Ap.pendiees
311
APPENDICES
1
Beach Profiles
Since 'beach profile nourishment" is nowadays the recommended approach, the
calculation of such profile takes on a special significance. Such profile must be
specified because mode of sediment transport differs in near- and off-shore zones.
Profile changes in offshore depth-zones are negligible over several decades, but
where depths do not reach 20 m (+ 70 ft) data must be of recent vintage. Longterm swell stability and short-term transposition from swell to storm beach profile
require calculation of beach profiles as well as their correlations with sediments
characteristics.
1.1
The offshore profile
Swell waves may, in the long term, be barred from reaching a part of a coast, by
creation of a coastal barrier. A new wave climate will ensue. Refraction and/or
diffraction may cause wave height decrease. Wave energy dissipated along a
longer beach will be concentrated on a shorter distance and the swell is faced
more directly. Conversely a beach section may be subjected to lesser waves.
Another scenario occurs with sedimentation when the deposition is hampered
where a river debouches, due to natural or anthropic actions e.g. barrage
construction upstream. Any change in beach nourishment may bring about a
modification in sediment size ; knowing the probable equilibrium profile would
help determining needed fill volume to attain stability.
It is therefore useful to attempt establishing a relationship between mean wave
conditions and mean sediment characteristics for a stable underwater profile,
theoretical or albeit empirical.
A steeper or flatter than so-called '~tandard" beach profile indicate respectively
erosion or accretion. Closely associated, in ocean margins, with sustained swell,
the wave climate is even more important in enclosed seas and gulfs as here storm
waves are the only energy source.
311
APPENDICES
1
Beach Profiles
Since 'beach profile nourishment" is nowadays the recommended approach, the
calculation of such profile takes on a special significance. Such profile must be
specified because mode of sediment transport differs in near- and off-shore zones.
Profile changes in offshore depth-zones are negligible over several decades, but
where depths do not reach 20 m (+ 70 ft) data must be of recent vintage. Longterm swell stability and short-term transposition from swell to storm beach profile
require calculation of beach profiles as well as their correlations with sediments
characteristics.
1.1
The offshore profile
Swell waves may, in the long term, be barred from reaching a part of a coast, by
creation of a coastal barrier. A new wave climate will ensue. Refraction and/or
diffraction may cause wave height decrease. Wave energy dissipated along a
longer beach will be concentrated on a shorter distance and the swell is faced
more directly. Conversely a beach section may be subjected to lesser waves.
Another scenario occurs with sedimentation when the deposition is hampered
where a river debouches, due to natural or anthropic actions e.g. barrage
construction upstream. Any change in beach nourishment may bring about a
modification in sediment size ; knowing the probable equilibrium profile would
help determining needed fill volume to attain stability.
It is therefore useful to attempt establishing a relationship between mean wave
conditions and mean sediment characteristics for a stable underwater profile,
theoretical or albeit empirical.
A steeper or flatter than so-called '~tandard" beach profile indicate respectively
erosion or accretion. Closely associated, in ocean margins, with sustained swell,
the wave climate is even more important in enclosed seas and gulfs as here storm
waves are the only energy source.