FINAL REPORT FOR 2011 ON THE CONDITION OF THE MUNICIPAL BEACHES IN THE CITY OF BRIGANTINE BEACH, ATLANTIC COUNTY, NEW JERSEY

Transcription

1 FINAL REPORT FOR 2011 ON THE CONDITION OF THE MUNICIPAL BEACHES IN THE CITY OF BRIGANTINE BEACH, ATLANTIC COUNTY, NEW JERSEY Photograph was taken October 10, 2011 from 10 th Street North looking south along the north end promenade towards the end of oceanfront development. The beach was under construction as part of the 2011 ACOE maintenance project that placed sand on the oceanfront beaches from the natural area just north of 14 th Street North to a taper south of 6 th Street North. Placement of the project sand hauled to the site by trucks from a mainland quarry is dumped then spread by bulldozers along the beach seaward of the promenade. Prior to the project sand had eroded to the base of the revetment exposing rocks and limiting beach access in the region. This maintenance project has restored a marginal recreational beach along the promenade revetment, buries the exposed rocks, improves shore protection and allows easier access to the beach. PREPARED FOR: THE CITY OF BRIGANTINE BEACH 1417 WEST BRIGANTINE AVENUE BRIGANTINE, NJ PREPARED BY: THE RICHARD STOCKTON COASTAL RESEARCH CENTER 30 WILSON AVENUE PORT REPUBLIC, NEW JERSEY DECEMBER 2, 2011

2 TABLE OF CONTENTS Introduction 1 Municipal Beach Profiles 1 Table 1: Beach Profile Locations 2 Second Half Changes 2 Table 2: Second Half 2011 Beach Volume & Shoreline Changes 3 Changes Since November Table 3: Annual Beach Volume and Shoreline Changes 4 Individual Profile Site Descriptions Including Figures 1 to 9 (Photographs) 5 Absecon Inlet Jetty Erosion Study 11 Digital Elevation Model 12 Figure 10. Digital Elevation Model of Absecon Inlet 12 Shoreline Migration 13 Figure 11. November 25, 2011 aerial photo of Absecon Inlet area 13 Figure 12. Shoreline Positions 1995 to Inlet Study Summary 14 Figure 13. Cumulative Shoreline Changes at the Absecon Inlet Jetty 15 Conclusions 15 Figure 14. Comparison Plot for 43 rd Street South Between 1986 and Figure 15. Shoreline Trends for 27 th Street South Since Figure 16. Shoreline Trends for 43 rd Street South Since Figures 17-25: Municipal Survey Sites Cross-section Plots 20 i

3 Annual Report for 2011 to the City of Brigantine Beach on the Condition of Municipal Ocean Beaches Introduction: The winter storm season from fall 2010 through May 2011 was in dramatic contrast to the previous winter. Instead of 9 northeasters, there were 3 or 4 depending on the wind constraints used to determine an event as a northeaster. Basically, nothing damaging happened until August 28, 2011 when Hurricane Irene passed over the NJ coastline making the first hurricane landfall since The Brigantine City beaches remained relatively stable and generally accumulated sand across the majority of the shoreline. In the early fall of 2011 the US Army Corps of Engineers commenced hauling sand from an Atlantic County quarry on the mainland to augment the erosional section along the northern promenade between 6 th and 14 th Streets North and then tapered into the natural area. The use of trucks to bring quarry sand was the best method to place the relatively small sand quantity funded, well below the volume required to justify the mobilization cost of bringing in a dredge to Brigantine Inlet and placing several thousand feet of pipeline along the natural area beach. The negative aspect to the public of the trucked in material has been the aesthetics of the orange-yellow sand deposit on the beach leading to numerous complaints. The quarry sand has been sitting on the NJ coastal plain for over 20 million years, deposited long ago by a river system. Ground water dissolves iron as a soluble oxide that moves in solution with the water through the sediment. If the ground water surface in the sand encounters oxygen in the soil, the iron further oxidizes to a non-soluble mineral akin to rust (limonite). This material slowly coats the quartz grains of sand turning them yellow-orange. In sufficient time the coating fills the space between the grains of sand creating a cemented sandstone rock. Jersey bog iron stone is just such a product of accelerated cementation by iron oxide. Any home owner with a well is familiar with the iron stains associated with South Jersey well water sitting in the toilet tank, dripping into the sink or spraying from irrigation wells on the lawn. This coating will wear off in the surf zone over a few weeks time leaving a clean quartz sand beach once again. Digging deep into the beach will uncover un-washed sand, but few folks bother to do that. Four of the nine sites showed sand volume loss for 2011 and those losses were very minor. Gains between 27 th and 43 rd Streets South more than compensated for any losses elsewhere. The net sand volume increase in the City of Brigantine Beach was 228,007 cubic yards or about 9.1 yds 3 /ft. for each foot of Brigantine s beachfront. Field surveys were conducted on a semi-annual basis similar to those collected in The Coastal Research Center (CRC) completed the 9 quarterly beach monitoring profiles on the following dates: November 18, 2010 Survey 73 May 6, 2011 Survey 74 October 25, 2011 Survey 75 The Coastal Research Center (CRC) completed a beach erosion assessment at the Absecon Inlet Jetty under our 2011 contract with the City of Brigantine. On August 25 th, 2011 the CRC survey crew conducted a complete survey of the Brigantine shoreline adjacent to Absecon Inlet. The survey data were analyzed in ArcGIS software to generate a digital elevation model (DEM) of the area. A shoreline position change analysis was performed to determine shoreline migration rates from 1995 to These results are shown as a separate section at the end of this report. Municipal Beach Profiles: The Richard Stockton College Coastal Research Center established a coastal monitoring program for the City of Brigantine in June 1992, commencing research on the beaches between two major northeast events to affect the Jersey shore in October 1991 and December The program collects data from nine shoreline-perpendicular beach profile stations, initially monitored on a quarterly basis, to analyze beach changes. Starting in 2008 the program was resumed at a survey frequency of twice annually. 1

