ACCURACY OF SAND VOLUMES AS A FUNCTION OF SURVEY DENSITY

Jennifer L. Irish, W. Jeff Lillycrop, Larry E. Parson

Abstract


Hydrographic surveys are the primary tool for calculating beach nourishment project volumes. With costs for beach-quality sand as high as $30 US per cubic meter, miscalculating project design volumes can result in significant cost differentials. Because conventional bathymetry and topography of beach projects are collected along shore-normal profile lines spaced anywhere from 30 m to 300 m, calculation of project volumes relies heavily on the assumption that there is little along-shore variability from one profile to another. In most cases, however, the beach and nearshore are highly irregular and this assumption is violated. With the development of high-resolution bathymeters, such as the SHOALS airborne lidar system, it is now feasible to collect accurate, high-density beach surveys. These types of data sets create a highly accurate, quantitative measurement of beach and nearshore conditions. This paper describes the SHOALS system and lidar technology and presents a comparison of volumes calculated using high-density lidar data and conventional nearshore profile surveys. Volumes are calculated to compare differences for beaches on the Atlantic Ocean, the Gulf of Mexico, and the Great Lakes.

Keywords


sand volumes; survey density

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