Finkl, Charles W.

Many different kinds of classification have been applied to coasts in attempts to characterize dominant features in terms of physical or biological properties, modes of evolution, or geographic occurrence. Some of the earlier general classifications were broad in scope but lacked specificity while other specialized systems were narrowly focused, providing uneven coverage of taxonomic units for coastlines of the world. Due to more comprehensive study of coasts and the increasing availability of information, especially digital formats in GIS frameworks, integrated and systematic approaches to coastal classification are favored. The complex demands of today require sophisticated solutions to overlapping and interrelated problems in the littoral, as facilitated by organization of biophysical parameters into a coherent whole or universal scheme. The developmental approach to a new comprehensive classification system is thus proposed for the coastal fringe, a swath zone 5 to 10 km wide across the shoreline, which incorporates all important parameters necessary to categorize geomorphic units that can be mapped at meaningful scales. Consideration of coastal geomorphological properties are the theme of this approximation toward a modern taxonomic system where morphostructures are the unifying links that facilitate transition from one hierarchical level to another. The proposed approach employs differentiating criteria for hard rock (automorphic) and soft rock (allomorphic) coasts which are divided by chronometric parameters related to the antiquity of littoral landforms. Other levels of primary differentia include geodynamic-climatomorphogenic process zones, relief types (morphoregions), morphogenetic relief features, and relief elements and genetically homogeneous surfaces. Morphotypes are lower level taxons that provide examples of ingressional, egressional, and complex process-forms. The proposal for a unified system requires testing in the field and mapping at myriametric scales to update subsequent approximations.

The principle objectives of maritime engineering fall broadly into two classifications: (1) transportation, and (2) reclamation and conservancy.

Remote sensing of coastal marine environments has long challenged coastal researchers who have searched for automated methods based on supervised classifications. Due to complexities in water clarity and attenuation of spectral reflection with water depth, this study focused on visual interpretation of IKONOS satellite images in an effort to ascertain the general nature of bottom types. Development of a seafloor topology for a portion of the Key West National Wildlife Refuge in Monroe County, Florida (between Key West, Florida, and the Dry Tortugas) resulted in 96 mapping units. The natural complexity of this environment required classification units that were defined by numeric codes that were keyed to a classification system developed for this area. These units, defined in a stepwise procedure, were predicated on the geomorphologic base, context of the geomorphological zone, biological cover, and percentage of that cover. The GIS attribute table, built with a multi-discipline interpretation in mind, was constructed to allow end user flexibility when extracting the information related to major biological cover, detailed geological cover, etc. Suffixes were added to further interpret areas with diverse biological cover. The IKONOS satellite images were found to be useful tools for mapping coastal marine environments at a nominal scale of 1:6000.

Airborne laser bathymetric (ALB) systems rapidly acquire large, high-quality datasets via variable swath widths that are independent of water depth. Laser bathymetric survey tools have applicability in clear coastal (Case II) waters down to 270 meters depth. Deployed along the southeast Florida (Palm Beach, Broward, and Miami-Dade Counties)coast, an advanced ALB system provided a continuous dataset for 160 kilometers of coast from onshore to 6 kilometers offshore. Digital terrain models developed from this high-density bathymetric data permitted recognition of numerous seafloor features and bathymetric patterns from different image formats. Bathymetric analysis of the 600-km2 survey area on the narrow continental shelf shows inherited lithologic features that are partly covered by surficial sediments. Primary parabathic provinces include: (1) nearshore rocky zones dominated by the Anastasia Formation, (2) coralalgalreef systems (Florida Reef Tract [FRT]), and (3) marine terraces. Secondary sedimentary subprovinces include shoreface sands, inter-reefal sedimentary infills (coral rubble in basal sequences and near reef gaps), and finer-grained materials seaward of the FRT. Tertiary topographic features include: (1) longshore bar and trough systems, shoals, sand sheets, and diabathic channels; (2) reef crests and ledges, forereef spurs and grooves, sediment ramps in large reef gaps, and incised paleo-river channels; and (3) drowned karst topography. Hierarchical organization of these bathymetric features is now possible for the first time because of the increased accuracy and density of bathymetric data obtained by ALB systems.