4 Beginning at a fixed reference position, a profile includes the dune system, beach, berm, nearshore and offshore to a water depth of approximately feet (NAVD88). The following table lists the Brigantine sites where cross sections, photographs and field notes are obtained. Table 1: Beach Profile Locations Brig North end Green Acres undeveloped area (NJBPN #134) Brig At the north end of the feeder beach, 1200 feet from road end Brig th Street North Brig 4-4 th Street North (NJBPN #133) Brig 5-5 th Street South Brig th Street South (NJBPN #132) Brig th Street South Brig rd Street South (NJBPN #131) Brig 1 - South Beach 600 feet north of the Absecon Inlet Jetty Second Half Changes: On August 27 th & 28 th Hurricane Irene swept along the eastern US shoreline causing beach erosion, property and infrastructure damage and extensive flooding from North Carolina to New England. The storm made a second landfall in New Jersey at Little Egg Inlet in Ocean County on August 28, 2011 just north of Brigantine. Hurricane Irene was by far the most significant storm event to impact the Jersey shore in Prior to arrival of Hurricane Irene the spring and summer weather patterns had produced an environment favorable for natural beach building processes. The beaches were either stable or accumulating sand on the beach. Cross-shore sand transport from the seafloor to the beach supplied abundant additional sand volume that added width and height to the summer beach berm providing an excellent recreational beach and significant storm protection for the dune system especially along the southern city beaches. Tropical storm force winds began to affect the Jersey coast on August 27 th by Saturday afternoon and continued to build to near hurricane strength by Saturday evening, as the outer bands of the storm came ashore. Ocean swells generated by the storm began to impact the Jersey coast Friday ahead of the storm. Predictions estimated the storm surge could be between 3-6 feet in New Jersey with wave heights reaching feet by Sunday morning. Irene made its second U.S. landfall near Little Egg Inlet in New Jersey near sunrise the morning of August 28, becoming the first hurricane to make landfall in the state since Irene was downgraded to a tropical storm as it made its third U.S. landfall in the Coney Island area of Brooklyn New York at approximately 9:00 am on August 28. Fortunately the storm was moving quickly as it passed New Jersey and was weakening with much of the storm s energy expended on the Outer Banks after an influx of dry air into the storm reduced its strength. Consequently the resulting storm surge and wave heights New Jersey actually experienced were on the lower end of the predicted range reducing the damages that potentially could have occurred from this storm. Because of the storms track and landfall over Ocean County erosion was more significant on the northern Jersey beaches than in south Jersey. At the north end the ongoing beach nourishment project that began after Hurricane Irene has masked any damages experienced during the storm. The project has provided about 5 feet of additional beach elevation and added about 50 feet of dry beach width seaward of the promenade. Upon its completion, the US Army Corps of Engineers project will have improved the erosional section from the north end natural area along the northern promenade to 6 th Street North. Table 2 below shows the fall sand volume changes in cubic yards per foot (yds 3 /ft) of beachfront and shoreline change measured in feet for each of the City's nine profile sites. Also included is a net volume change in cubic yards for the Brigantine beachfront. The total volume is calculated by averaging the volume change at adjacent profile sites, which is then multiplied by the distance between profile sites. 2

5 Table 2: Second Half Survey Comparison Brigantine Beachfront Sand Volume and Shoreline Changes May 6 to October 25, 2011 Profile Shoreline Volume Avg. Volume Distance Net Volume Change Change Change Between Change (feet) (yds 3 /ft) (yds 3 /ft) (feet) (yds 3 ) Brig ,122 26,709 Brig ,860 5,989 Brig ,951 10,545 Brig , Brig ,729-14,914 Brig ,042 38,770 Brig , ,049 Brig , ,114 Brig Absecon Jetty Total Volume Change = 334,332 A substantial volume of sand was added to the municipal shoreline during the second half of 2011 concentrated south of 15 th Street and in the northern natural area. The net change was a gain of 334,332 cubic yards that amounts to an additional yds 3 /ft. for every foot of Brigantine s 25,097 feet of shoreline including the majority of the northern Green Acres tract. Sites Brig-27 and Brig-43 had the most significant gains with nearly 35 and 39 cubic yards of sand per foot of shoreline added respectively to each with an expansion of the berm seaward and deposition in the near and offshore troughs raising the seafloor several feet. The sand was likely derived from offshore beyond the profile limits pushed landward by the hurricane swells generated during Irene. The northern Green Acres site also had a moderate gain adding yds 3 /ft of sand to the beach. The remaining sites all had modest losses or gains ranging from to 9.13 yds 3 /ft of sand. Brig-1 located near the Absecon Inlet Jetty was essentially stable during the summer. The storm activity seemed to focus its impact on the middle segment of the City shoreline with shoreline and volume losses at Brig-5 and Brig-15. The ongoing ACOE project along the north end promenade masked any impacts from Irene in this region. Changes Since November 18, 2010: Table 3 contains computations on shoreline changes and sand volume changes since the end of Beach restoration has had four episodes that starting in 1997, followed by restoration in 2001 (funding reimbursed by the Federal Emergency Management Agency (FEMA) following a limited storm disaster declaration for a northeast storm February 6, 1998), the initial Federal project in 2006 and finally the 3

