What is the wave steepness threshold at which waves tend to become unstable?

The wave steepness threshold at which waves tend to become unstable is defined by the ratio of wave height to wavelength. When this ratio exceeds approximately 1:7, the waves are considered to be steep enough that they may begin to break or no longer maintain their shape effectively. This instability leads to phenomena such as wave breaking, which can produce dangerous conditions for sailing, flying, and other activities near or on the water.

In the context of wave behavior, a steepness of greater than 1:7 means that the height of the wave exceeds 1/7th of its wavelength, indicating that the wave has excessive energy relative to its size, leading to potential instability. Recognizing this threshold is crucial for navigators and water sports enthusiasts, as it allows them to anticipate and avoid hazardous conditions that can arise from steep, unstable waves.