UPPER BEACH REPLENISHMENT PROJECT RELATED

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1 ASSESSMENT OF SAND VOLUME LOSS at the TOWNSHIP of UPPER BEACH REPLENISHMENT PROJECT RELATED to the LANDFALL OF HURRICANE SANDY - PURSUANT TO NJ-DR 4086 This assessment is in response to Hurricane Sandy that made landfall in New Jersey October 29, The damages to this part of the Cape May County shoreline were included under FEMA Category G guidelines in a Presidential Disaster Declaration made October 31, The Township of Upper completed a 688,000 cubic yard beach restoration project in cooperation with the New Jersey Department of Environmental Protection (NJDEP) during the late summer of The extent of the work ran from the municipal boundary with the Corson s Inlet State Park, 100 feet north of Seaview Avenue, extending south to the boundary with Sea Isle City. The design template called for a dune along the oceanfront with a crest elevation of feet and 5:1 seaward and landward slopes to the beach. This dune would be added to the existing dune if the existing dune was less than the specified height and volume defined for the project. If the existing dune equaled or exceeded the specified dune, no work was to be done to increase it. The berm was to be 100 feet in width at elevation 6.75 feet NAVD88 seaward of the dunes with a 30:1 slope further seaward to the limit of fill placement. This project extended south into Sea Isle City under a separate contract. Northeast storms in 2009 and 2 in 2010 resulted in restoration work completed during 2011 with a sand placement project to restore the Ludlam Island beaches from damage suffered over the course of three events (November 2009, March 2010 and December 2010) that commenced in the fall of Sand was pumped from Corson s inlet ebb-tidal delta onto the NJ Corson s Inlet State Park, the oceanfront municipal beach of Upper Township and via a booster pump sand was moved south into Sea Isle City to provide recovery material for that community. The relatively low rate of losses from two events (Hurricane Irene and a northeast storm October 29, 2011) were ignored. The repair project was about to start as Hurricane Irene occurred, which prompted a decision to accept the modest losses rather than delay the project while the FEMA bureaucracy labored over combining the existing losses with the two recent disaster declarations in what was termed a roll-over declaration summary. Restoration sand was placed on the beach, surf zone and nearshore on northern Ludlam Island within the State Park and Township boundaries. In addition, sand was placed on the beach and nearshore at the Township s central and southern oceanfront from approximately Survey Line to the municipal boundary with Sea Isle City. The restoration project was completed in January The final reported project volumes within the design template as provided by Weeks Marine Co. were 132,674 CY added to the north end Natural Area and 315,940 CY to the Township beaches. The CRC survey s showed a total of 590,916 CY of sand was added to the region, including changes occurring offshore beyond the project design template limits. Hurricane Sandy occurred exactly one year after the last storm to impact the NJ coast. There were no storms to record between October 29, 2011 and October 29, 2012, so beaches retained or added to the sand volume on the beach as the wave climate acted to push material landward from offshore. The CRC crew returned to Strathmere following Sandy and completed a review of each of the 200-foot spaced transects from the dunes,

2 across the beach and into the water offshore. This was completed between November 2 and 6, The Township of Upper municipal beach would require 103,410 cubic yards of sand to restore the project to the original design s elevation and width parameters. The NJ State Park would need 10,270 cubic yards of sand to perform a design restoration. These sand volume figures are based on the Digital Elevation Model using the original design criteria for elevation of the beach, width of the beach and dune system, compared to the beach following Sandy (Figure 8). There were multiple areas where accretion of sand had raised the beach elevation or dune width to levels exceeding those of the engineering design. These losses were computed, but subtracted for the values given in Figure 8. Figures 5, 6 and 7 display the various computations for the total storm losses (Figure 6) when compared to August 2012 survey data. This loss was larger because it includes those areas where the design template elevations or widths were exceeded (The NET loss was 128,191 cubic yards across the municipal shoreline and -31,162 cubic yards in the NJ State Park area). Taking the August data, the design parameters and the post-storm Survey information, the sand losses due to Sandy, that were within the design template conditions and therefore reimbursable under DR-NJ 4086 were those shown in Figure 8 (103,410 cy and 10,270 cy). The CRC employed a Leica Total Station system and RTK GPS equipment and had personnel take points along survey lines established for the control of sand placement for the project from the baseline across the dune areas, the beach and into the water to a depth of 10 to 15 feet. The project baseline for the municipal project was established during the design phase as the Centerline of Commonwealth Avenue, which runs parallel to the oceanfront beach. The Corson s Inlet State Park area was surveyed using 11 inlet lines and stopped the park s sand volume calculations at the northernmost oceanfront survey line (Line 37+80). There are 46 oceanfront survey lines spaced at 200-foot intervals. The CRC surveyed all 46 lines between the State Park boundary and Line at the Sea Isle City municipal line. All cross section plots are provided in this report along with computation tables defining the pattern of loss. Grainsize Information on the Project Beach: The Coastal Research Center completed sediment sampling at the Township of Upper, NJ site on June 18, 2009 (pre-beachfill) and August 25, 2009 (post-beachfill). Previous documentation presented for DR-NJ 1867 showed that the borrow zone sand from the ebb-tidal delta of Corson s Inlet was essentially identical in size (0.22 mm Mean), distribution and mineralogy to the native beach. The sampling prior to and following the initial project showed that the mean grainsize increased by 0.10 mm on average. These results were obtained from four beachface samples repeated following sand placement. These results would be expected since the coastal processes at work distribute beach sediments continuously into and out of the ebb-tidal shoals surrounding any New Jersey inlet. This is particularly true at Corson s Inlet since there are no man-made structures present to restrict or direct sand transport into or out from the inlet area (Storm Assessment for DR- NJ 1867 for the Township of Upper). Map and Cross Section Information: In order to determine the sand volume loss attributable to Hurricane Sandy, the August 15, 2012 survey done six months following restoration work described above was compared to a post-storm survey from November 6, This direct comparison yields a sand volume loss of 271,200 cubic yards of sand lost from the entire project due to Sandy. The Corson s Inlet State Park lost 36,526 cubic yards while the municipal oceanfront shoreline lost 234,674 cubic yards. The loss was derived from the beach by reducing its elevation and from the seaward toe of the dune system. There was little evidence for direct overwash inland until south of the boundary with Sea Isle City. A digital elevation model (DEM) of the beach will show the changes brought on by Hurricane Sandy. 2