6 current fall 2011 ACOE maintenance project. All together a little under 2.5 million cubic yards of sand have been placed on beaches along the northernmost part of the developed portion of Brigantine with feeder material placed on the undeveloped beach just north of the end of development to provide advance nourishment sand for the area around 12 th Street North. Table 3: Sand Volume and Shoreline Changes November 2010 to October 2011 Profile Shoreline Volume Avg. Volume Distance Net Volume Change Change Change Between Change (feet) (yds 3 /ft) (yds 3 /ft) (feet) (yds 3 ) Brig ,122 9,116 Brig ,860-23,603 Brig ,951 6,272 Brig ,805-8,384 Brig ,729-40,498 Brig ,042 33,918 Brig , ,660 Brig ,855 94,207 Brig ,681 Absecon Jetty Total Volume Change = 228,007 During the past year the City of Brigantine Beach shoreline gained 228,007 cubic yards of sand, the majority deposited between 15 th Street South and Brig-1. Over the winter the beach between Brig-1 and the Absecon inlet Jetty eroded with little or no recovery over the summer for a yds 3 /ft net loss and 59 feet of shoreline retreat. Brig-220 located on the feeder beach and Brig-5 near the middle of the City shoreline also had moderate sand volume losses of yds 3 /ft and yds 3 /ft respectively. Modest annual losses were also recorded at Brig-12 with a loss of -7.42yds 3 /ft and at Brig-15 where the beach lost yds 3 /ft of sand. Brig-43 had a significant increase in sand volume for the year adding yds 3 /ft of sand to the beach and offshore, expanding the shoreline seaward 59 feet and filling the nearshore trough. The beach at 27 th Street South also gained a significant quantity of sand advancing the shoreline 53 feet and increasing the volume by yds 3 /ft of sand deposited on the berm, nearshore and filling the offshore trough. Brig-134 and Brig-4 also gained modest amounts of sand increasing the beach elevations and seafloor. This year most of the southern shoreline beyond 15 th Street South gained sand while the middle of the island and northern sections along the promenade and feeder beach loss material despite material added by the ACOE to the promenade section. The project has created 60 feet of dry berm and a shoreline advance of 66 feet but offshore losses offset these gains for a net loss. 4

7 Individual Profile Descriptions: The beach changes measured between November 18, 2010 and October 25, 2011 are displayed below in photographs and as scaled profile comparison plots, (Figures 1 through 9), which follow the pictures and text. Profile Brig-134: Green Acres - North end (Figures 1a & 1b) The profile line is located 4,752 feet north of the seawall at the north end of Brigantine Avenue. The dune and vegetation landward of dune toe is all relatively new growth over the last two decades that followed major breeches and over wash during the Dec storm. No new sand was added to the site during any of the nourishment cycles, sand placement started on the feeder beach almost 3,500 feet further south. The development and promenade are barely visible in the left-hand photograph below. Figure 1. The left photograph shows the dunes and beach taken November 18, 2010 looking south following the long winter of multiple northeast storms in A dune scarp extended south with grass plants left at the base of the scarp. Slumping was minimal because these dunes built up naturally from the elevation of the beach so their roots extend the entire thickness of the dune. The right-hand picture taken on October 25, 2011 shows more slope modification as wind blown material accumulated along the dune toe restoring the seaward slope up to the top of the storm scarp. The old scarp is almost undistinguishable except for the abrupt end of the vegetation line. The November 18, 2010 beach configuration with its low elevation profile allowed storm wave run up to reach the dune toe and further erode the seaward slope, evident by the debris line along the dune toe. By May 2011 a return of calm weather patterns favorable for cross-shore transport and beach building processes resulted in sand moving onshore and restoring a small beach berm protecting the dune toe from further wave run up and erosion. The summer season continued this building trend and by October 25, 2011 the berm width and height had nearly doubled. By year end the sand volume had increased by 23.8 cubic yards of sand per foot of beach (yds 3 /ft) as sand moved both onshore to the beach and long shore to the south. Despite the landfall of Hurricane Irene this fall summer beach building dominated the processes at work for the net annual gain. Sand on a near shore bar is located in a favorable position to move onshore under calm weather conditions further enhancing the beach width and elevation before the start of the winter season. The beach berm at this site has been restored naturally after the winter storms of had eroded it completely and is now in good condition to provide adequate dune protection from wave run up in the event of a coastal storm. Profile Brig-220: Feeder Beach - Line (Figures 2a & 2b) The site is located on the feeder beach portion of Brigantine s engineered beach just north of the promenade on the natural area. The primary dune ridge pre-dates the beach project, but additional sand has accumulated on the seaward crest and slope, blown across the wide berm that remains from the initial and subsequent maintenance beach fill projects. The goal for this section of the beach was to provide an available sand source to erode and have material move south into the developed portion of 5

