1999 Fort Calhoun Ravine Development

On the 6th and 7th of August 10 inches of rain fell. 12 inches in 24 hours is thought to be a 100 year event. This unusual precipitation event resulted in flooded cellars, sewage backups into cellars, local flooding, and local accelerated erosion within Omaha. These photos are from an area adjacent to a quarry a few miles north of Ft. Calhoun, a town some 17 miles North of Omaha, where a large ravine developed during the rain storm. A key player here was the quarry, which must have captured some of the water flow early in the storm. A positive feedback cycle occurred where as the ravine grew, it capture more of the rainwater increasing its erosive power into the soft flood plain sediments, causing it to grow faster. A road, fence and culvert were destroyed. The damage within and expense to the quarry is unknown, but is likely significant. The erosion closer to the main road (HW 75) had been filled with limestone quarry stone within two weeks. While the quarry produced an unusual set of conditions, this event also reminds us that large, but infrequent events may play a major role in shaping the landscape.

View of ravine with culvert pipe within it. Dark layer above is flood plain topsoil, and below are Missouri River alluvial sands.

Side gully that formed parallel to and then cut across a local road.

Looking down the axis of the main ravine and into the NE corner of the quarry the ravine emptied into.

View across farmer's field to the quarry workings. Again note the well developed layer of top soil and the channel sandstones beneath (with good cross beds).

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