The limited role salt marshes may have in buffering extreme storm surge events: Case study on the New Jersey shore

Abstract

The hybrid hurricane and storm event dubbed “SuperStorm Sandy” of October 2012 was the most costly natural disaster to hit the US Atlantic coast, and the second most costly to affect the United States. This extreme weather event presented an excellent opportunity to assess the effectiveness of tidal salt marshes and maritime forests in buffering adjacent development from storm-related damage. To address this question of how well did or under what conditions did coastal ecosystems buffer adjacent human development, we undertook to quantify the incremental monetary value that a hectare or linear extent of fronting salt marsh and/or maritime forest had on protecting the built environment of the back-bay communities in the Barnegat Bay region of New Jersey, USA. Statistical modeling was used to estimate the relationship between the spatial extent and characteristics of fronting coastal wetlands with the various damage metrics derived from the Federal Emergency Management Agency National Flood Insurance Program payout and Preliminary Property Modeling Task Force damage data at the scale of the individual housing unit. While salt marshes may be effective in diminishing wave energies and buffering adjacent development under normal conditions, in the case of SuperStorm Sandy, we find no evidence that New Jersey's extensive coastal marshes significantly buffered and thereby reduced NFIP payouts on the majority of back-bay residential properties. The extreme conditions of this storm event with storm surges upwards of 2 m, effectively flooded these marshes diminishing their protective capacity. The bulk of the residential properties damaged in our study area were located in lagoonal communities that are built directly adjacent to tidal water and are thereby highly vulnerable to storm surge-related flooding whether or not they are buffered by adjacent marshes. The results of this study should not be misconstrued in concluding that salt marshes do not have a positive value in protecting coastal properties; rather, their protective buffering capacity for extreme storm events is limited and that lagoonal-style developments remain highly vulnerable to sea level rise and future storms.