Role of wetlands in reducing structural loss is highly dependent on characteristics of storms and local wetland and structure conditions

Abstract

Coastal communities in New Jersey (NJ), New York (NY), and Connecticut (CT) sustained huge structural loss during Sandy in 2012. We present a comprehensive science-based study to assess the role of coastal wetlands in buffering surge and wave in the tri-state by considering Sandy, a hypothetical Black Swan (BS) storm, and the 1% annual chance flood and wave event. Model simulations were conducted with and without existing coastal wetlands, using a dynamically coupled surge-wave model with two types of coastal wetlands. Simulated surge and wave for Sandy were verified with data at numerous stations. Structural loss estimated using real property data and latest damage functions agreed well with loss payout data. Results show that, on zip-code scale, the relative structural loss varies significantly with the percent wetland cover, the at-risk structural value, and the average wave crest height. Reduction in structural loss by coastal wetlands was low in Sandy, modest in the BS storm, and significant in the 1% annual chance flood and wave event. NJ wetlands helped to avoid 8%, 26%, 52% loss during Sandy, BS storm, and 1% event, respectively. This regression model can be used for wetland restoration planning to further reduce structural loss in coastal communities.

A sensitivity study of rising compound coastal inundation over large flood plains in a changing climate

“…Therefore, future study should use a three-dimensional vegetation-resolving surge-wave model, e.g., CH3D-SWAN 13 – 15 , coupled to a watershed model, with extensive vegetation data (type, distribution, height, stem density, leaf area index, stem size, rigidity, inland migration, etc.) to produce more accurate flood maps and to quantify the value of coastal wetlands in reducing coastal flooding damage in the region 8 , 60 to enhance coastal resiliency and wetland restoration.…”

“…Although we did not compare the TCs and coastal inundation based on all CMIP5 and CMIP6 climate models and downscaling models, this study suggests that downscaling with KE model (e.g., GFDL-ESM4-KE) and high-resolution RCM (e.g., FSUGSM-WRF) can improve the prediction of TCs by global climate models. NASHM 38 predicted TCs were successfully used to calculate the 1% flood in New Jersey and New York 8 . Both KE and NASHM can generate hundreds or more TCs for SWFL to enable more robust results.…”

“…Coastal flood vulnerability has increased worldwide due to gradually accelerating sea-level rise (SLR) 1 – 4 , intensifying and wetter tropical cyclones (TCs) 5 , 6 driven by climate change and increasing coastal development. Coastal communities have incurred dramatically increasing TC-induced flood damages 7 , which are highly dependent on the local conditions of the flood, wave, infrastructure, SLR, landscape, and their interactions 8 . While 40% of the world population lives in the coastal region within 100 km of the coastline, 10% of the population lives within the low elevation coastal zone (LECZ) less than 10 m above the sea-level 9 .…”

Coastal marshes provide valuable protection for coastal communities from storm-induced wave, flood, and structural loss in a changing climate

“…Communities not only would like to know the value of coastal wetlands for flood protection in the current climate, they would also like to know the impact of climate change (e.g., sea level rise) as well as wetland management action on the value of coastal wetlands. Sheng et al 6,7 , hereafter referredto as SHE21a and SHE21b, used extensive data and comprehensive dynamic and regression models to estimate the value of coastal wetlands for flood protection in NJ and New…”

“…During Superstorm Sandy, coastal wetlands along New Jersey (NJ), New York (NY), and Connecticut (CT) coasts (Fig. 1a) provided a modest reduction of structural loss in coastal communities 1,3,6 due to the relatively sparse and low Spartina marsh and the high storm tide. On the other hand, Sheng et al 7 found that the tall and dense Phragmites-dominated Piermont Marsh buffered the Village of Piermont, located 40 km north (upstream) of New York City (NYC) on the Hudson River, from massive structural loss during Sandy.…”