8 the project area to slow erosion in front of the revetment to a more sustainable rate and extend the project benefits for a longer period. This process has been documented to perform better than expected over the past 13 years. Figure 2. The left photograph shows the shoreline on November 18, 2010, there still is sand available to feed the beaches to the south, but the shoreline has retreated to the point where its position is nearly equal to the northern end of the revetment structure. The photo on the right taken on October 25, 2011 shows the expansive width of the feeder beach now depleted allowing higher tides to encroach closer to the dune. In the distance the yellow sand hauled to the beach from inland quarries during the ACOE project can be seen near the end of the promenade slightly tinting the sand from gray to tan in the tidal zone of the feeder beach. No sand was added directly to this site during the 2011 ACOE maintenance project. The project sand was limited to the promenade region with a small taper into the natural area well to the south of this location. The site has continued to shed sand south but is approaching a condition were this beach will no longer be able to loose sand without loosing storm protection for the dune system. Sand losses were modest along this beach in following the November 2010 survey ( yds 3 /ft.) with a minor 7-foot shoreline advance placing the shoreline position nearly in line with the revetment. The accumulated losses were not severe, but demand close attention going forward for a depleted feeder beach can no longer provide advance sand nourishment to the chronic erosional zone along the north end revetment. Profile Brig-12: 12th Street North (Figures 3a & 3b) This monitoring site was established June 1992 along the north side of 12 th Street North. The profile includes the promenade and bulkhead revetment structure that was completely reconstructed prior to the 1997 beach nourishment project. The Federal project placed sand here in February 2006, eventually adding yds 3 /ft. of sand to the beach. By December 2009 the rocks were exposed yet again, but a narrow dry beach existed during the summer. The November 18 th survey found that the dry beach was gone and waves reached the rocks at high tide. A chronic erosional region the shoreline and promenade are aligned to the northeast increasing its exposure to storm wave approach sweeping sand south during Nor easters. As the beach retreats to the promenade the rock revetment protection is exposed. The revetment tends to reflect far more wave energy than the beach, so return flow takes the beach elevation downward rapidly. Left unchecked the erosion spreads rapidly south along the revetment towards oceanfront development near 8 th Street North. The feeder beach is designed to prevent this from occurring by providing advanced sand nourishment to this region in order to maintain a minimal beach seaward of the revetment and prevent exposure of the hard structure. 6

9 Figure 3. The left picture was taken on November 18, 2010 the beach was lowered to the point where waves at high tide always reach the rocks. The old timber groin was re-exposed on the beach in the distance. Approximately 4 feet of additional rocks are visible at the end of By October 25, 2011, the ACOE project had restored a dry berm seaward of the rock revetment covering the previously exposed rocks. The Orange yellow tan tinted sand hauled from a mainland quarry has caused some concerns with residents over the aesthetics but over time the color will be washed and bleached out by the environment restoring the gray sand coloration most New Jersey beachgoers expect. The surprising rate of deterioration during the fall of 2010 meant that little dry beach existed in front of the rocks over the winter months. Fortunately the winter of 2011 was dominated by relatively calm weather patterns with no major coastal storm development. The weather pattern continued into the spring allowing some sand to move back onshore by May Over the summer natural beach building conditions continued and was augmented in the fall by the 2011 ACOE beach maintenance project restoring a dry beach seaward of the promenade and burying the revetment rocks. The project reestablished a dry beach berm that extended approximately 50 feet seaward of the promenade. The new berm added between 5 and 6 feet of sand vertically to the beach elevation. The net result for the year was a gain on the beach of yds 3 /ft. and 66 feet of seaward shoreline advancement but offshore losses on the nearshore and offshore seafloor offset the beach gains for a modest net annual profile loss of yds 3 /ft of sand despite the additional project sand. Profile Brig-4: 4th Street North (Figures 4a & 4b) Brig-4 was established as part of the New Jersey Beach Profile Network in 1986, and included in the City's monitoring project in June The location is at the southern end of the engineered beach nourishment project area approximately 100 feet south of station No sand was placed in this region during the 2001 maintenance project but sand rapidly moved onto this beach immediately following construction. The initial Federal project placed yds 3 /ft of sand at this site. The fall 2011 ACOE maintenance project is scheduled to end just north of this location but the site will likely see some benefits from sand transferred south by littoral currents over the following months as sand erodes from the project beaches. Changes to this site over 2011 were modest with some wind blown sand accumulating on the foredune seaward slope and a small berm developing over the summer months raising the recreational beach elevation. Offshore sand movement was landward but it failed to reach the beach in large quantities this summer. The net change in sand volume for the year was a modest gain of yds 3 /ft of sand despite a small shoreline retreat of 12 feet largely caused by a steeper beachface slope from the development of the small berm. Provided enough sand remains in the system to the north sand should continue to feed south through this beach and maintain relative stability in this region. 7

