt build-up. If this happens the river could eventually close up from the island to the Illinois shore and in the island chute, leaving the new channel as the only means to pass through the section of river by boat. This is a "could be" and if so, would take several years.
Is the Wabash River six miles shorter yet? No. Could it be someday? Yes. Keep in mind that all of the measurements of current speed and channel depth will vary as the river rises and falls. The nearest river stage station is at New Harmony, IN. On the day that I was at this location the river stage at New Harmony was 10.2 feet. Given this depth as a measuring standard, one can predict with some accuracy what the river depth will be in this section, using the depths that I indicated. What makes this area tricky to predict is the influence of the Ohio River. For the time being, if the Wabash River is very low, a swift current may not be flowing through the new channel, but it will continue to scour and become deeper with each high water.
The most significant thing about this event is that the Wabash River has created it's largest island of 1,700 acres. The downside is that the landowners have lost access to this land and can no longer farm it. The upside is that this could be that if left alone, this land will revert back to nature and become a wonderful place for plant and wildlife. The best case scenario would be for a large organization like the Nature Conservancy to buy the land and make it a nature preserve. They have done this on the Ohio River with great success. I hope others will support this notion and join me in helping to publicize an effort to make this little corner of Indiana a Green Spot.
Anyone with additional information or questions may feel free to contact me. Also any agencies who would like to get hi-res downloads of the photos may have them for no charge by contacting me.
JULY 25th UPDATEThere has been a great response to the suggestion that this new island should be protected and allowed to revert back to nature. This would be a long-term undertaking and I encourage anyone interested to join in and see if we can indeed make this a "Green Spot" in Southwestern Indiana. One of the first things to do would be to contact the property owners to see if they would entertain the idea of selling the land. If it is possible to offer the landowners a fair price for the island, I believe that everyone would win. The farmers would recoup their losses and Indiana would gain some natural habitat (rather than loose more each year as we have). Please write to firstname.lastname@example.org if you have any information that may be helful.
A Greener Indiana is a great website that is ideal as a place for those of us who have any comments or other information to share concerning this project. The web address is agreenerindiana.com. I have started a forum called "Project Green Spot" and encourage those of you who have written to me and anyone interested to join the forum and participate. Please check back on this site and A Greener Indiana for updates. Together we could turn what some people claim to be a disaster into a wonderful place of forest and wildlife.
I just spoke with Michael McGovern, Public Affairs Specialist with the USDA. He informed me that the new island is being included in a federal stimulus program to compensate farmers with flood damaged land. What does this mean? The landowners will be paid to no longer farm the land and it will be allowed to returned to a natural state by nature. The land will continue to be owned by the present landowners but there will be many restrictions on the land use including farming, tree harvesting and excavations. This will be a permanent easement that will stay with the land if it is sold.
I have assumed all along that since island access is difficult that it would no longer be used for agriculture and therefore have a natural restoration, however, my concern was that someday the old bend may fill in creating way to build a road to the land and resume farming it. The beauty of this program is that the restrictions will continue, even if that happens.
This is an example of something very good resulting from a flood. It also demonstrates the positive affect of collective efforts and the success of this web site. I was told that "agreenerindiana.com" and "indianawaterways.org" web sites were important tools for their research on this program.
I want to thank all of you for your support in this project. We will have our "Green Spot" in southwest Indiana. I'm not sure whether there is a need to continue this group but I will keep it up for a while, in case there are comments. Let's celebrate!
Update...June 18, 2009
Marc Hawley took the following photos of yet another cut formed at Mackey Bend this month. This one cuts across at a point upstream from the cut made last year. The first photo is taken looking toward the Wabash at the source of the cut. This means that there are now two Islands and Marc says that it appears that these new channels and the old bend are all stable and will likely continue to flow with no sign that they will close up in the near future. Not only that, there are additional cuts forming in the same area. The second photo was taken of a third cut forming that will likely find its way through during subsequent high water, forming yet a third island. Marc says that other cuts are forming. This could eventually mean that there will be a maze of islands in this section of the lower Wabash River. Fascinating stuff! I will return the this area by boat as soon as possible and also hopefully obtain some aerial photos. There is now well over 2,000 acres of land that has been cut-off by the river and formed new islands. Additional updates coming soon.