Suchergebnisse

This book covers the gamut of coastal hazards that result from short-term low-frequency events and have high-magnitude and far-reaching impacts on coastal zones the world over. Much of the world's population now lives in low-lying coastal zones that are inherently vulnerable to natural hazards such as flooding from hurricanes, tropical storms and northeastern storm surges; shoreline (beach and dune) erosion; cliff and bluff failures; and saltwater intrusion in coastal aquifers used for drinking water supplies. In addition to the usual range of hydrometeorological disasters in coastal zones, this book covers tsunami impacts and warning systems as well as global perspectives of sea-level rise impacts and human perceptions of potential vulnerabilities resulting from rip currents that cause many drownings each year on beaches. Today, the use of numerical models that help predict vulnerabilities and provide a basis for shore protection measures is important in modern scientific and engineering systems. Final considerations focus on human actions in the form of the urbanization and industrialization of the coast, shore protection measures, and indicate how environmental degradation around coastal conurbations exacerbates the potential for unwanted impacts. Strategies for environmental management in coastal zones, from low-lying wetlands to high cliffs and rocky promontories, are highlighted as a means of living in harmony with Nature and not trying to conquer it.

Beach replenishment in Florida consumes about one-third of what the federal government spends nationally on battling coastal erosion. Recent proposals from Washington are to cut the federal share of hurricane and storm surge protection, inlet maintenance, sand bypassing, beach restoration, and periodic renourishment projects in Florida. Although Florida has more beach erosion control projects than all the other states combined, erosion is still a problem for some 700 km of shore and has reached "critical" levels along 370 km of Florida beach front where development or recreation are threatened. Of 215 km of erosion that have been studied, 140 km have been restored; the remainder has been abandoned because erosion rates are too high. If the average federal 50% cost-share for coastal protection is eliminated, local governments will have to support future projects at a minimal rate of $20-40 million per year. The annual cost of shore protection is modest compared to income generated by beach-related activities in Florida which overall bring in about $1.5 billion in annual sales. Alternative proposals to forego beach renourishment altogether, because it is "too expensive," suggest that new lines will be drawn in the sand for construction control and erosion setbacks. Due to relative sea-level rise (which includes land subsidence), natural background shoreline recession rates for the Florida Atlantic coast now average between 0.3-0.4 m a-1. Accelerated rates of coastal erosion are associated with beaches backed by seawalls and coastal segments lying downdrift from stabilized inlets. Because jetties are littoral drift blockers, they are responsible for about 85% of Florida's beach erosion problem. Erosion fronts, which migrate downbeach from jetties at a rate of about 1 km a-1, can quickly impact long coastal segments in a few years. Just south of the Port Everglades inlet, for example from DEP monuments R86-R91, beach fill placed in 1989 eroded 60 m in 6 years for an annual shoreline recession rate of 10 m a-1, or a volume loss of 10 m3 m-1 a-1. Additional erosion hot spots occur downcoast from other trained (jettied) inlets and elsewhere along the coast. With the present total annual net loss at 3-5% by volume of beach sand in Broward County, about two-thirds to one-half of the Atlantic dry beach width will remain within s decade, by around 2007. This new line in the sand will reflect loss of both artificially replenished beaches and natural beaches alike. Without replenishment, the volume of eroded beach sand in Broward County alone will probably amount to something on the order of 5.2 x 106 to 8.6 x 106m3. This magnitude of unrecovered decadel sand volume 1088 translates into future problems of greater magnitude than exist today. Salient among them is the prospect that fewer tourists will visit narrower, eroded beaches and the Florida economy will realize significantly leas income from a major but declining economic resource. A management policy of 'no new beach replenishment activities' will in the first decade: (1) cause accelerated loss of beaches, (2) place a larger proportion of the coastal population at risk from flooding, (3) increase vulnerability of coastal infrastructure to floods and inundation, (4) decrease revenue from tourism, and (5) result in higher costs for future shore protection. The proposed federal policy would be environmentally shortsighted, fiscally irresponsible, and negligent of proper methods of beach management. It is perhaps ironic to note that America has no national shore protection policy, that sand has become a restorrative resource of choice (opposed to hard, structural stabilization methods), and at a time when sand resources on the outer continental shelf may become available for beach renourishment, the Clinton Administration is proposing to put the brakes on soft shoreline stabilization.

The Dalmatian coast has been described by an occasional poet as the site where chalk and sea meet. If in frequent political turmoil, it also has shown to be equally an area of frequent geomorphologic events. The riparian countries have been trying, with some success, to make a tourism trump of what Emmanuel de Martonne appropriately labelled une côte morcelée. The paper focuses on the region's significance as a geomorphology "textbook". ; Department of Geosciences Charles E. Schmidt College of Science