Contaminant and sediment transport by advection and diffusion 233
The beach was discretized into 50 segments of Δx = 20 m each and the
time step used was Δt = 360 s. The deformation of the beach after a
period of 30 days is shown in Figure 8.10. The resulted profile is very
typical with those found in beaches where sediment deposits (accretion) in the direction of incoming waves and erodes (scouring) in the
leeway of the groin (or jetty).
Computer code 8.7
% Example 8.7 Coastal Evolution Subject to Longshore
Sediment Transport
% H = Reference water depth [m];
% at = Sediment transport coefficient;
% m = Empirical exponent [2 < m < 3.5];
% kk = Wave height magnitude modification coefficient;
% mm = Wave breaking angle magnitude modification
coefficient;
% Dx = Spatial step [m];
% Dt = Time step [s];
% nx = Number of spatial steps;
% nt = Number of time steps;
clc; clear all; close all;
% Input data;
H=2.5;
at=0.02;
m=2.5;
80
60
40
20
–20
–40
–60
0
0
5
10
15
20
25
30
35
40
45
50
Longitudinal distance × 20 (m)
Coastline profile (m)
Upstream
Downstream
Original coastline
Groin
Figure 8.10 Deformation of a beach profile around a groin.