نبذة مختصرة : An active sand volume concept is introduced for the first time in this study. The significance of this new concept and its possible practical uses for Coastal Engineering are discussed. A theory is proposed towards quantification of the active sand volume across a beach profile and the circumstances under which it should be defined are determined. Next, a 12-year nearshore bathymetric data set surveyed at the Field Research Facility of the Army Corps of Engineers at Duck, NC is used to determine the hypothetical quantity of active volume. Statistical analysis of elevations at digitized cross-shore distances is performed and a site specific hypothetical active sand volume for the FRF is proposed as 630 m3 /m. The same data set is used to determine the actual quantity of active sand volume by means of volume analysis programs. The active volume concept is first subdivided into two as time-interval and event-dependent active sand volumes. The actual quantification is performed to cover long-term, fair-weather and storm periods, separately. Quantitatively, none of the active sand volumes under those categories converge to the hypothetical volume proposed. The maximum is about 185 m3 /m while the hypothetical volume is about 630 m3 /m. An empirical relationship between active sand volume and storm intensity is also established. Finally, it is concluded that the hypothesis about the theoretical quantity is not valid but the concept of active volume is important and can be widely used in hard and soft solutions to coastal problems such as in beach nourishment projects and assessing the effects of seawalls.
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