Submarine morphological features along the southeast Florida coast in central Palm Beach County were mapped from large-scale aerial images (acquisition scale 1:3900) that permitted feature resolution in water depths of 10 to 15 m. The analog stereo-paired images were scanned to black and white digital images that were georegistered for inclusion in a spatial analysis program. Interpretive techniques for identifying submarine morphological features on the inner continental shelf were developed by adapting methods of aerial photointerpretation to computerized onscreen digitizing. This narrow coastal zone tract (up to 500 m in width) contained coastal-marine forms developed in the local limestone bedrock and unconsolidated sediments. Hardground features included rock reefs (exposure of the local Anastasia Formation) and coral-algal reefs of the Florida Reef Tract. In addition to common types of marine platforms and benches, rock reefs and para(dia)bathic hardground stringers are described here for the first time, as are structurally controlled sandflats. Sedimentary features included bars and troughs in addition to various types of soft bottoms. The amalgamation of similar submarine morphologies into morphodynamic zones spatially delineated the impacts of coastal-marine processes during the most recent stabilization of sea-level rise during the last few thousand years of the Holocene. Analysis of the spatial distributions for the various morphological types shows distinct zonations alongshore and cross-shore in terms of the forcing hydrodynamic processes. Karst morphologies of the coastal landscape drowned by the Holocene rise in sea level configure much of the seafloor and prefigure many coastal forms. Lithology exerts a strong control over the spatial arrangement of morphological features, which are seen as repetitive occurrences of similar morphological groupings. Distinctive coastal process zones, based on principles of form and function, define the Beach Depositional Zone (BDZ), bar-and-trough Inshore Depositional Zone (lDZ), sandflat Offshore Depositional Zone (ODZ), Offshore Erosional Zone containing hardgrounds (OEZ), Parabathic Transport Blockers (PTB) comprised by inlet diabathic processes, and Diabathic Transport Blockers (DTB) containing shore-parallel barrier reefs.

Chronic erosion of beaches along the eastern Texas barrier island coast is increasingly mitigated by renourishment efforts that periodically place large volumes of sand onshore. Location of beach-quality sands on the inner continental shelf is challenged in an environment where terrestrial rivers deposit fluvial sediments in back bays and lagoons instead of offshore and by shelf areas that are dominated by muds. The search for beach-quality sands thus requires understanding of the coastal geological framework and morphodynamic processes that accompanied late Quaternary evolution in the northern Gulf of Mexico. The occurrence of surficial sand deposits as positive bathymetric features on the seafloor (ridges, shoals, banks) and presence of sands buried in paleovalley (drowned channels) infill sequences makes for complicated search procedures that must accurately differentiate a range of sedimentary settings by geophysical and geotechnical surveys. Compilation of vast amounts of data from historical core logs and newly acquired information in a marine information system (MIS) permits spatial analyses in a format that is compatible with development of a sand search model. The resulting differentiated investigative sand-search methods, that comprise part of the Texas Sand Search Model (TSSM), are able to target potential borrow areas in ebb-tidal shoals, low-relief ridge deposits, high-relief banks, and in mud-covered paleovalley sequences.

The subtropical Atlantic coastal zone of southeastern Florida supports nearly 7 million inhabitants on a coastal plain conurbation that stretches from West Palm Beach to Miami. About a quarter of the present population originally settled on higher topography along the shore-parallel Atlantic Coastal Ridge. From about the middle 1900s, however, urbanization intensified along the shore and spread westward into freshwater marshlands. Population densities approaching 2500 persons per km-2 along some coastal sectors and dredge and fill operations to create urban land in western marshes degraded coastal environments bringing in question sustainability. Efforts to maintain environmental integrity initially focused on shore protection first via "hard" engineering works, which later on included massive beach renourishment projects along developed coasts subject to critical erosion. Marine algal blooms, led to eutrophication, degraded coastal water quality, and deterioration of coral reefs indicate environmental problems at least as serious as beach erosion. Recognition of a potential eco-catastrophe, collapse of entire marine and coastal wetland ecosystems in southern Florida, led turn to the Everglades Restoration Project, the largest single environmental recovery effort in the world. Cleanup of terrestrial systems is essential to sustainability of marine ecosystems now jeopardized by nutrient loading.

