Depth of Disturbance

Definition

Depth of disturbance, is the depth to which wave action can be expected to disturb the underlying bottom sediment. Sources of disturbance other than wind waves are not discussed. The sediment is considered to be unconsolidated particles in the sand size range.

Background

The approach adopted is to develop analytic expressions to estimate the depth of disturbance through the use of the velocity ratio,

(Eq. 1)

where u _{−h max} is the maximum near-bottom orbital velocity of the wave and u _crit is the critical velocity required to initiate sediment movement under the wave. If U is greater than 1.0, then movement of the sediment would be expected; if U is less than 1.0, sediment movement would not be expected. Ahrens and Hands (1998) found the parameter U very effective for distinguishing between beach erosion/accretion events. For shallow water conditions, u _{−h max} will be estimated using Stream Function Wave Theory (SFWT), Dean (1974). For deep water, u _{-h max}will be estimated...