Flood Hazard Perception and Adjustment in Rapid City, South Dakota

Abstract

Through a series of circumstances, natural and manmade, an event of tragic proportions occurred in western South Dakota on June 9, 1972. A nearly stationary series of thunderstorms developed over the eastern Black Hills, producing as much as fifteen inches of rainfall in some locations and an overall average of six inches in the Rapid Creek drainage basin, upstream from Rapid City. It resulted in a flood which, according to the United States Geological Survey, produced the highest flood peak ever recorded in South Dakota. Although this flood exceeded the precious record peaks for selected sites in the Rapid City area, floods of greater relative magnitude have occurred in other areas of the United States. In the hours following the flood, the city was declared a disaster area and the Office of Emergency Preparedness of the United States Government moved to aid victims and to begin the task of rebuilding Rapid City. Prior to the 1972 flood, studies had been conducted by the United States Army Corp of Engineers in the Cheyenne River Basin of Western South Dakota. The studies concluded that acquisition and clearance of the floodway along the Rapid Creek tributary was not practical in light of the Corps’ cost-benefit analysis. In the aftermath of the catastrophe, the need to establish long-term contingencies for flood control in the heavily populated Rapid Creek floodplain became evident. The Urban Renewal Program under the auspices of the Department of Housing and Urban Development was selected to provide aid in funding a new floodway design by officials of Rapid City and the state of South Dakota. In the process of analyzing the Rapid City floodplain and the attitudes of those individuals living thereon, physical factors such as terrain, soils and vegetation and the meteorological setting must be first examined. Such information will provide a more meaningful background to the natural causes of flooding in the rapid City area