A significant rainfall event over the 4th of July weekend in the Wabash River Basin in Indiana caused a chain of events affecting the navigation channel in the Ohio River below J.T. Myers Locks and Dam. Runoff from the slow-moving storm eroded the Wabash River banks causing large sections to slough off, depositing whole trees and sediment at the mouth of the Wabash in the Ohio River.
River traffic was shut down as a result of debris, silt, sand, gravel and trees that closed the navigation channel to commercial traffic. Because the flow in the Ohio River was low and unable to carry the material downstream, a large sand bar of approximately 2 million cubic yards blocked the channel. The sand and debris field — roughly equivalent to seven football fields in size — created what would become a large exposed sand island at normal pool.
"It quickly becomes a navigation crisis because of the economic impacts that would affect the region if goods don’t get to their destinations in a timely manner," said Barry Vessels, dredge team leader.
With the dredge vessel upstream at Cannelton Locks and Dam, it was quickly diverted to the channel closure by Louisville District Operations. This was accomplished by a cooperative effort working with the Coast Guard, contractors and industry. First, buoys were placed to mark a temporary channel, and then the dredge was positioned to clear the blockage. The towing industry provided a helper boat to separate full tows into smaller units that negotiate the temporary channel. The Corps hydrographic survey team conducted several surveys to analyze the channel condition and produced graphics for the emergency conditions which would allow tow traffic to begin to move.
On July 6 the team was in action and had marked the temporary navigable channel. On July 7, the Coast Guard set approximately one half mile of buoys to help mark a new channel so tows could have a route to pass through the area. As the heavy flow from the Wabash River declined, the contract dredge, the Bill Holman, began dredging July 9. This was welcome information for the towing industry because by that time more than 20 tows were waiting to lock through at J.T. Myers just upstream.
According to Vessels and Todd Davis, Army Corps of Engineers dredge inspector, the amount of material deposited into the navigation created the worst blockage in recent record.
"The situation was unique," said Davis who oversees the dredging contractor. "When you see trees washing into the river and parts of the Indiana banks falling and caving in, that’s bad."
Vessels noted that a 2008 flood event set the stage for July’s material deposit in the channel. Previous events created a large region of conditions that were affected by the rise and fall of the river with each significant rainfall event. Riverbanks became weakened over time, and began to collapse which in turn created a shallower channel and a wider river due to sediment deposits. The increased flow in early July scoured out the shallower river. "We experience shoaling and run-out from the Wabash River, and we know that if the river shuts down in this area, the queue (line of waiting tows) builds very fast," said Quent Harris, port captain, AEP River Operations, Paducah, Ky.,
Fortunately, dredging can provide a relatively quick solution. First, the dredge cutter head stirs up the material which is then pumped through a pipeline that has been laid out to a designated disposal area. Environmental permits must be obtained from the state before dredging could begin to satisfy Indiana environmental requirements. Davis said the material is examined for special concern species such as threatened and endangered mussels. Any that turn up are identified.
The dredging operation continued well into August to ensure that the re-established channel would provide continued safe navigation. The dredge works 24/7 to minimize the disruption to the navigation industry. The Coast Guard and the Corps will continue to work together to identify a more long-term solution to channel management. "We are on call 24/7 to do what it takes to maintain navigation," said Vessels.