Abstract Coastal erosion impact on low-lying sandy shorelines represents a worldwide problem, which is particularly felt in various segments of the Portuguese coast where this geomorphological type represents 42% of its total length. Beach nourishment is a viable engineering alternative for shore protection and the assessment of offshore sources of beach-fill material is an essential aspect when implementing this mitigation strategy. The CHIMERA project carried out a multidisciplinary inspection on four segments of the west Portuguese coast to assess their potential as offshore borrow areas for beach nourishment. Altogether, these segments covered an area of c . 35 km 2 , at water depths between 20 and 42 m. They were surveyed using multibeam, sub-bottom profiler, ultra-high resolution multichannel seismics and a set of 126 surface samples and 72 vibrocores (with 3 m long each). To comply with the Portuguese legislation, sand types were assessed by granulometric and chemical analyses for evaluating the quality of sediments in terms of contamination. High-resolution magnetic surveys were conducted to find potential archaeological artefacts. The adopted methodology proved to be adequate to quantify and describe the spatial distribution of useful sediment volumes, supporting the ongoing Integrated Coastal Sediment Strategy for mainland Portugal.

Westhampton Beach is located between two stabilized inlets (Shinnecock and Moriches Inlets) on a barrier island on the south shore of Long Island, New York. Increasing beach erosion in the 1970s prompted a request for construction of a groin field to trap sand and restore the beach. The U.S. Army Corps of Engineers developed a plan for the groin field, and their recommendation was to sequentially build the groins up drift (eastward toward Shinnecock Inlet) using standard project design. However, in the late 1970s, local community pressure forced the U.S. Army Corps of Engineers, contrary to project design, to construct the groins down drift (westward) toward Moriches Inlet. The aim was to restore the eastern, more commercial, part of Westhampton Beach first. Financial limitations in 1972 suspended the project before its completion. Unfortunately, this set the stage for serious problems because the groin field was meant to operate as a completed project, and major problems developed soon after project termination. As a result, severe erosion and multiple washovers occurred west of the last groin. The major nor'easter of 1992 breached the island and destroyed many homes. The U.S. Army Corps of Engineers, in an emergency operation, dredged offshore sand and filled the breaches before they widened too much for effective closure. The subsequent litigation among the homeowners, the county, and the state spread over a number of years. A final settlement was reached on 31 October 1994. However, in a time of sea-level rise on a developed barrier island between two stabilized inlets, more people and bigger structures have now been put in peril.

Pea Island, Oregon Inlet, and Bodie Island, North Carolina, are severely human-modified barrier-island segments that are central to an age-old controversy pitting natural barrier-island dynamics against the economic development of coastal North Carolina. Bodie Island extends for 15 km from the Nags Head–Kitty Hawk urban area to the north shore of Oregon Inlet and is part of Cape Hatteras National Seashore. Pea Island extends 19.3 km from the southern shore of Oregon Inlet to Rodanthe Village and is the Pea Island National Wildlife Refuge. Bodie and Pea Islands evolved as classic inlet- and overwash-dominated (transgressive) simple barrier islands that are now separated by Oregon Inlet. The inlet was opened in 1846 by a hurricane and subsequently migrated 3.95 km past its present location by 1989. With construction of coastal Highway 12 on Bodie and Pea Islands (1952) and the Oregon Inlet bridge (1962–1963), this coastal segment has become a critical link for the Outer Banks economy and eight beach communities that occur from Rodanthe to Ocracoke. The ongoing natural processes have escalated efforts to stabilize these dynamic islands and associated inlet in time and space by utilizing massive rock jetties and revetments, kilometers of sand bags and constructed dune ridges, and extensive beach nourishment projects. As the coastal system responds to ongoing processes of rising sea level and storm dynamics, efforts to engineer fixes are increasing and now constitute a “human hurricane” that pits conventional utilization of the barriers against the natural coastal system dynamics that maintain barrier-island integrity over the long term.

