If anyone needs proof that the Army’s navigation channel has reduced the conveyance capacity of the Missouri, they need look no further than the Army’s own satellite images posted at http://www.nwo.usace.army.mil/html/op-e/maps.html. The images of the unchannelized reach from Gavin’s Point Dam to Ponca, Nebraska, show the Missouri remaining almost entirely within its banks with a discharge rate of 150,000 cubic per second, which is the amount of water scheduled to be released from Gavin’s Point Dam by mid-June.
At Ponca, Nebraska, the Army’s channelization structures begin to hem in the river. Not coincidentally, it’s at Ponca that the Missouri is first shown pushing its floodwaters far out into the adjacent valley lowlands.
As the Missouri approaches Sioux City, the Army’s pile dikes and revetments squeeze the Missouri into a narrower channel than that which exists at Ponca. Here, the Missouri, at a discharge rate of 150,000 cubic feet per second, is shown inundating the lowlands even further afield.
With its satellite images, the Army has provided proof that the navigation channel lacks the conveyance capacity to safely carry the Missouri’s high flows. Thus, the Army’s pile dikes and revetments are a major contributing factor in the Great Missouri River Flood of 2011.