What Might Happen to America's Shorelines if Artificial Beach Replenishment is Curtailed: A Prognosis for Southeastern Florida and Other Sandy Regions Along Regressive Coasts

Abstract

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.