A sand beach
erosion amount predicting method comprises the following steps that firstly, the
breaking wave height Hb is calculated, Hb=0.39g<0.2>(TH0<2>)<0.4>, g is the
gravitational acceleration, H0 is the deepwater
wave height, T is the
wave period, T0 is the wave
duration time, and h is the sand beach water increasing depth; secondly, the
wave speed u0, shown in the specification, at the sand beach position is calculated; thirdly, the wave number Ni corresponding to different wave heights is calculated; fourthly, the
erosion shear stress caused to the beach face from the
waves is calculated, Tauw=0.5FwRhowu0<2>, in the formula, Fw is the
friction coefficient between
water flow and a soil body, and rhow is the
seawater density; fifthly, the sandy soil anti-
erosion critical
shear stress is calculated, tauc=2 / 3 ds (rhos-rhow) g tanphi, ds is the sandy soil median size, rhos is the sand
grain density, and phi is the
internal friction angle of sandy soil; and sixthly, the sand beach erosion amount shown in the specification is calculated, in the formula, Es is the wave erosion amount, Ni is the wave number corresponding to the ith
wave height, Ks and a are
conversion coefficients for converting the erosion force into the erosion amount, and a is 1.0. The method has the beneficial effects that steps are simple, and the result is reliable, and providing the theoretical guidance for sand beach disaster reduction and protection is the purpose.