Investigation of the mechanisms responsible for morphological change in the vicinity of submerged geotextiles for shore protection

This study presents the results of an experimental investigation of morphology change in the vicinity of submerged geotextiles placed within the surfzone. The study was motivated by the emerging use of submerged geotextile tubes for shore protection, shoreline stabilization, and surf amenity enhancement. A physical model was conducted at the US Army Engineer Research and Development Center Large-scale Sediment Transport Facility (LSTF) where three geotextile alternatives were tested. The second alternative test was used to compare the observed scour in the vicinity of the geotextiles to a previous study of scour in the vicinity of submerged cylinders. Formulations developed by Catano-Lopera and Garcia (2006) relating the Keulegan-Carpenter (KC), Shields (theta) and Reynolds (Re) numbers to the scour depth were used to predict the scour observed during the LSTF experiment. Results show that the formulations over predict the observed scour when calculated using the maximum KC, theta, and Re numbers. The difference between the predicted scour and observed scour can be related to the incident wave angle in the LSTF. New empirical estimations were developed to predict the mean scour depth under oblique wave breaking as a function of the maximum KC, theta, and Re numbers.