The shoreline of Raritan Bay is developed with homes and recreation sites that are vulnerable to erosion and flooding exacerbated by increased rates of sea level rise. The US Army Corps of Engineers has implemented coastal storm-risk management projects or feasibility studies for several communities on Raritan Bay, but not all locations are included. Municipalities have some freedom in managing beaches and dunes, but scientific expertise is usually absent at local levels. The Rutgers Raritan River Consortium Minigrant Program provided the opportunity for Rutgers faculty and students to meet with decision-makers in Aberdeen Township, NJ, to devise a plan for protecting an eroding coastal segment at Cliffwood Beach (Figure 1). The multiple-disciplinary research team consists of Professor Karl Nordstrom, C2R2 graduate students Jonathan Miller and Tracy Youngster, and Professor John Dighton who acts as a technical advisor. The tasks for this team included: (1) gathering data on beach and dune characteristics and shoreline changes; (2) using the data and insight to make decisions about managing threatened coastal habitats and infrastructure; and (3) providing the quantitative data to support a future large-scale shore protection project funded by state or federal sources or use as a basis for a local project using municipal resources, and local arrangements for conducting field work. Local officials consulted included the mayor, town manager, head of the department of public works, and head of the environmental commission.
Cliffwood Beach Study Area. Photo from Google Earth 2016.
The shoreline of Raritan Bay is developed with homes and recreation sites that are vulnerable to erosion and flooding exacerbated by increased rates of sea level rise. The US Army Corps of Engineers has implemented coastal storm-risk management projects or feasibility studies for several communities on Raritan Bay, but not all locations are included. Municipalities have some freedom in managing beaches and dunes, but scientific expertise is usually absent at local levels. The Rutgers Raritan River Consortium Minigrant Program provided the opportunity for Rutgers faculty and students to meet with decision-makers in Aberdeen Township, NJ, to devise a plan for protecting an eroding coastal segment at Cliffwood Beach (Figure 1). The multiple-disciplinary research team consists of Professor Karl Nordstrom, C2R2 graduate students Jonathan Miller and Tracy Youngster, and Professor John Dighton who acts as a technical advisor. The tasks for this team included: (1) gathering data on beach and dune characteristics and shoreline changes; (2) using the data and insight to make decisions about managing threatened coastal habitats and infrastructure; and (3) providing the quantitative data to support a future large-scale shore protection project funded by state or federal sources or use as a basis for a local project using municipal resources, and local arrangements for conducting field work. Local officials consulted included the mayor, town manager, head of the department of public works, and head of the environmental commission.
Cliffwood Beach has become increasingly vulnerable to wave overwash and erosion, leaving the bayfront road and a well-used recreational beach, public park and parking lots at risk. The shoreline of interest (Figure 1) is bounded by a jetty at Whale Creek to the west and a seawall to the east. Ocean Boulevard and Veteran’s Memorial Park are the cultural features immediately threatened. Westerly longshore currents have delivered much of the beach sand to the vicinity of the jetty. The jetty has accumulated sand on the upper beach, but sand has bypassed the jetty lower on the beach and formed shoals at the mouth of Whale Creek. The Critical Zone near the bend in the road is sand-starved and narrow. The dunes that were there have eroded, leaving the road subject to wave undercutting and overwash. Structural damage to the road, park and parking areas will occur soon if no action is taken. Several protections strategies were evaluated, including installing a bulkhead or geotube (low cost bulkhead alternative), increasing the volume of the dune and stabilizing bare areas using vegetation planting, conducting a beach nourishment project using sand from external sources, and mechanical redistribution (backpassing) of the sand that has accumulated near the jetty.
PTK GPS topographic surveys were conducted every three months on 6 equally-spaced cross-shore transects along the beach depicted in Figure 1 to determine changes in dimensions and volumes of the beaches and dunes through time. Sediment samples were gathered to determine the appropriate grain size characteristics for a beach fill operation. Vegetation was sampled in the summer within 1×1 m2 quadrats placed continually across the dune in the six transects to provide data on species diversity and presence of invasive vegetation. Aerial photographs were used to provide the historical context and to supplement the field data for a calculation of the beach sediment budget.
Vegetation surveys revealed that, (1) plant diversity is high overall and increases from the Critical Zone (Figure 1) westward towards the jetty; (2) several species of native sand-stabilizing coastal grasses occur in the dune; (3) two of these species – bitter panicum (Panicum amarum) or Switchgrass (Panicum virgatum) could be used in barren areas in the dune to stabilize the sand and add habitat value; (4) Phragmites australis, an invasive, is encroaching on the dune near the western portion and should be monitored to determine if removal is necessary; and (5) keeping the beach unraked results in backshore plant communities not typically found on heavily managed municipal beaches. Topographic surveys reveal that dune widths varied from 15 m to 42 m with crest heights from 2.6m to 3.7m. Beach and dune volume calculations reveal that 17,480 m3 of sediment would be necessary to restore beach and dune characteristics in the critical zone to a condition that mimics portions of the dune just west of there that have provided sufficient protections against past storms. Approximately 700 m3 of sand per year would be required in a backpassing operation to match longshore losses in the critical zone and retain the calculated level of protection. The implication is that external funds would be required for the initial beach nourishment operation, while municipal equipment could be used in the backpassing operation that would make the project sustainable in the long term. Cost estimates for a geotube and bulkhead were provided in case these structures were selected as an alternative or backup to beach nourishment. The results of the projects were discussed with municipal authorities on 17 September 2018 to address feasibility of implementation.
The topographic and sediment data and analysis of shore protection options funded by the Rutgers Raritan River Consortium Minigrant have provided the documentation for the M.S. thesis of Jonathan Miller. Initial findings of the project were presented at the Annual Meeting of the Middle States Division of the American Association of Geographers on 26 October 2018.
For more information, contact: Karl F. Nordstrom, Ph.D. (nordstro@marine.rutgers.edu) or Jonathan C. Miller (jcmiller@marine.rutgers.edu).
Dr. Nordstrom presented a summary of his research at the November 8, 2018 Rutgers Raritan River Consortium breakfast meeting. Click on the link to view his presentation titled, Assessment of protection strategies for estuarine beaches: a case study of Cliffwood Beach, NJ.