In 1860, residents living in Danbury, Connecticut banded together to build a large, earthen dam to create a reservoir that would provide a sufficient water supply for the town’s steadily increasing population and burgeoning factories. A few years later, they built a second dam about a mile downriver, and the structures became known as the Upper and Lower Kohanza Dams, named for the Kohanza Brook that flowed from the newly built reservoirs into the heart of downtown Danbury two miles away.

In late 1868, a slight crack was discovered in the Upper Kohanza Dam, but no action was taken. Residents were confident that such a small fault would have no effect on the massive earthwork. On the frigid evening of January 31, 1869, however, disaster struck as the upper dam collapsed under the pressure of the ice-choked body of water it was designed to hold back. As the wall of icy water roared downstream, it completely washed away the Lower Kohanza Dam. Minutes later, a massive wave containing two reservoirs’ worth of water, as well as ice chunks, boulders, and tree trunks, slammed into downtown Danbury. A February report in Harper’s Weekly described the terrible moment in sensational detail:

“With terrible velocity [the floodwaters] struck the houses on Main Street near the river bank, instantly sweeping them from their foundations. …The water seethed and roared fifteen feet above the bed of the river; the noise of wrecked houses mingled with the screams of drowning men, women, and children; and what the water did not overwhelm was demolished by the rushing ice and timber.”

At least 11 people were confirmed killed by the flash flood, which had come and gone in less than 30 minutes. Bridges, railroad tracks, and factory buildings were completely destroyed, ensuring a long and painful rebuilding process for the town. By all accounts, the flood caused by the broken Kohanza dams was the worst recorded disaster in Danbury’s long history, in terms of both lives lost and property destroyed. In spite of the disaster, the Kohanza dams were eventually rebuilt, though on a much smaller scale than before. A double dam disaster brought a half hour of hell to Danbury, today in Connecticut history.

An illustration of the aftermath of the Kohanza Dam disaster, from the February 20, 1869 issue of Harper’s Weekly.

Further Reading

“Frozen Reservoir Destroys Danbury,” connecticuthistory.org