Figure 4. View north at Jupiter site, 6 May 1970; 2 hours 



before high tide (H = 5 ft, T = 7.0 s, a^ = 15°). 



The site is 13.7 miles (21.9 kilometers) south of St. Lucie Inlet, 

 and 1.3 miles (2.1 kilometers) north of Jupiter Inlet. A small protu- 

 berance of the coastline occurs about 800 feet (245 meters) north of 

 the site. It is about 800 feet in length and extends about 200 feet (60 

 meters) seaward from the general trend of the shore. This protuberance 

 appears unchanged in both position and magnitude on the U.S. Geological 

 Survey 1967 photo revision of the 1948 7.5-minute series topographic map 

 of the Jupiter quadrangle. The feature is probably the result of the 

 resistant coquina limestone which crops out just below MSL. More pro- 

 nounced exposures of coquina (Anastasia Formation) occur above MSL, about 

 1 mile (1.6 kilometers) north (Puri and Vernon, 1964). The large amount 

 of shell fragments on the beaches in this area has been attributed to the 

 gradual erosion of local coquina outcrop (U.S. Army Engineer District, 

 Jacksonville, 1965; Meisburger and Duane, 1971; Field and Duane, 1974). 



The beach at the Jupiter site is steep and narrow, with a typical 

 width from the MSL shoreline to the toe of the frontal dune of 100 feet 

 (30 meters) and a 1 on 10 slope (Fig. 3). A steep dune face with a maxi- 

 mum elevation of about 20 feet (6 meters) backs the beach. An abandoned 

 asphalt roadbed occupies the crest of the dune and is being undermined by 

 slumping of the eroding dune face. There has been minimal real estate 

 development in the immediate vicinity; the nearest community, Jupiter 

 Inlet Colony, occupies the southern one-half mile of Jupiter Island. 

 Numerous seawalls, sloping revetments, and groins have been constructed 

 by local interests in the town of Jupiter Island to the north. Tlie town 

 began an artificial beach nourishment program in 1956; about 700,000 



16 