3 Photographs Before and After Hurricane Sandy; Aerial views were obtained from a private pilot/photographer in late June and November 2012 immediately following Hurricane Sandy. The ground pictures were taken by the field crew as the survey work progressed. The June 30, 2012 photograph shows a wide, dry beach along the majority of the Strathmere shoreline. In addition, the natural area at the northern tip was also well protected b y a double recurved spit, one attached to the shoreline and a second curving around into the inlet making a second wave and tidal current-built feature attached to the oceanfront beach and extending the width of the island landward. Large shoals surrounded the main tidal channel and acted to force waves to break far offshore from the dunes. The November 5th flight shows that Sandy scoured the wide, dry beach removing a great deal of material from the berm and expended the last of the storm s energy as transport into the dunes. Some dune erosion occurred, but little overwash into property or streets occurred. Tidal flooding was the dominant form of storm damage. Beach recovery was already started as the November 5th photograph shows a continuous line of bars parallel to the low tide line in the photograph. Sand transported offshore was beginning to move landward after the storm waves subsided. 3

4 Figure 1. Aerial view of the northern segment of the Upper Township beach including the State Park section north of the homes on the inlet. This view taken June 30, Figure 2. View of the Strathmere beach at the north end of Commonwealth Avenue November 5, The wide beach acted to protect the dunes from Hurricane Sandy, which, in turn, protected the public and private development from damage. Most of the inlet park land was reduced in elevation but the outline remains the same. Bars where already appearing at the low tide line. 4

5 Figures 3 & 4. Two views of the northern beach segment looking south from Williams Avenue on November 6, The lower view was taken at the low tide line showing small bars of sand building on the incredibly flat beach left by the storm. The top view shows the sand transported into the dune grasses where the storm s energy was finally absorbed without damage to the homes. 5

6 Figure 5. Digital Elevation Model for the Township of Upper beach and NJ Corson s Inlet State Park following Hurricane Sandy. The early November data were surveyed over 4 days between November 2 and 6, The NJ State Park is outlined in red and the remainder of the map depicts the Township oceanfront shoreline. 6

7 Figure 6. This Digital Elevation and Sand Volume Change map is based on the comparison of pre-sandy information obtained in August 2012 and compared to the post-storm information from November. The volume calculation was compiled for all areas to the crest of the dune system seaward across the beach to an elevation of -2.0 feet NAVD88. This zone of loss amounted to a gross loss of 172,763 cubic yards mitigated by areas of gains totaling 44,572 cubic yards of sand. The NET loss was 128,191 cubic yards across the municipal shoreline and -31,162 cubic yards in the NJ State Park area. 7

8 Figure 7. The initial design used for the initial construction of the engineered beach in Upper Township called for specific elevations for the beach (+6.75 feet NAVD88), specific widths to the beach (100 feet except for the northeast corner of the project) and a 1:25 slope seaward to the limit of sand flow. This set of criteria is termed the Design Template for the beach. This digital elevation model displays the comparison of the Post-Sandy beach/dune system to the surface created by the design for the beach. The sand volume needed to return to the design is 242,150 cu. yds. for the municipal beach and 39,490 cu. yds. for the NJ State Park area. 8

9 Figure 8. Since the design template determines an absolute limit for potential FEMA reimbursement for damages associated with DR-NJ 4086, the sand present in excess of the design template cross section just prior to Sandy has been excluded from this computation. Only the sand between the design template cross section and the post-sandy beach configuration is shown in this final figure. The Township of Upper municipal beach would require 103,410 cubic yards of sand to restore the project to the design s elevation and width parameters. The NJ State Park would need 10,270 cubic yards of sand to perform a design restoration. 9