Contaminant and sediment transport by advection and diffusion 235
xlabel('Longitudinal distance x 20 [m]')
ylabel('Coastline profile [m]')
% subroutibe "hline";
h=hline(0,'b','Original coastline');
% subroutine "vline";
h=vline(x_groin,'m','Groin');
PROBLEM 8.7
Solve the same problem by making the suggested modifications while keeping the rest of the data constant:
1. Change the sediment transport coefficient from 0.02 to 0.1, 0.01,
0.001 and 0.0001.
2. Change the empirical exponent from 2.5 to 2.0, 3.0 and 3.5.
3. Change the wave height by a factor of 0.5, 1.5 and 2.0.
4. Change the wave breaking angle by a factor of 0.5, 1.2, 1.5 and 1.7.
5. Modify the code so that at the transport coefficient changes linearly
from 0.02 at the beginning of the simulation to 0.0002 at the end of
the simulation.
Conduct the simulations, compare and explain the results, and comment
on the observations regarding the development of the upstream aggradation and the downstream erosion of the coastline.
8.4.4 Cross-shore sediment transport by waves
8.4.4.1 Conceptual description
The development of alongshore sandbars is a very important physical process resulting from onshore–offshore sediment movement by waves in the
wave breaking zone. Alongshore sandbars can act as a natural coastal
defence against winter waves, that is, those with high steepness (H/L), and
consequently with the strongest erosive capacity. Qualitatively the process
can be described as follows:
1. In the zone offshore of the wave breaking line, the waves transport
sediment as bed load towards the coast, while in the mid-depth water
layer, sediments are transported offshore as suspended sediment.
2. Inside the breaker zone the waves take the form of a sequence of
quasi-solitary waves, transporting water masses towards the coast,
and resulting to a mean-water-surface setup, Δη, related to the wave
height and period.
3. The transported water masses return to the sea via a strong near-bed
current, the ‘undertow’, which also transports sediments as bed load
towards the open sea.
xlabel('Longitudinal distance x 20 [m]')
ylabel('Coastline profile [m]')
% subroutibe "hline";
h=hline(0,'b','Original coastline');
% subroutine "vline";
h=vline(x_groin,'m','Groin');
PROBLEM 8.7
Solve the same problem by making the suggested modifications while keeping the rest of the data constant:
1. Change the sediment transport coefficient from 0.02 to 0.1, 0.01,
0.001 and 0.0001.
2. Change the empirical exponent from 2.5 to 2.0, 3.0 and 3.5.
3. Change the wave height by a factor of 0.5, 1.5 and 2.0.
4. Change the wave breaking angle by a factor of 0.5, 1.2, 1.5 and 1.7.
5. Modify the code so that at the transport coefficient changes linearly
from 0.02 at the beginning of the simulation to 0.0002 at the end of
the simulation.
Conduct the simulations, compare and explain the results, and comment
on the observations regarding the development of the upstream aggradation and the downstream erosion of the coastline.
8.4.4 Cross-shore sediment transport by waves
8.4.4.1 Conceptual description
The development of alongshore sandbars is a very important physical process resulting from onshore–offshore sediment movement by waves in the
wave breaking zone. Alongshore sandbars can act as a natural coastal
defence against winter waves, that is, those with high steepness (H/L), and
consequently with the strongest erosive capacity. Qualitatively the process
can be described as follows:
1. In the zone offshore of the wave breaking line, the waves transport
sediment as bed load towards the coast, while in the mid-depth water
layer, sediments are transported offshore as suspended sediment.
2. Inside the breaker zone the waves take the form of a sequence of
quasi-solitary waves, transporting water masses towards the coast,
and resulting to a mean-water-surface setup, Δη, related to the wave
height and period.
3. The transported water masses return to the sea via a strong near-bed
current, the ‘undertow’, which also transports sediments as bed load
towards the open sea.