How October, 1990 Storms Affected South Carolina Dams

Abstract Only - The ten-day period that began on October 10, 1990, is one that employees of the South Carolina Dam Program will long remember. During that time, tropical storm Klaus entered the state from the Atlantic coast and tropical storm Marcos affected the state from its western border. In the 16 counties that were worst affected, rainfall greatly exceeded the 100-year storm event in many locations. As a result of the heavy rainfall and resulting runoff, many dams were overtopped and a number of dams failed. To try to get control of the situation, employees of the Dam Safety Program (augmented by 3 engineers on loan form the U.S. Army Corps of Engineers and 2 engineers from the North Carolina Dam Safety Program) physically checked over 900 regulated dams in the affected counties. Seventeen dams were found to have failed, 81 showed evidence of overtopping, and 35 were classified as unsafe. The 6-month period that followed these events was one of the busiest since the passage of the Dam Safety Act in 1977. A large number of repair permits had to be processed, and the owners of unsafe dams had to be persuaded to take necessary action. Legal action had to be brought against two owners, and this resulted in one dam being repaired and a second one being breached. Lawsuits to settle some of the other issues encountered are still pending.