10 Figure 4. The left photograph was taken November 18, 2010 following the winter with the worst storms in over a decade. The dunes on the left saw no damage from direct wave attack in spite of a low profile beach. The photograph on the right was taken on October 25, 2011 wind blown sand had accumulated near the dune toe. In the distance the leading edge of the ACOE project is visible seaward of the red roofed condo; the project is to be tapered into this region upon completion. Profile Brig-5: 5 th Street South (Figures 5a & 5b) This profile station was selected and established at 5 th Street South in December 1998 because the location was approximately midway between the end of the initial project beach at 4 th Street North and the established site at 15 th Street South. This site has a well-developed dune system composed of three significant ridges. The Federal project went south beyond this location placing just 8.11 yds 3 /ft. on the beach by March 3, No sand will be placed this far south during the current 2011 ACOE maintenance project. The dune system is expansive and continues to grow seaward with sand blown from the wide open beach towards the dune toe adding additional volume and width to the dunes annually. Over the summer sand pushed higher onto the beach to establish a modest beach berm but the steeper beachface slope resulted in a net shoreline retreat for the year of 15 feet. On both the nearshore and offshore seafloor sand was lost offsetting any gain on the beach with a net volume loss of yds 3 /ft of sand for the year. This site over the years has demonstrated a transitional trend between a zone of erosion to the north and accumulation on the southern beaches as sand moves south through this region on littoral currents. Figure 5. The photo on the left taken November 18, 2010 shows an outstanding dune system present at this location but with a cut path at a lower elevation used to access the beach. This beach continues to accumulate sand from the Federal project to the north and has developed into a wide, stable shoreline with abundant dune protection. By October 25, 2011 additional sand blown across the wide beach has accumulated on the seaward slope extending the dune toe seaward about 15 feet. 8

11 Profile Brig-15: 15th Street South (Figures 6a & 6b) At 15 th Street South, the dune is absent as the near continuous dune system is interrupted by the Ramada Vacation Suites (old Brigantine Hotel, built in 1929) that abuts against the exposed wooden bulkhead between 14 th and 15 th Street South. North of 14 th Street South and south of 15 th Street South the bulkhead is buried below a well-developed dune system. Over the year the upper beach gained sand blown landward across the beach and raising the beach elevation by about 1 foot. The berm crest location remained relatively consistent throughout the year but the shoreline position varied. Initially the shoreline advanced 80 feet by May 2011 but then gave back about half that gain over the summer for a net shoreline advance of 44 feet by October 25, Once again both the offshore and nearshore seafloor lost sand that offset the onshore gains that resulted in a modest net sand volume loss for the year at this site of yds 3 /ft of sand. This site is located at a nodule point for the City beaches both from a geographical location and sand deposition and erosion perspective. Figure 6. The picture from November 2010 (left) shows the width of the beach seaward of the Ramada Suites in the region were dune growth has been restricted at 15 th Street South. In contrast in the distance the dune is well established and provides substantial storm protection for those oceanfront properties and public infrastructure landward of the feature. By October 25, 2011 the beach elevation is higher and the shoreline advanced seaward burying the tip of the exposed rock groin barely visible in the November 2010 photo in the upper right corner of the photo. Profile Brig-27: 27th Street South (Figures 7a & 7b) This site was established in 1992 for the city s beach monitoring program. The location was selected to fill a void between two preexisting sites, located at 15 th Street South and 43 rd Street south. In contrast to 15 th Street South, Brig-27 has a well-established dune system. The three ridges act as multiple barriers to storm wave damage. The dune continued to expand seaward in 2011 with aeolian deposition along the seaward slope. The upper beach was relatively stable while the berm crest and shoreline advanced seaward. On the nearshore sand accumulated raising the seafloor elevation by 4 feet resulting in 53 feet of shoreline advance. Further offshore the seafloor remained relatively stable. The large wedge of sand that moved onto the nearshore likely derived from beaches to the north then carried south on littoral currents increased the net site volume at this site by yds 3 /ft. of sand. This region has been accumulating sand nearly continuously since monitoring began in 1992 and accelerated after the initial beach nourishment efforts put more sand into the littoral system. Extension of the Absecon Inlet jetty has created a region of backfill that continues to extend north past this site. The jetty will continue to trap sand moving south transported by longshore currents towards the inlet providing a source of sand to feed this dune system and beach s expansion seaward for the foreseeable future. 9

