Impact of River Channelization on Seismic Risk: Shelby County, Tennessee

Abstract

The lower 35.4 km of the Wolf River, in the city of Memphis, Shelby County, Tennessee, was channelized in 1964 to reduce flooding. Detailed channel surveys conducted in 1959 and 1990 document river and floodplain changes 26 years after channelization. Channelization resulted in a straighter, steeper, deeper, wider, and smoother channel, thus causing an increase in channel velocity, cross-sectional area, and discharge capacity. Subsequent to channelization, Wolf River became shallower near its mouth, entrenched 3 m in its upstream reach, and formed a nick point at the eastern end of the channelized reach that migrated 11.3 km upstream. Tributaries to the channelized segment of the Wolf River have also entrenched. In addition, the floodplain along the channelized reach underwent dissection and denudation and the banks of the Wolf River were an average of 1 m lower in elevation than they were in 1959. Channelization and subsequent river changes have reduced flooding in the channelized portion of the river as intended. However, negative consequences of these river changes include (1) costly bridge and pipeline repair, (2) river and wetlands habitat destruction, (3) probable increased susceptibility for earthquake liquefaction and associated lateral spreading of the Wolf River floodplain, and (4) increased earthquake risk due to building development on the Wolf River floodplain.