Northeastern Section - 36th Annual Meeting (March 12-14, 2001)

From 1989 to 1992 the US Army Corps of Engineers Presque Isle Erosion Control Project constructed fifty-five offshore segmented breakwaters with along the Lake Erie perimeter of the 11 km (7mi) recurved spit which is Presque Isle State Park (PISP) at Erie, PA. The purpose of the $23.8 million breakwater construction was to reduce the annual $ 1,000,000 expense of nourishment. Assuming success, the annual nourishment for 1993 to 1998 was reduced from 228,000 to 86,000 tons (38% of the pre-construction volume). This proved inadequate as evidenced by the failure of the distal end of the spit, called Gull Point, to grow at least 0.4 acres per year from 1996 to 1999. Massive sand nourishment (54 thousand tons)was deemed necessary and occurred from July to September 1999. The present study extends to a full year the monitoring study reported at the 1999 NEGSA for the fall and winter of 1999 –2000. The area from the back-beach offshore to a depth of 4 m (13 ft) was mapped periodically from October 26, 1999 through October 15, 2000. Shoreline changes and volumetric cut-and-fill analysis of subdivisions of the map area provide detailed information of offshore and along-shore movement of the nourishment sand. Ten north-to-south transects were mapped covering 340 m (1120 ft) of nourishment area and 600 m (1800 ft) downdrift from the back-beach offshore to a depth of 4 m (13 ft). The exposed beach and the lake bottom at an offshore buoy was mapped with a Lietz Total Station infrared laser theodolite. The deeper subaqueous portion, from the buoy lakeward, was surveyed with a Lowrance X-16 precision depth recorder. Contour maps were generated using Lietz’s proprietary Sokkia Map and Contours software. Sokkia Volumes software were used to calculate volume changes over time by comparing the surfaces thus mapped. ArcView GIS Spatial Analyst and 3-D Analyst will also be used.