During the construction of the Missouri River navigation channel, the Army erected thousands of pile dikes and revetments to narrow, deepen, and straighten the wide, shallow, meandering stream. Once the engineering works went into the river, the Missouri deposited its heavy silt-load on the downstream side of the structures. Overtime, new, elevated lands appeared in the river’s floodplain. Side channels, marshlands, and scour holes – everything that constituted the floodplain – filled with alluvium. Accumulated sediments sharply reduced the floodplain’s ability to store floodwater. Valley farmers benefitted from the newly accreted land. They expanded their operations into the floodplain, planting row crops where native vegetation once grew. The floodplain’s loss meant the farmer’s monetary gain. Continue Reading »
From 1929 to 1940, the Great Plains experienced a devastating drought. Scorching temperatures, an over-abundance of sunshine, and dry winds ravaged the land. From the Dakotas to Texas, soils turned to powder and blew away. In those hard, lean years, plains residents experienced hundreds of deadly dust storms. The Black Blizzards threw billowing clouds of dirt into the atmosphere, blotted out the sun, suffocated stock animals, and inflicted a phenomenon known as dust pneumonia on the rural population. Untold numbers died from the respiratory ailment. Continue Reading »
Two days ago, the Iowa Department of Natural Resources reported that 950,000 trees along the Iowa side of the Missouri River are likely to die as a consequence of the Great Flood of 2011. How the Iowa DNR came up with that figure is anyone’s guess. I think the figure of 1 million trees would have been a more impressive number, or maybe 2 million. The reality is that no one knows how many trees are going to die in the months and years ahead. But it is apparent that astronomical numbers of trees will die. Continue Reading »
The Great Flood of 2011 altered the Missouri’s channel morphology in noticeable ways. In the unchannelized river at the foot of Ponca State Park (Ponca, Nebraska) the flood has rearranged the riverbed. Where fast, deep water once pushed heavily downstream, there is now a football-field-sized sandbar. Next to it, a dark, muddy shoal is beginning to emerge from the depths. Just upstream, the river is now careening through a once-calm side channel. Northwest of the bridge linking Newcastle, Nebraska, with Vermillion, South Dakota, numerous sandbars are visible in mid-channel. After a summer adrift on the waves, the topsoil of the Dakotas has finally found a resting place here. Continue Reading »
The Army’s navigation channel through the Sioux City metropolitan area appears to have survived the Great Flood of 2011 with only minimal damage. Even though powerful currents pushed rocks off riprapped wing dams and knocked askew the wooden poles atop pile dikes, the dikes and revetments continue to hold their positions in the river. The Mighty Missouri did not completely grind them down and carry them away. Rather, the training structures are at this moment directing the Missouri’s flow through what the Army calls the “design channel.” Continue Reading »
Sioux City, Iowa. The persistent high water of the Missouri is beginning to take a toll on the trees lining the stream’s banks. The saturated soil around the roots of the trees no longer provides a strong base of support. Thus, when high winds or strong river currents strike the vulnerable trees, they easily tumble over into the floodwater. Dozens of large and small trees are lying on their sides in the engorged Missouri just a mile downstream from its juncture with the Big Sioux River at Sioux City, Iowa. The number of downed trees is going to increase exponentially as the summer moves toward fall and the Army keeps the discharge rate out of Gavin’s Point Dam at 160,000 cubic feet per second. The loss of bankline timber will increase runoff into the Missouri for years to come. Healthy timber tracts halt or slow runoff by storing water in root systems, trunks, and leaves. Once the trees are dead and gone, rain will hit the valley floor and more quickly drain into the Missouri. River edge trees also act as a natural means of bank stabilization. Trees slow down erosive currents, deflect water from the bankline, and keep valley soils from rapidly washing away. The absence of trees along the river will lead to intensified bank erosion. Additionally, the loss of timber strips adjacent to the river means that agricultural chemicals, feedlot fecal matter, and urban storm water (which contains automobile lubricants) will readily find its way to the Missouri. The destruction of river side timber will have serious negative repercussions for the health of the Missouri River ecosystem.