Development of a coastal sand dune management program

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Coastal sand dunes can provide protection from flooding and wave action to coastal development. Generally, the volume of sand contained in a dune above the storm surge level and its elevation determine whether the dune will survive a given storm and continue to provide protection. The elevation of the dune crest and its alongshore continuity will determine whether the dune provides protection from coastal flooding. Thus, dunes are desirable coastal features from a shore protection standpoint. However, dunes also have their detractors. High dunes can obstruct a coastal property owner or tenant’s view of the ocean, one of the many reasons people visit the shore. Unstabilized dunes can also cause problems with wind-blown sand. Dunes stabilized with vegetation can mitigate the wind-blown sand problem, but maintenance of the vegetation requires that pedestrian traffic over the dunes be precluded. Thus, bathers must often walk some distance to a dune crossover structure in order to reach the beach. To address these conflicting uses and to satisfy state regulators, a sand dune management program was developed for the City of Ocean City, New Jersey in 1986. During the period covered by the dune study, a number of small beach nourishment projects were undertaken by the State of New Jersey and the City of Ocean City; however, the program pre-dated the major beach nourishment program undertaken by the U.S. Army Corps of Engineers in the early 1990s. At the time of the dune study (1986), Ocean City’s beaches were relatively narrow and, in some areas, did not supply enough sand for dunes to exist and grow. In other areas dunes existed but were periodically eroded during storms. In these areas, the sand supply on the beach seaward of the dunes was sufficient to allow the dunes to recover. Development of the dune management program involved the collection of beach profile data in the vicinity of the existing dunes and to characterize the conditions under which dunes could exist and survive in Ocean City. A typical dune profile, characteristic of Ocean City, was developed and areas where dunes could be developed and maintained identified. Shoreline change trends were quantified for the 8-mile-long beach using 21 sets of historical aerial photographs taken over the 32-year period from 1952 to 1984. The location of the seaward dune 1 Samuel S. Baxter Professor, Department of Civil, Architectural & Environmental Engineering, Drexel University, Philadelphia, PA 19104. 2 Assistant Professor, Department of Civil Engineering, University of North Carolina at Charlotte, Charlotte, NC 28223-0001. vegetation line was defined at 41 locations and plotted as a function of time. In general, beaches toward the south end of the barrier island were accreting, those near the middle of the island were retreating and those near the north end were variable but, in the long term, stable. The deviation of the vegetation line’s position from the 32-year trend line was plotted against the “day of the year” on which the measurement was made in order to extract any seasonal effect. This attempt to quantify the seasonal variation of the seaward dune vegetation line was not successful. The final dune management program included a dune profile “typical” of Ocean City and the locations along the beach where those dunes could exist and be maintained. (The subsequent Corps of Engineers’ major beach nourishment project allows this dune profile to exist along all of the nourished shoreline.) Sand that accumulates to raise the dune crest elevation above +15 feet NGVD datum can be removed provided that it is placed in front of the existing dune; thus, the dune maintains its volume of sand per unit length of beach. A 20-foot wide easement behind the dune and in front of the existing bulkhead/sea wall was established to allow pedestrian traffic behind the dune and to allow construction vehicles access to the back of the dune. The study was incorporated into the City of Ocean City’s dune ordinance

Visibility over shorefront sand dunes: an ocean view

Retrieved 3/15/2006 from http://www.pages.drexel.edu/~weggel/DuneVisibilityWeb.pdf.Discusses how designers of protective coastal dunes can compromise between construction/design considerations and aesthetic considerations

Rainfalls of 12 July 2004 in New Jersey

Retrieved 3/15/2006 from http://www.pages.drexel.edu/~weggel/Rainfalls%20of%2012%20July%202004%20in%20New%20Jersey.pdf.The recent rainfalls in southern New Jersey appear to have broken all records. Rainfall at Tabernacle, NJ was reported at 11 inches. If this much rainfall fell during a 24-hour period, it would be the 5,000-year event for the southern New Jersey - Philadelphia area. That is, on average – over many millennia – this much rainfall could be expected to occur once in 5,000 years. A better way to express it is that it would have a probability of 1/5000 = .0002 or a 0.000002% chance of occurring in any one year. The graph below shows the return period of rainfalls for various durations ranging from ½ hour to 24 hours. For example, the 100-year, 24-hour rainfall for the Philadelphia area is about 7 inches. If those 7 inches fell in only 12 hours, it would be a 250-year rainfall; if it fell in 3 hours, it would exceed the 1,000-year rainfall. Thus, if the 11 inches at Tabernacle fell in less than 24 hours, say 12 hours, its return period would exceed the 10,000-year point rainfall. The data used to create the graph is from the Weather Bureau’s (now the National Weather Service) Technical Paper # 40, “Rainfall Frequency Atlas of the United States,” by David Hershfield, May 1961. Note that the lines have been extrapolated out quite far from the original data used to create the graph; hence, these return periods are very approximate!

Using a global positioning system to measure tidal currents in Absecon Inlet, Atlantic City, NJ

Journal of Surveying Engineering-Asce, 133(4): pp. 179-183.As a permit requirement for the development of a marina within Absecon Inlet, Atlantic City, NJ, tidal current measurements were required. Maximum ebb and flood currents determine the forces to which the structural elements of the marina will be subjected as well as sediment transport patterns near the marina. Currents also influence the maneuverability of small craft attempting to enter or exit the marina. Consequently, current velocities and directions during maximum ebb and flood tides (spring tides) were measured on 10 March 2005 in the vicinity of the proposed marina using the Global Positioning System (GPS). The location of the proposed marina in the inlet is shown in Figure 1. Current patterns are affected by the presence of Clam Creek (on southwest side of the study area) and the Route 87 Bridge over the inlet. The marina site is also subject to locally generated wind waves as well as waves entering the inlet from the Atlantic Ocean

Status of Muon Collider Research and Development and Future Plans

The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides continued work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (CoM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay ($\pi \to \mu \nu_{\mu}$) channel, muon cooling, acceleration, storage in a collider ring and the collider detector. We also present theoretical and experimental R & D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the R & D since the Feasibility Study of Muon Colliders presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A. Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics (Stanford Linear Accelerator Center, Menlo Park, CA, 1997)].Comment: 95 pages, 75 figures. Submitted to Physical Review Special Topics, Accelerators and Beam

Photographs of failed dams

Retrieved 3/16/2006 from http://www.pages.drexel.edu/~weggel/MedfordLakesPhotos.pdfPhotographs of dam failures and their aftermath at the Medford Lakes in New Jersey, July 12, 2004

Sediment Budget Calculations, Oceanside, California

Source: https://erdc-library.erdc.dren.mil/jspui/A sediment budget was constructed for the Oceanside, Ca1ifornia, area to predict the effect on adjacent beaches of each of two alternative solutions - groins and nearshore breakwaters-to the Oceanside erosion problem. The pre-project sediment budget was modified and assumptions made about the performance of each proposed project. The report discusses briefly each of the sources of data used budget, sets up the sediment balance equations, solves the equations in the under several sets of assumptions for conditions prevailing in the 1950-1972 time period, and then uses this pre-project sediment budget to evaluate the possible effects of the of the groin field and nearshore breakwater projects on adjacent beaches