Technically, Davenport's temporary flood barrier failed because of a lack of friction, and the force of the Mississippi River overcame its weight. A new report says several other factors contributed to the breach on April 30th.
In May, the city asked the Corps of Engineers to investigate the cause of the failure. And the engineers have now presented their report to the Davenport City Council.
Michelle O'Neill reports.
Roger Perk is the Chief of Engineering and Construction for the Corps of Engineers Rock Island District.
He says the barrier began to fail when the bottom of a Hesco basket began to slide, due to pressure from the Mississippi River.
The floodwater was slightly higher than the top of the Hesco baskets sitting on River Drive near Pershing Avenue with sandbags on top.
Calculations in the report show the barrier should not have failed but it did.
Perk and the report say the real world factors that caused the failure include, the flood stage at the time, "under-seepage" throughout the lengthy flood, steady rainfall on the day of the breach which left "the barrier foundation pavement wet," and "the high center of gravity, worsened by the placement of sand bags on top of the baskets."
Brandon Wright, Assistant City Administrator, says Davenport will immediately incorporate the recommendations into its flood plan to beef up flood protection.
That includes attaching a second row of unfiled Hesco baskets at the beginning of the flood fight.
Then as necessary, the city will fill the second row with sand and add another layer on top of those two rows.
The goal is to create more friction by adding weight to the flood wall and building it higher when necessary.
In addition, Wright says Davenport's updated flood plan will also reflect changes in the use of plastic sheeting. Employees will make sure only 6-12 inches are tucked under the front or river side of the Hesco barrier. And they won't cover the other side to make it easier to monitor the temporary flood wall for leaks and seepage.
Another recommendation is for Davenport to develop an outreach plan to teach residents and business owners about flood risk and the limits of temporary flood protection.
And a final recommendation is for Davenport to ensure employees receive the training necessary to build, monitor, and re-inforce the Hesco flood barrier system.
The city has posted a video of the corps' presentation online, along with the report itself. They are also posted below.