ACCURACY OF SAND VOLUMES AS A FUNCTION OF SURVEY DENSITY

Resumen

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.