English: Shoaling coefficient K_S as a function of relative water depth h/L₀, describing the effect of wave shoaling on the wave height – based on conservation of energy and results from Airy wave theory. The local wave height H at a certain mean water depth h is equal to H = K_S H₀, with H₀ the wave height in deep water (i.e. when the water depth is greater than about half the wavelength). The shoaling coefficient K_S depends on h/L₀, where L₀ is the wavelength in deep water: L₀ = g/(2π) T², with T the wave period and g the gravity of Earth. The blue line is the shoaling coefficient according to Green's law for waves in shallow water, i.e. when the water depth is less than 1/20 times the local wavelength L = T √(gh).