12 Figure 7. The left-hand photograph was taken in November 2010 and shows the expansive dune development over the last several decades from the 15 th Street South Ramada Suites in the distance and this site. There is little threat from typical storm wave damages along the Brigantine City oceanfront from south of the Ramada Vacation Suites building to the Absecon Inlet jetty. The picture to the right taken on October 25, 2011 shows the continued natural seaward expansion of the dune system with dune grass and other early colonizing plants spreading out onto the upper beach. From here to the inlet jetty, the vegetated dune system has continually grown wider since monitoring began in 1992 to the point now where it is a 700-foot hike from the 43 rd Street South street-end to the open beach. Profile Brig-43: 43rd Street South (Figures 8a & 8b) This site was established in 1986 as part of the New Jersey Beach Profile Network and was incorporated in the City's monitoring project in June The profile is located in the area dominated by the sand retention characteristics of the Absecon Inlet jetty. Sand collects all along this beach segment from the Absecon Inlet jetty to about 15 th Street South ever widening the southern section of beach. In 1986 the end of the street was the start of the beach with little dune growth. Today the reference position lies 640 feet landward of a huge dune system that extends to the shoreline position (zero datum) in The present shoreline here is almost a half mile seaward of the shoreline position before the inlet jetty was built in The dune system occupies nearly 800 feet of width between the development and the toe of the big primary dune. Smaller dunes now trap sand 250 feet landward of the beach berm crest and the shoreline lies 1,400 feet from the original starting point of the survey. Figure 8. The picture on the left was taken from a low dune ridge forming about 250 feet landward of the current berm crest. The vast sand plain making up this beach between the jetty and the Ramada Vacation Suites in the distance in each picture makes it clear that sand deposited along the island of Brigantine makes its way south to the Absecon Inlet jetty. This section of the City of Brigantine is a monument to the Absecon Inlet jetty s ability to trap sand. By October 25, 2011 the low dune ridge that developed in 2010 was over washed and completely flattened likely the result of storm 10

13 surge and wave run-up from Hurricane Irene as it made landfall just north of Brigantine. Overtime a new foredune ridge will inevitably form again on this expansive beach. Despite last winters stormy weather ( ) this beach still managed to accumulate sand for an annual beach volume gain of yds 3 /ft of sand and a 39-foot shoreline advance for This trend continued again in 2011 with another yds 3 /ft of sand added to the beach and 59 feet of seaward advance in the shoreline position. The net gain over just the last two years was yds3/ft of sand with a shoreline advance of 98 feet. Sustainable growth at this site year after year makes it an ideal location to consider sand harvesting to reuse and redistribute some of this sand back to the northern erosional zone. The process of recycling sand would reduce the cost substantially of repetitive maintenance projects designed to bring new sand to the region from either mainland quarry sites by truck or hydraulically mined and pumped by dredges from the inlet shoals and offshore borrow zones. Profile Brig-1: South Beach (Figure 9a & 9b) Located just 600 feet from the jetty, the site was established to determine if sand simply stopped at the jetty or fluctuated between deposition and erosion as material moved around the end of the rock structure. After several years of observations, the latter response appears to be the way things work. In spring 2009 a cycle of erosion took the berm back to the toe of the dune near the jetty preventing vehicular parking and significant recreational use of the beach at high tide. The pattern reversed with sand moving back to the beach by May In 2011 sand continued to move onshore, establishing a modest dry recreational beach berm that extended about a 100 feet seaward of the dune toe. Landward cross shore sediment transport resulted in sand from the nearshore and offshore seafloor moving to the beach in Swell from Hurricane Irene likely helped move the sand from nearshore and deeper offshore towards the beach. Despite some gains from this process on the beach most of the material was swept into the inlet or away from the site significantly offsetting the gains onshore. The resulting net annual change for 2011 was 59 feet of shoreline retreat and a net loss of yds 3 /ft of sand. A majority of this loss occurred in the second half of the year while the first half of the year the beach was relatively stable. The new berm beachface was steeper than the relatively flat intertidal shelf that was present at the end of 2010 resulting in the shoreline retreat, despite the increased recreational berm width. Figure 9. The left picture taken in November 2010 shows the 4WD entrance to this popular surfing and recreational beach buggy accessible beach. The huge, wide beach north of this site is devoted to swimming and pedestrian traffic only. The photo taken on October 25, 2011 right shows an elevated berm and typical vehicle use for this season on a weekday. Summer weekend use is over 2 orders of magnitude greater number of vehicles parked in just the view showing. The 3 becomes Absecon Inlet Jetty Erosion Study On August 25 th, 2011 the Coastal Research Center (CRC) completed the beach erosion assessment at the Absecon Inlet Jetty. A complete survey of the Brigantine shoreline adjacent to Absecon Inlet was conducted by the CRC field crew to document current conditions along the inlet shoreline. The survey 11

14 data were analyzed in ArcGIS software to generate a digital elevation model (DEM) of the area. A shoreline position change analysis was performed to determine shoreline migration rates from 1995 to Digital Elevation Model The survey data were analyzed in ArcGIS software where a continuous, 3-dimensional digital elevation model (DEM) surface was generated by interpolating the RTK GPS (real time kinematic global position system) elevation data between multiple survey lines (Figure 10). The DEM is color coded with the cooler blue colors representing lower elevations and warmer red colors representing higher elevations. Contour lines were created at two foot increments for additional visualization of elevation change throughout the area of study. All elevation units are in US survey feet and are referenced to the North American Vertical Datum 1988 (NAVD88) survey datum. The inlet shoreline has a lobe of sand which extends eastward. This will eventually migrate eastward and form a beach in the inlet at the base of the jetty. Much of the inlet beach surveyed is low lying and not much higher than 4ft NAVD88. The ocean facing beach has a moderately sized beach face giving way to a gradual downward slope. Figure 10, Cooler blue colors represent lower elevations, and warmer red colors represent higher elevations. Contour intervals are 2-ft. Elevation units are in the NAVD88 datum. Much of the inlet beach surveyed is low lying and not much higher than 4ft NAVD88. The ocean facing beach has a moderately sized beach face that slopes gradually seaward. 12

