8/16/1988 - Laserfiche WebLink

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L—J i Beach Erosion M Figure 1 summarizes the overall changes which have taken place on the County's beaches over the period of 1972 - 1986. It illustrates idealized beach profiles representing the 1972 and the 1985/1986 conditions. On the upper portions of the beach (elevation 10 ft), the profiles show a general erosional condition. At the elevation 0 ft shoreline, the profiles show a general seaward movement. These changes on the "dry beach" portion of the profile are indicative of storm erosion changes wherein the beach takes on a lower, flatter form. Over the period, the "dry beach" has lost about 60,000 cubic yards per year for the entire Indian River County shoreline. Figure 1 also indicates the changes which have taken place in the submerged portion of the profile. On the average, the profile change tends to be accretional in the shallow water section. In water depths of 10 ft and greater, the profile change becomes strongly erosional. The average loss for the entire County shoreline amounts of 656,900 cubic yards per year or about 5 times as great as occurs in the dry beach portion of the profile. Most of this loss is occurring in water depths of 10 feet and deeper. Figure 2 indicates the variation in erosion rates along the County shoreline. It shows the actual variation at each of the survey monuments and also shows a smoothed line which represents the average erosion trend along the coast. The period of change as represented in the figure is the 13.5 year period from November 1972 to June 1986. The average erosion trend line shown in Figure 2 shows the influence of the major coastal features which were discussed above. Clearly evident are the segments of the coast affected by Sebastian Inlet and the large offshore shoal. 20 10 0 Z Z 0 —10 W J W —20 —30 cc1 W m AVERAGE PROFILE CHANGES 1972-1985/1988 . AUG 161998 58 ROFILE R TOTAL 'ROFILE 'YR FIM IDC 1