Differentiation of continental shelf morphology along the southeast Florida Atlantic coast was based on interpretation of airborne laser bathymetry. The 600-km2 shelf study area, which had a shoreline extent of about 160 km and extended up to 10 km offshore, displayed a diverse range of seafloor morphologies that were characteristic of four main alongshore reaches. Reach I (sand flats and karst topography) in the northern part of the study area is terminated southward by the Bahamas Fracture Zone, a major morphotectonic feature. Reach II (sand flats and coral reefs) is characterized by sand flats with diabathic channel fields leeward or shoreward of the Florida Reef Tract, the seaward margin of which occurs along the shelf break on the upper part of the continental slope. Reach III (sandflats, hardgrounds, and coral reefs) is characterized by extensive nearshore rock outcrops that are exposed as bare rock surfaces on the seafloor or are variously mantled by thin veneers of sand that are not thick enough to disguise the underlying rock structure. Reach IV (tidal sand flats and ridges, hardgrounds, and coral reefs) is dominated by tidal features that notably include fields of tidal sand ridges in the lee of the Florida Reef Tract. The barrier reef on the southeast Florida Atlantic coast, which transitions to Florida Keys shelf environments southward, grades northward to drowned karst topography that is overlain by sand sheets and sand waves. Tidal channels and associated bars, deltas, and shoals occur on the interface between Biscayne Bay and the Atlantic Ocean. This reconnaissance level characterization of continental shelf environments into morphological reaches in a geographic information system platform provides a basis for quantifying spatial distribution patterns of discrete landform units.

This paper reviews physical, geologic and environmental parameters of Louisiana barrier islands to support the definition of regional strategies and management practices for long-term coastal restoration. For management purposes the barrier island systems of Louisiana are divided into a series of coastal segments to be maintained over the long term. Recommendations are drawn for each coastal segment on the basis of biophysical properties. Two separate design approaches for barrier island restoration are elucidated (stable location design and retreat design) including sediment volume requirements for the restoration of specific barrier islands. In order to maintain long-term stability, intensive restoration programs require barrier island nourishment, vegetative plantings, and coastal structures in some cases. Restoration strategies, practices, and design approaches are refined by employing monitoring data in an adaptive management process.

Because of the large volumes of sand required for beach renourishment, dredging from offshore borrows is the preferred method of sediment supply. As easily accessible and previously known (obvious) deposits are exploited, apparent sand reserves are seen as a dwindling resource that becomes more precious over time. Because economically exploitable offshore sand sources are limited in many regions, renewed efforts are underway to locate additional offshore sand sources that can supply sand and mixed sediments (sand, silt, and clay) to barrier-island restoration efforts in Louisiana. Sediment volumes required for beach renourishment and marsh restoration are variously estimated on the basis of numerous assumptions to range in the extreme from 14 X 106 m3 to 71 X 106 m3, respectively, for one complete restoration of the entire barrier island chains. Although estimates of required volumes are controversial, significant new borrow sites must be located on the continental shelf off Louisiana to restore the barrier islands. The search for new sand sources must be focused on logistical procedures that are economical and efficient in order to cover large areas of the shelf in a timely manner. Sand search protocols developed for US East Coast sedimentary environments are broadly applicable in a conceptual sense but need to be adapted to deltaic coastal frameworks in Louisiana. Procedures and protocols for the Delta Sand Search Model (DSSM) are thus based on bathymetric, geophysical, and geotechnical survey recommendations for the identification of targets that will be proven out by detailed studies and cultural resource investigations. Development of a DSSM has advantage because it is specifically adapted to coastal marine morphosedimentary units in different-aged lobes of the Mississippi Delta that have fine-grained (muddy) deposits interspersed by sandy deposits of paleodistributaries and interdistributaries.