15 Shoreline Migration Shoreline migration of Brigantine s beaches in the vicinity of Absecon Inlet where analyzed from 1995 to 2011 using shorelines positions from: 1995, 2002, 2006, 2007, 2010 and The net shoreline movement (NSM) of inlet facing and ocean facing shorelines were quantified separately to identify potentially different trends. The individual beach movements among these shorelines from 1995 to 2011, were determined in ArcGIS using the Digital Shoreline Analysis System extension (DSAS). The 1995, 2002, 2006, 2007, and 2010 shorelines were delineated from aerial photography. The 2011 shoreline was obtained from survey data collected by the CRC. The shorelines are depicted on aerial photographs taken in 2010 (figure 12). Most recently, November 25, 2011, a private pilot provided the photograph below of the inlet shoreline. Figure 11. Photograph of the Brigantine Absecon Inlet shoreline November 25, Note that the finger of sand surveyed in August (see Figure 10 above) now extends further seaward as an exposed bar at low tide. This should promote further deposition and trapping of sand moving south around the jetty from the ocean beach. The beach and inlet shoreline positions experienced similar trends but to different degrees (figure 13). Both the inlet and ocean facing shorelines advanced, 66 ft and128 ft respectively, from 1995 to The most significant fluctuation in shoreline position occurred during the next time period, between the 2002 and 2006 when a quick and dramatic retreat of the inlet shoreline was seen. The retreat in shoreline position during this time is due to the close proximity of the borrow zone used to dredge sand for the 2003/2004 Atlantic City beach replenishment project. From 2002 to 2006 both the inlet and ocean facing shorelines saw a retreat, but the inlet shoreline retreated at a far more dramatic rate of ft while the beach front shorelines retreated only -19 ft. Though the inlet shoreline position started to advance in 2007 it has not yet reached its position seen in Since 1995 the inlet shoreline has retreated -606 ft. The beach front shoreline has remained seaward of its 1995 position advancing 69 ft, but it is not quite at the peak seen in

16 Figure 12, Shoreline migration of Brigantine s beaches in the vicinity of Absecon Inlet where analyzed from 1995 to 2011 using shorelines positions from 1995, 2002, 2006, 2007, 2010 and Shoreline positions are overlain on 2010 aerial photography. The most significant fluctuation in shoreline position occurred between 2001 and 2006 when a quick and dramatic retreat of the inlet shoreline was seen. Inlet Study Summary The current survey of the Absecon Inlet area conducted by the CRC shows a low lying beach between the inlet channel and the jetty. Since 1995 the inlet facing beach in Absecon Inlet has experienced significant erosion while the ocean facing beach has slightly advanced. The removal of sand from Borrow Zone C located near the inlet shoreline had the effect of generating a 600,000 cubic yard hole 26 feet deep just 400 feet from the jetty. Tidal currents acted to sweep all the sand in the immediate vicinity into this hole to fill it, producing the rapid loss of the inlet shoreline beaches with retreat along the jetty reaching a maximum in the 2007 photography. The Inlet shoreline position has not recovered from the retreat seen from 2002 to 2006, but sand has begun to accumulate on the inlet beaches advancing the shoreline over the past 3-4 years. With the current trend the inlet beaches are expected to return to their pre-borrow zone dredging positions in the future, barring the additional removal of sand from the inlet system. The 2011 maintenance fill of Absecon Island by the Army Corps did not take any sand from between the inlet jetties, instead borrowing from the ebb-tidal shoals seaward of the inlet system. Future surveys of the Absecon Inlet beaches would provide current shorelines as well as determine volumes of sand lost or gained throughout the survey area. It is recommended the Inlet beaches be surveyed annually to verify the current trend of the advancing shoreline. 14

17 Figure 13, the cumulative shoreline positions of the inlet and ocean facing beaches are depicted. Since 1995 the inlet shoreline retreated 580 feet by 2006 and recovered 260 feet since The oceanfront shoreline has remained seaward of its 1995 position advancing 69ft, but it is not quite at the peak seen in Report Conclusion: After effects from the El Nino winter of 2009 to 2010 that resulted in continued loss from both the feeder beach north of the promenade at the north end of Brigantine Boulevard and exposure of the rock revetment and loss of the dry beach along the promenade, the Philadelphia District US Army Corps of Engineers (ACOE) initiated a beach maintenance project to repair damages to this section of beach. The maintenance project brought sand from a mainland quarry hauled to the beach by trucks then spread by bulldozers to restore a dry recreational beach seaward of the promenade. Restoration efforts were limited to repairing damage caused by the storms and not with restoring the beach to the initial federal project design template. As a result the dry recreational beach constructed provides only temporary shore protection by burying the revetment rocks and preventing severe erosion that occurs when the waves reflect from the rocks and scour the beach. The current project provides adequate protection against accelerated erosion but without a significant increase in sand deposited on the feeder beach the new material will not remain in place for very long. At some point in the near future the ACOE will need to do a maintenance effort to restore both the promenade beach and the feeder beach to the original design parameters to provide some stability to the region s shoreline. Following the return of the beach to the design size, then sand harvesting and transfer from the southern beaches should be considered as a means to slow erosion and significantly extend the interval between major nourishment cycles. The southern shoreline continues to expand seaward annually from the littoral transfer of new sand south from the project beaches. Harvesting some of this sand deposit to reuse at the north end makes the Brigantine shoreline more sustainable with a reduction in maintenance costs, enhanced stability of the north end beaches and a reduction of the use of offshore and inlet borrow sites to provide additional sand to Brigantine s shoreline. The 15