As a result of the natural setting plus poor development and management decisions, the town of North Topsail Beach on Topsail Island, North Carolina, is the state's most vulnerable barrier-island community. It is our view that this very narrow, low, and duneless island community is the most hazardous on the U.S. East Coast. Although most of North Topsail Beach was designated a CoBRA unit under the Coastal Barrier Resources Act of 1982, the area has been developed extensively (mostly post-1980), starting with “mom and pop” beach cottages, and evolving into large single-family rental houses, duplexes, and several medium- and high-rise hotels and condos. Over the years, North Topsail Beach has experienced property losses from storm surge, overwash, flooding, inlet migration, new inlet formation, and chronic shoreline erosion. The single evacuation road crosses seven swash channels and is flooded early in every significant storm. A political cauldron has evolved, often featuring the front-row property owners versus those behind the front row, in which this middle-class town seeks to solve its problems. Debate centers on beach erosion problems, including proposed beach nourishment; exemptions to banned shore hardening; and construction of a proposed terminal groin and inlet channel realignment.

Folly Beach is a case study on the effects of multiple coastal barrier island management techniques. After the emplacement of the Charleston Harbor jetties in the late 1890s altered coastal sediment supply, Folly Island's beaches have retreated, and beachfront homeowners of the 1900s have attempted to slow the beach's retreat to protect their property along an eroding coast. The jetties interfere with the longshore transport of sand, depriving the beach of sand resources that has led to an erosion rate estimated between 0.3 m/yr and 1.8 m/yr. The town of Folly Beach has armored the shoreline and hard stabilization structures to protect property and prevent structures from being overwashed by waves. Now, property owners must rely on beach renourishment to retain a recreational beach and to protect their property. Charleston's wetlands, estuaries, and barrier islands are a major economic engine for the region, and Folly Beach is an important tourist destination. Politics, multiple measurement techniques, and poor understanding of the effects of hard stabilization structures on the beach have complicated the ability of policy makers and the public to navigate the variety of issues associated with coastal erosion in this region. Furthermore, its long history of development and attempts to stabilize the beach qualify Folly Island as one of America's most vulnerable beaches and an excellent case study on the effectiveness of different techniques in this dynamic system.

Southeast Florida's beaches, which are heavily developed and imperiled by rising sea level, continue to be seriously mismanaged and uneconomically maintained and to generate increasing environmental stress for adjacent marine habitats. Broward County heads the list of counties that stretch from St. Lucie southward to Miami-Dade. Five serious problems plague the stability of these barrier-island shorelines: inlet disruption of littoral drift; beach management that enhances shore erosion (lack of shore vegetation, inappropriate vehicular traffic, and structural protections that enhance erosion); historically very poor-quality renourishment sediment (in size and durability); strong resistance by coastal engineering and dredging firms and counties to embrace an understanding of sandy shore dynamics; and a philosophy that renourishment projects are a solve-all management approach to maintaining beaches and protecting infrastructure. This has led to seriously destabilized beaches, overly aggressive beachfront development, major economic waste, and severe environmental degradation to adjacent marine waters and associated valuable sandy bottom and hard-bottom communities. Many of these sandy shorelines may well not survive this global warming century of rapidly rising sea level. It is economically and environmentally critical for both the future risks to be understood and for lessons from the repeated failed history of beach management to be learned. Continued mismanagement will shorten the inhabitable lifetime of this developed sandy coast by decades and at great economic and environmental cost.

Galveston Island and Bolivar Peninsula have experienced a well-documented history of shoreline and bay shoreline change ranging from +3.63 m/yr to −1.95 m/yr. By integrating core, Light detection and ranging (LIDAR), and coastal change data, we develop a sand budget that attempts to quantify long-term sand sources (e.g., fluvial sand cannibalization through transgression) and sinks (washover fans, offshore sand bodies, and flood-tidal deltas). These results are then considered in light of anthropogenic influences (e.g., beach-nourishment projects, coastal engineering structures, and dredging operations) in an attempt to relate natural versus human influence on coastal change. Our findings suggest that hurricane washover (Galveston Island = 0.4 m/100 yr; Bolivar Peninsula varies from 0.154 m/100 yr to 0.095 m/100 yr) and offshore sand deposits are minimal long-term sand sinks. Flood-tidal deltas, however, appear to be major locations for natural sand sequestration. We also conclude that damming of rivers has had minimal impact on the upper Texas coast, although hard structures, such as the Galveston seawall and its groins, have exacerbated erosion along a shoreline that is currently sand starved. The impact of hard structures has mainly been one of trapping sand in locations where that sand would not have naturally accreted. Sand supply is minimal, so understanding and developing a better sand budget for the Texas coast are vital to sustainability.