Four-year performance and associated controlling factors of several beach nourishment projects along three adjacent barrier islands, west-central Florida, USA Tiffany M. Roberts ⁎, Ping Wang Department of Geology, University of South Florida, 4202 E. Fowler Ave., SCA 528, Tampa, FL 33620, USA abstract article info Article history: Received 3 April 2012 Received in revised form 5 June 2012 Accepted 6 June 2012 Available online 17 July 2012 Keywords: Beach nourishment Longshore sediment transport Cross-shore sediment transport Beach profiles Beach morphodynamics Barrier island beaches To quantify the performance of several beach nourishment projects on three adjacent barrier islands located in west-central Florida, a total of 5200 beach and nearshore-profiles spaced at 300 m were surveyed monthly to bi-monthly from 2006 to 2010. Beach nourishment performance at annual temporal and kilometer spatial scales within the microtidal low-wave energy barrier island coast is most significantly influenced by the in- terruption of longshore sediment transport by complex tidal-inlet processes. The inlet processes directly influencing adjacent beach nourishment performance include longshore transport interruption resulting from divergence induced by wave refraction over an ebb-tidal shoal, flood-tidal currents along the beach, and total littoral blockage by structured inlets. Secondary factors controlling the nourishment performance include project length and width, shoreline orientation, and antecedent geology. A morphologic indicator of a large longshore transport gradient within the study area is the absence of a nearshore sandbar. These non-barred beaches are characterized by persistent shoreline erosion. The presence of a sandbar indicates the dominance of cross-shore processes, with bar migration in response to wave condition variations and a relatively stable shoreline. The entirety of a barrier island system should be considered when evaluating the performance of a nourishment. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Especially common in Florida, beach nourishment is a widely implemented method for mitigating beach erosion (Davis et al., 2000). This ubiquitously used method is less intrusive as compared to hard structures and is typically less expensive, with the advantages of acting as a buffer to storms while also providing both a recreational beach and habitat for (often) endangered species (Hamm et al., 2002; Stauble and Kraus, 1993). Beach nourishment introduces a perturba- tion to the nearshore system subsequently modified by natural forces in both the cross-shore and longshore directions (Dean, 2002). How- ever, as coastal dynamics vary substantially along the world's evolv- ing coastlines, the specific cross- and longshore morphological changes vary with both space and time. Therefore, detailed physical monitoring of site-specific coastal processes and morphology follow- ing nourishments are essential to quantify and predict nourishment performance, gain a more complete understanding of the underlying causes of beach erosion, and improve project design (NRC, 1995). Important parameters in evaluating the efficacy of a nourishment often include (but are not limited to) the dry beach width, volume of sand remaining after a storm, and subaqueous sand volume deter- mining total volume remaining (NRC, 1995). Identification of appro- priate nourishment strategies in European countries are generally based on inherent beach properties such as volume, dry-beach width, and shoreline location (Hamm et al., 2002; Hanson et al., 2002). According to Browder and Dean (2000), project performance must be evaluated through adequate monitoring obtaining informa- tion on the volume of sand used for nourishment and the planform area remaining over the design-life of the project. In addition, time-dependent sediment transport gradients necessary to evaluate planform and profile evolution requires sufficiently detailed temporal and spatial resolution of the beach-profile changes following nourish- ments (Work and Dean, 1995). Controlling factors of nourishment performance vary among pro- jects, as well as over space and time. Benedet et al. (2007) evaluated a nourishment on Florida's east coast concluding that rather than wave transformation over bathymetric irregularities or alongshore grain-size distribution, the most significant factor influencing the de- velopment of erosional hotspots was the change in shoreline orienta- tion due to the nourishment itself, resulting in accelerated alongshore currents and increased sediment transport potential. Analyzing eight years of post-nourishment data from northwest Florida, Browder and Dean (2000) identified project performance as most significantly re- lated to the occurrence of storms and the proximity to tidal inlets. Capobianco et al. (2002) concluded that advancement of quality control and identification of uncertainty in modeling beach nourish- ments are of great significance for predicting project performance. Based on profile surveys extending to approximately -1.5 m water depth, Davis et al. (2000) identified several factors controlling a Coastal Engineering 70 (2012) 21–39 ⁎ Corresponding author. E-mail address: tmrober2@usf.edu (T.M. Roberts). 0378-3839/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.coastaleng.2012.06.003 Contents lists available at SciVerse ScienceDirect Coastal Engineering journal homepage: www.elsevier.com/locate/coastaleng