4. Coastal Erosion and Protection Measures Including Case Studies
103
properly are most likely to yield désirable results in a shorter duration of
time. However, improper designed and unskilled execution might end up
worsening the issue in hand.
4.5.2.1 Hard structures
Hard structures are solid and sturdy structures usually made up materials like rocks/rubble and concrète. Most of the Coastal protection schemes
involve construction of such hard structures. The various hard structures
in practice are discussed in detail below.
Offshore breakwaters
The main purposes of breakwaters are for the formation of artificial harbors, to protect an area inside the sea against waves, to reduce dredging
at harbor entrance, to serve as quay facility, to guide currents, to provide tranquility conditions inside the harbor. Offshore detached breakwaters are a widely adopted option for protecting the coast against érosion
along a littoral drift dominated coast and they hâve proven to be effective
in reducing and absorbing the incident wave energy. The waves around such
structures undergo transformations like, shoaling, refraction, diffraction
reflection from structures as well as the combined effects of ail these phenomena. Their cross-section is usually of mound type and are aligned parallel to the shore. These structures protect the shore by preventing the
direct attack of destructive waves. The advancement of the shoreline until
it reaches the breakwater is termed as “Salient” and when it reaches the
breakwater; it is termed as “tombolo”.
As the construction of offshore breakwaters requires skilled labor and
heavier machineries and quite expensive compared to shore connected structures, it should be considered only after ascertaining its effect as an effective protection through detailed investigations before implémentation. The
shoreline variation due to construction of a single offshore breakwater and
due to segmented offshore breakwaters is shown in Figs. 4.5(a) and 4.5(b),
respectively. Usually, the offshore breakwaters are of exposed type, and of
late, submerged type termed as multipurpose artificial reefs hâve become
popular.
Hanson and Kraus [1990] indicated that in general there are at least
fourteen parameters, including breakwater parameters, hydraulic conditions, and sédiment properties which control the shoreline response of a
sandy beach: The breakwater parameters are length of structure (LB);
103
properly are most likely to yield désirable results in a shorter duration of
time. However, improper designed and unskilled execution might end up
worsening the issue in hand.
4.5.2.1 Hard structures
Hard structures are solid and sturdy structures usually made up materials like rocks/rubble and concrète. Most of the Coastal protection schemes
involve construction of such hard structures. The various hard structures
in practice are discussed in detail below.
Offshore breakwaters
The main purposes of breakwaters are for the formation of artificial harbors, to protect an area inside the sea against waves, to reduce dredging
at harbor entrance, to serve as quay facility, to guide currents, to provide tranquility conditions inside the harbor. Offshore detached breakwaters are a widely adopted option for protecting the coast against érosion
along a littoral drift dominated coast and they hâve proven to be effective
in reducing and absorbing the incident wave energy. The waves around such
structures undergo transformations like, shoaling, refraction, diffraction
reflection from structures as well as the combined effects of ail these phenomena. Their cross-section is usually of mound type and are aligned parallel to the shore. These structures protect the shore by preventing the
direct attack of destructive waves. The advancement of the shoreline until
it reaches the breakwater is termed as “Salient” and when it reaches the
breakwater; it is termed as “tombolo”.
As the construction of offshore breakwaters requires skilled labor and
heavier machineries and quite expensive compared to shore connected structures, it should be considered only after ascertaining its effect as an effective protection through detailed investigations before implémentation. The
shoreline variation due to construction of a single offshore breakwater and
due to segmented offshore breakwaters is shown in Figs. 4.5(a) and 4.5(b),
respectively. Usually, the offshore breakwaters are of exposed type, and of
late, submerged type termed as multipurpose artificial reefs hâve become
popular.
Hanson and Kraus [1990] indicated that in general there are at least
fourteen parameters, including breakwater parameters, hydraulic conditions, and sédiment properties which control the shoreline response of a
sandy beach: The breakwater parameters are length of structure (LB);