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SEBASTIAN <br />INLET <br />A" �l� <br />R-1 <br />SEBASTIAN <br />sJLET <br />STATE <br />jECREATION R-10 <br />AREA <br />AMBERSAND <br />WABASSO <br />BEACH <br />SR 310`' <br />INDIAN <br />RIVER <br />SHORES <br />sit so <br />VERO <br />BEACH <br />SHORELINE CHANGE RATE <br />(FT/YR) <br />SHOAL AREA <br />R-100 �---- r' <br />R-110 I <br />N3 W A U1 0) <br />DIRECT INLET <br />IMPACTS <br />TRANSITION. <br />�k —118 I • I 1 <br />AVERAGE SHOREUNE CHANGE 1972-1986 <br />FIGURE 2 <br />Coastal Process Model <br />The offshore reef/ rock outcrop system is believed to be playing <br />a key role with respect to the beach processes. Its location <br />offshore and its shallow water depth probably contribute to its <br />performance as an offshore sill. This sill holds the toe of the <br />beach slope in place. Thus the beach profile above the reef/ outcrop <br />surface is significantly more stable than the sandy bottom slopes <br />located offshore of the reef/outcrop system. <br />Sand appears to be moving well along the coast in two shore <br />parallel paths separated by the reef/outcrop system. Inshore of the <br />reef/outcrop system, losses of sand to the inlet significantly <br />affect the northern portion of the County. The losses to the inlet <br />are compensated for by increased shoreline erosion over about 8.2 <br />miles of Indian River County coast. The sand continues to be <br />transported down the coast with beach eroded sand contributing along <br />the way to the overall volume of sand in transport. Deposition of <br />the nearshore sand stream begins in the shadow of the offshore shoal. <br />Down coast of the shoal, the erosion process resumes again, although <br />the erosion rate is lower than in other eroding areas of the County. <br />Sand is also moving from north to south in the areas offshore of <br />the reef/outcrop system. Erosion rates are about 5 times as great as <br />those which occur inshore of the reef. Although accurate profile <br />surveys do not extend further than 3,000 feet offshore, it is <br />suspected that some of the sand in transport in the offshore stream <br />is deposited in the shoal area. <br />The offshore reef/outcrop is an important factor in beach <br />behavior in response to storm wave activity. Its relatively shallow <br />depth and broad width reduce some of the wave energy which can reach <br />59 <br />AUG 161999 BooK 73 i,''u, 499 <br />