Wave base
Encyclopedia
The wave base is the maximum depth at which a water wave's passage causes significant water motion. For water depths larger than the wave base, bottom sediments are no longer stirred by the wave motion above.
In deep water, the water particles are moved in a circular orbital motion when a wave passes. The radius
of the circle of motion for any given water molecule decreases exponentially with increasing depth. The wave base, which is the depth of influence of a water wave, is about half the wavelength
. At depths greater than half the wavelength, the water motion is less than 4% of its value at the water surface and may be neglected
.
There are typically two wave bases, the fair weather wave base (FWWB) and the storm wave base (SWB). The fair weather wave base refers to the depth beneath the waves under normal conditions and the portion of the seafloor that is agitated by this everyday wave action is known as the Upper shoreface
. The storm wave base refers to the depths beneath storm-driven waves and can be much deeper. The portion of the seafloor that is agitated by this everyday wave action is known as the Lower shoreface
.
For instance, in a pool of water 1 metre deep, a wave with a 2-metre wavelength would barely be moving the water at the bottom. In the same pool, a wave with a wavelength of 1 foot would not be able to cause water movement on the bottom.
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
of the circle of motion for any given water molecule decreases exponentially with increasing depth. The wave base, which is the depth of influence of a water wave, is about half the wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
. At depths greater than half the wavelength, the water motion is less than 4% of its value at the water surface and may be neglected
Negligible
Negligible refers to the quantities so small that they can be ignored when studying the larger effect. Although related to the more mathematical concepts of infinitesimal, the idea of negligibility is particularly useful in practical disciplines like physics, chemistry, mechanical and electronic...
.
There are typically two wave bases, the fair weather wave base (FWWB) and the storm wave base (SWB). The fair weather wave base refers to the depth beneath the waves under normal conditions and the portion of the seafloor that is agitated by this everyday wave action is known as the Upper shoreface
Upper shoreface
Upper Shoreface refers to the portion of the seafloor that is shallow enough to be agitated by everyday wave action . Below that is lower shoreface.-Overview:...
. The storm wave base refers to the depths beneath storm-driven waves and can be much deeper. The portion of the seafloor that is agitated by this everyday wave action is known as the Lower shoreface
Lower shoreface
Lower Shoreface refers to the portion of the seafloor or sedimentary depositional environment that lies below everyday wave base . In this portion of the coastal environment, only the larger waves produced during storms have the power to agitate the sea bottom...
.
For instance, in a pool of water 1 metre deep, a wave with a 2-metre wavelength would barely be moving the water at the bottom. In the same pool, a wave with a wavelength of 1 foot would not be able to cause water movement on the bottom.