18 ACOE continues to study the effectiveness of beach harvesting and truck hauling sand back to an area of erosion from the zone of accretion. An independent pilot study was done in 2006 by the Borough of Avalon where 20-cubic yard, 4wd-drive trucks hauled 58,000 cubic yards of sand back to 21 st Street from a zone 1.5 miles south. The cost was less than a third of buying the sand from a quarry and with the expense of setting up the equipment to hydraulically dredge sand (mobilization), far cheaper than bringing in a dredge every 3 years. Since last year s report the City of North Wildwood is preparing to define a zone of surplus sand along their municipal shoreline to utilize as source material for an area of chronic deficiency. In addition they are reaching out to their island neighbors the City of Wildwood and Wildwood Crest both recipients of excess sand derived from North Wildwood. Harvesting this excess sand would benefit both communities who have experienced the burial of municipal storm water drains related to the accumulation of sand and provide North Wildwood with an alternative sand source to traditional beach nourishment. Brigantine has the ability to do the same with its own abundance of excess sand deposited along the southern shoreline. This year the City of Brigantine Beach gained 228,007 cubic yards of sand that amounts to an additional 9.08 yds 3 /ft. for every foot of Brigantine s 25,097 feet of shoreline including the majority of the northern Green Acres tract. However, the majority of the gain was concentrated between 15 th Street South and the Absecon Inlet Jetty where 285,104 cubic yards accumulated. Losses towards the middle of the island from 15 th Street South to 5 th Street South and on the feeder beach and promenade region partially offset these gains. From the north end project beach from the feeder beach south to 4 th Street North has lost an annual average of approximately 95,000 cubic yards of sand. While the southern shoreline from 27 th Street South to just north of the Absecon Inlet Jetty has averaged an annual net gain of 131,500 cubic yards of sand. Looking at data from between 2006 and 2010 it is increasingly clear that sand harvesting can help sustain the chronic erosional region and reduce the need for expensive and repetitive beach nourishment projects by recycling sand back into the system. Southerly littoral currents will continue to transport sand from north to south along the Brigantine Beach shoreline chronically enhancing the beaches in the south at the expense of the northern oceanfront. 16

19 30 City of Brigantine to 2010 Comparison rd BRIG Street South (NJBPN #131) Elevation, Feet (NAVD 88) Line Survey Date Oct Nov Figure 19 - To emphasize the dramatic increase in sand supply at the southern end of Brigantine Island, the very first Coastal Center cross section was plotted rd against the most recent for 43 Street South. The shoreline has advanced 3 by 493 feet and the sand volume has increased by yds /ft. Just 10% of this quantity between 43rd and 27th Streets would provide (4132 x 29.2 cy/ft.) = 120,654 cubic yards of sand for recycling to the north Distance, Feet Figure 14. The 43 rd Street South cross section was established at the end of the pavement on the street end over 400 feet west of where this plot starts. The main dune ridge at the 600-foot mark did not exist in 1986, but dunes were established landward of the 400-foot mark. The zero elevation shoreline position advanced slowly over the decades to the point where enough sand has been added to permit; the practicality, sustainability, relative ease, and low cost with which a hundred thousand cubic yards of sand could be annually moved back to the 12 th Street North area in the City of Brigantine. 17

20 Shoreline Trends at 27th Street South Brigantine, NJ (Brig-27) The 2001 Beach Fill Added 600,000 cy at the North End of the City Shoreline Gains Have Been Cyclic with Periods of Loss. The Net is + 93 Feet Feet from Reference Position Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Year Q Annual Shoreline Position Shoreline Position Trend Poly. (Shoreline Position Trend) Figure 15. Trend in the zero elevation shoreline for 27 th Street South profile site since the first quarter of The quarterly surveys ended in 2006 with work resuming in 2008 on a semi-annual basis. The last four years of data are compressed at the right side of both of these figures. The 27 th Street site has shown relative stability following a loss cycle in late The 9-year trend is positive by 93 feet of shoreline advance seaward. 18

21 Shoreline Trends at 43rd Street South Brigantine, NJ (Brig-43) 450 Feet from Reference Position Sand Arrives More Slowly at 43rd St. and Cycles of Loss Still Occur. Note that 2 Years Elapsed with No Data Collected 2006 to 2008 Resulting in a Big Advance that Continued Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Year Q Annual Shoreline Position Shoreline Position Trend Poly. (Shoreline Position Trend) Figure 16. Trend in the zero elevation position for 43 rd Street since the first quarter of There are cycles of gain and loss here as well, with the past four years showing a large up-swing in sand accretion since Q-4 of Figure 10 covers this same site in cross section since 1986 showing nearly a 500-foot advance in the 0.0 ft. NAVD88 elevation shoreline location. 19