Why are the Bonneville Salt Flats so smooth?

The Bonneville Salt Flats are exceptionally smooth due to the regular flooding of their evaporative layers. As a playa, the site undergoes periodic inundation, a process that develops and maintains the near-perfect flatness characteristic of these arid-region landforms.12

When the flats are flooded, fine-grained sediments and salts concentrate in the water, which then slowly evaporates or infiltrates the ground. This cycle of flooding and evaporation ensures the surface remains level, eventually hardening to a concrete-like consistency by the end of the summer.231