Presence of Beach-Compatible Sediments in Offshore Borrows: New Challenges and Trade Offs in Developing Codifications

Appropriate protocols are required for selection of beach-compatible sediments from offshore borrows. Determination of what constitutes ‘native' beach sand can be problematic where prior renourishment modifies true native beach sediments. Because borrow sands must at some level approximate ‘native beach sediments,' offshore exploration methodologies need to efficiently differentiate bottom sediments into usable and non-usable categories. Sand search models (SSMs) are one approach where exploration protocols are based on literature searches and geophysical-geotechnical techniques that are conditioned by regional geomorphology, sediment dynamics, sedimentary properties, seismostratigraphy (calibrated with vibracores), and deposit morphologies (including facies recognition). Engineering-environmental performance guides attempts to ‘match' borrow sediments with existing beach sands, but exact matches always may not be found in offshore materials. This guidance is, in large part, a balancing act that attempts to replicate beach stability and biological beach performance where trade offs are inevitable.