Abstract

The eastern shore of Great Salt Lake extends for 60 miles along the Wasatch Front. In historical time the static level of the lake has fluctuated 19 feet alternately flooding and exposing about 750 square miles of the lake bed adjacent to Wasatch Front communities. Historical data, geomorphic evidence, and theoretical calculations provide data on the frequency and magnitude of lake level fluctuations and associated flooding, which engineering geologists and others can use to guide land-use planning and development near the lake.

Twice in historical time Great Salt Lake has risen to an elevation of 4,212 feet above sea level. The second rise occurred in the 1980s and cost industry and government over $300 million. Rises to even higher levels should be considered in the design of structures on the lake bed. Wind setup and wave runup associated with sustained high-velocity winds cause flooding up to several feet above the static lake level. This super-elevation of the flooding level varies by several feet around the lake shore. The magnitude of the setup and runup is determined by wind velocity, fetch, lake depth, shoreline exposure, lake bed slope, and the configuration of the beach or constructed shoreline feature such as a dike or causeway.

Fluctuations in the level of Great Salt Lake correlate directly with variations in the amount of precipitation across the lake’s drainage basin. The lake level responds to wet and dry cycles several months or years in duration. Evaporation from the lake surface controls water loss from the lake. Human impacts such as structures that restrict circulation, diking for salt extraction, pumping to the West Desert, and consumptive use of water impact lake level and salinity.

Damage from rising waters of Great Salt Lake results from: 1- inundation, 2- wave action, 3-alteration of surface-water drainage, 4- rises of ground-water, 5- impacts on foundation stability, and 6-changes in salinity. Earthquake generated surges and dike failures pose flooding hazards for some areas of the lake bed. Proposals to build dikes on the bed of Great Salt Lake to provide permanent control of the lake level for selected stretches of the shoreline could transform the nature of the lake’s flooding hazard from gradual and non-life-threatening to sudden and life-threatening. Damage caused by the lake in response to a major earthquake or dike failure is likely to be exacerbated by high lake levels.