Assessment of Scour Potential under Wave Action Using ISEEP

Field testing with ISEEP was conducted at Jennette’s Pier, located in Nags Head, NC. The Pier is subjected to high energy waves on a daily basis, and one of its piles was fitted with a Nortek acoustic beams device that monitors distance from the sensor to the seabed with time. An approach is introduced for assessing the wave-induced bed shear stress and stream power as a function of the wave parameters. The data from ISEEP are used along with the estimated stream power to assess the scour rate at one of the pier’s pile. The computed results are presented for wave heights of 1–5 m and wave periods that ranged from 8 to 17 s. ISEEP data indicted two subsurface sand layers with the lower layer having smaller detachment rate coefficient. This is confirmed by the fact that the lower layer has a coarser grain size distribution with shell fragments. Using an average wave period of 17 s and an average wave height of 3.5 m, results using the ISEEP data with the proposed approach illustrated the possibility of obtaining scour levels similar in magnitude to the monitored data. A direct comparison between measured and computed results with time was however not possible since the time resolution of the collected wave parameters was too coarse, and backfilling of the scour hole with loose sand occurred with time.