At what wind speed do waves continue to grow at a decreasing rate?

Waves continue to grow at a decreasing rate when the wind speed reaches a certain threshold where the energy input from the wind is balanced by the energy dissipation due to wave breaking and other factors. This point typically corresponds to moderate to strong wind conditions.

In this context, the wind speed of approximately 48.67 kph (the chosen answer) is significant because it falls within the range where the momentum transfer from wind to water begins to decrease in effectiveness as the waves start to approach their maximum height for the given wind conditions. At this speed, wave growth will still occur, but it will happen at a slower rate as wind energy becomes increasingly redistributed and absorbed by the growing wave field.

Higher wind speeds, such as 100 kph or 146 kph, contribute to more turbulent conditions, causing waves to reach their maximum potential more rapidly. Conversely, a lower wind speed, like 30 kph, would not be sufficient to generate significant wave height, hence not leading to a scenario where wave growth starts to taper off.

Thus, the answer is appropriate because it represents the wind speed at which waves still grow but at a diminishing rate, balancing the dynamics of energy input and dissipation.