Beach Fill Calculator
Using the equilibrium beach profile concept, the amount of required sand to build a beach with a given dry width is calculated. The required data are the original (native) and the fill sand grain sizes, the desired width of the fill beach, the berm height of the beach, and the depth of closure (the depth offshore beyond which the beach profile doesn't change). After you press the Calculate button, the figure shows the beach profile that results. The output includes the volume of sand required to create a beach fill of the specified width in cubic meters per meter of shoreline. (Multiply this number by the length of the fill project to obtain the total required volume.) The width of the picture is given by x_max (in meters).
The equilibrium beach profile is given by h = A x ^(2/3); that is, the depth is given by a profile parameter A (which depends on the grain size of the sand) times the distance offshore x raised to the 2/3 power. For the original beach, the profile parameter is A_N, and for the filled beach (denoted in the figure above by the magenta), the parameter is A_F.
With this applet, it is pretty easy to see that the coarser the fill material, the steeper the beach profile and the less sand is required to create a beach of a given width. Not that if the sand is too fine (compared with the native material), most of the sand will eventually be deposited offshore near the depth of closure.
Comments: Robert A. Dalrymple