Duxbury Beach, Massachusetts, is a retreating, transgressive barrier that is effectively managed to meet a range of competing land uses. While the barrier is heralded as a natural coastal setting, the entire landform is methodically engineered on an ongoing basis to best accomplish the goals established for the beach within a context of natural processes. Historical and geological data indicate that the natural barrier form includes numerous ephemeral tidal inlets (some of which have migrated) and overwash channels, and low discontinuous dunes. At present, the managed barrier has a continuous vegetated foredune and broad backdune. Management techniques have evolved over the past several decades based on growing experience and understanding of the coastal processes and of wildlife habitats. Although the foredune crest is reconstructed each spring, the entire beach is gradually being allowed to retreat to remain in equilibrium with rising sea level. The lagoonal shore is being widened through beach nourishment and through proposed creation of back-barrier salt marshes using silty dredge spoil. Uses of the barrier include town and public recreational beaches, off-road vehicle access, a right-of-way to isolated communities, flood protection of landward areas, and shorebird nesting habitat.

Ground penetrating radar (GPR) records of groundwater surface (GWS) reflections have been analyzed from 40 across-barrier profiles, totaling 50 km in combined length, taken from barrier spits and beach plains of the Columbia River littoral system. The barriers and beach plains host shallow fresh-water aquifers in the prograded beach deposits and abandoned foredune ridges, totaling 10–30 m in thickness. Study results demonstrate that GWS reflections could be traced continuously at subsurface depths of 1–15 m with the GPR 100 MHz and 50 MHz antennae using 400 V and 1000 V transmitters. Boreholes (62 in number) and lake water levels (24 in number) provide ground-truthing of the across-barrier GWS trends interpreted from the GPR profiles. The GWS rises in elevation (4–8 m above base level) under high, broad foredune-ridges and drops under interdune ridge valleys (1–3 m above base level). Continuous profiles of GWS demonstrate that lakes, ponds, and bogs of the barriers and beach plains are “windows” into the shallow coastal aquifer. The GPR records demonstrate that the GWS slopes either to seaward (0.003–0.04 gradient) or to landward (0.001–0.05 gradient) from divides under the largest, shore-parallel dune ridges in the barriers. The GWS gradients indicate that subsurface contaminant transport from the developed dune ridges will be intercepted by intervening lakes and ponds in the interdune-ridge valleys. The GPR records also establish the effect of drainage ditches in lowering GWS elevations (1–2 m) in sensitive wetlands located 100s of meters in distance from the constructed ditches.

Abstract The Columbia River empties into the Pacific Ocean near latitude 46° N. Much of the detrital load of the river is distributed over a 165 km long littoral cell between Tillamook Head, Oregon, and Point Grenville, Washington. The cell is characterized by north-directed littoral drift in response to dominant southwest winter storms, yet it experiences a summer drift reversal in response to more modest northwest winds and seas. The result has been development of extensive barrier beaches during the late Holocene, which define the major embayments of Willapa Bay and Grays Harbor. The mouth of the Columbia River was modified by jetties beginning late in the nineteenth century. The entrance to Grays Harbor has been jettied since early in the twentieth century. This article discusses changes resulting from these modifications. Dams on the Columbia River and its tributaries built during the twentieth century appear to have significantly reduced the detrital load available to the littoral cell, resulting in the onset of changes in the deposition-erosion regimen.

In central and eastern Alabama, the 450-m-thick Upper Cretaceous (upper Santonian–uppermost Maastrichtian) section is composed of various paralic (barrier-shoreline) and hemipelagic (shelfal) facies associations. Based on outcrop and shallow-subsurface studies, the Upper Cretaceous section is divided into several stratigraphic break-bounded genetic packages of facies. The bounding stratigraphic breaks are either (1) low-relief surfaces characterized by thin conglomerates and facies discontinuities (probable parasequence boundaries or type-2 sequence boundaries), or (2) high-relief surfaces (probable type-1 sequence boundaries). The basal (upper Santonian–lower Campanian) Eutaw Formation, bounded at the top and base by type-2 and type-1 sequence boundaries, respectively, consists of paralic facies arranged in two genetic packages that are separated by a low-relief break (probable maximum-flooding parasequence boundary). The overlying (lower Campanian) Mooreville-Blufftown interval encompasses shelfal and paralic facies arranged in four genetic packages. Low-relief breaks within the Mooreville-Blufftown interval are probable parasequence boundaries; the break between the Mooreville-Blufftown and the overlying Demopolis-Cusseta interval is a probable type-1 sequence boundary (age of boundary is approximately 80 Ma). In the upper Campanian Demopolis-Cusseta interval, shelfal and paralic facies occur in three genetic packages, bounded by low-relief (type-2) stratigraphic breaks. A probable type-2 sequence boundary occurs between the Demopolis-Cusseta interval and the overlying Ripley Formation. The Ripley Formation (lower and upper Maastrichtian) is composed of paralic facies, encompasses one probable type-1 sequence boundary, and has a type-1 sequence boundary with 67 m of relief at its top (age of boundary top is approximately 68 Ma). The overlying Prairie-Bluff–Providence interval (uppermost Maastrichtian) encompasses shelfal and paralic facies arranged in two genetic packages. A probable parasequence boundary occurs within the Prairie Bluff–Providence interval and a type-1 sequence boundary with considerable relief occurs at the top of the interval. Review and analysis of study area biostratigraphy permits us to closely relate the genetic packages of facies and the stratigraphic breaks observed in this study to the current model of sequence stratigraphy that synthesizes previously documented global cycles of sea-level change in the Late Cretaceous.

The scientific origins of Gilbert’s geomorphic model are explored, and the distinctive character of that model is compared with that of the rival model of W. M. Davis, with special importance being given to the role of negative feedback by Gilbert. The early development of Gilbert’s ideas (1871, 1875a, 1876) are treated, culminating in a detailed analysis of his classic work on the Henry Mountains (1877). His later work on coastal geomorphology, notably with reference to Lake Bonneville (1881, 1890) and on glacial geomorphology, showed a continuing preoccupation with the relations between form and process. An analysis of geomorphic work since World War II highlights the overriding importance of Gilbert’s recent influence, particularly over the application of systems philosophy to the environmental sciences.