Global sea-level rise increased during the twentieth century from 1.5 to 3.0 mm/yr and is expected to at least double over the next few decades. The Western Louisiana and Texas coast is especially vulnerable to sea-level rise due to low gradients, high subsidence, and depleted sediment supply. This Memoir describes the regional response of coastal environments to variable rates of sea-level rise and sediment supply during Holocene to modern time. It is based on results from more than six decades of research focused on coastal and nearshore stratigraphic records. The results are a wake-up call for those who underestimate the potential magnitude of coastal change over decadal to centennial time scales, with dramatic changes caused by accelerated sea-level rise and diminished sediment supply.

Abstract Central America is a small and culturally homogeneous region that, since the 1990s, has experienced economic and political integration of its six countries, which share the same threats of volcanic eruptions, disastrous earthquakes and tsunamis. The Pacific coastline of 1700 km is common for Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica and Panama, and the Pacific subduction zone has the potential for creating huge tsunamis that threaten this coast. In addition to the natural hazard, the growing tourist industry is expanding its infrastructure along the Pacific beaches, which again enhances the exposure and tsunami risk. Even though the 1992 tsunami disaster in Nicaragua did not severely hit the tourist beaches, it raised the risk awareness, and special attention is now given to ‘slow’ earthquakes that may be modest in shaking while still having a large tsunami potential. The tsunami hazard mapping is well advanced in Nicaragua, Costa Rica and El Salvador, and initiatives are ongoing to improve the mapping in all countries. National systems for early warning were established in Nicaragua and El Salvador, while the other four countries rely on rapid information from the Pacific Tsunami Warning Center. Mitigation measures and information campaigns are presently conducted on a national basis in all countries, but a regional centre for early tsunami warning and coordinated information campaigns (CATAC) is expected to become operational in the near future.

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.

A systematic pattern of beach ridges forming strandplains commonly fills embayments in the Great Lakes of North America. Ground penetrating radar (GPR) and vibracore results define a common preserved architecture inside beach ridges. Comparing the preserved architecture with a conceptual model of beach-ridge development explains the conditions responsible for their development and preservation. Great Lakes beach ridges are a product of a positive rate of sediment supply and a multidecadal fluctuation in lake level. Many shoreline behaviors occur throughout the development of a beach ridge, but not all successions originally formed by these behaviors are preserved. Beach ridges are stratigraphically separated by concave lakeward-dipping ravinement surfaces extending at depth below beach-ridge crests to the ground surface in adjacent landward swales. These surfaces are formed during rapid rises in water level, where previously laid deposits erode, forming a base for the beach-ridge core. As the rate of rise decreases and the water-level elevation approaches a highstand, the core of the ridge is built by vertical aggradation. Subsequent deposits build lakeward during progradation when water levels become stable, protecting the core from being eroded during future rapid rises in water level. Dune sand deposits on beach-ridge cores are stabilized by vegetation, and swales are commonly filled with organic material.

The Pearl River Delta with its network system and estuarine bays is unique and one of the most complicated large-scale estuarine systems in China. In this paper, a long-term morphodynamic model is developed to simulate the long-term morphological evolution of the Pearl River Delta. The concepts of long-term model calibration and verification are discussed. The paleo–estuary bay topography formed in the last interglacial period is reconstructed and serves as an initial and boundary condition of this model with time steps of 100 yr. Events of shorter duration are ignored. The driving forces and control factors considered in the long-term delta evolution include representative tides, sediment supply from the Pearl River system, sea-level variation, sediment condensation rates, and neotectonic movement. Deposition rates and total deposition volume are investigated and determined and then used to calibrate the model. Core data with 14 C dating at 30 locations are used to verify the model output with satisfactory results. Approximately 1700 collected cores are carefully analyzed to justify the model-simulated evolution processes. Morphodynamic analysis is conducted to justify and explain the output of the model on delta evolution and deposition modes. The study also provides more temporal and spatial details to the delta development originated from the effects of the morphodynamic structures, such as bidirectional jets and the “men” system. The model confirms that the complicated morphology, e.g., the rocky islands in the shallow estuarine bays, is one of the important factors affecting the long-term evolution of the Pearl River Delta.