Storm Tide Amplification and Habitat Changes due to Urbanization of a Lagoonal Estuary

Abstract

Abstract. In recent centuries, human activities have greatly modified the geomorphology of coastal regions. However, studies of historical and possible future changes in coastal flood extremes typically ignore the influence of geomorphic change. Here, we quantify the influence of 20th Century manmade changes to Jamaica Bay, New York City, on present-day storm tides. We develop and validate a hydrodynamic model for the 1870s, based on detailed maps of bathymetry, seabed characteristics, topography, and tide observations, for use alongside a present-day model. Predominantly through dredging, landfill, and inlet stabilization, the average water depth of the bay increased from 1.7 to 4.5 m, tidal surface area decreased from 92 to 72 km2, and the inlet minimum cross-sectional area expanded from 4800 to 8900 m2. Total (freshwater plus salt) marsh habitat area has declined from 61 to 15 km2 and intertidal unvegetated habitat area from 17 to 4.6 km2. A probabilistic flood hazard assessment with simulations of 144 storm events reveals that the landscape changes caused an increase of 0.28 m (12 %) in the 100-year storm tide, even larger than the influence of global sea level rise of about 0.23 m since the 1870s. Specific anthropogenic changes to estuary depth, area and inlet depth and width are shown through targeted modeling and dynamics-based considerations to be the most important drivers of increasing storm tides.

Evolving tides aggravate nuisance flooding along the U.S. coastline

“…While insufficient historic and modern tide gauge data are available to assess trends in NF, the results presented for Wilmington and other estuaries suggest that the duration and frequency of NF have also likely increased here. Similarly, lagoonal or “back-bay” estuaries are not represented in the long NOAA (National Oceanic and Atmospheric Administration) tide gauge datasets, but large changes to tides have been shown to occur where inlets have been opened or closed ( 53 ) or have been deepened and widened ( 54 , 55 ). Long-term increases in tides have been observed for Jamaica Bay, New York City, for example, with a tide range in 1899 of 1.16 m increasing to 1.64 m in 2007 ( 55 ).…”

The Influence of Channel Deepening on Tides, River Discharge Effects, and Storm Surge

“…As shown by Familkhalili and Talke (2016), greater tide magnitudes can reduce or negate the effect of an amplified storm surge, if the storm peak is timed at low water. Therefore, an approach that considers a full range of different storm tracks, magnitudes, rainfall, and tides is likely needed, to fully assess changes to flood hazard caused by channel deepening (e.g., Orton et al., 2020).…”

Effect of Estuary Urbanization on Tidal Dynamics and High Tide Flooding in a Coastal Lagoon

“…Therefore, we also set Manning's-n in the deep channels to 0.02 s/m 1/3 . This value is a common choice (Garzon & Ferreira, 2016;Mattocks & Forbes, 2008) and the same as in prior research where the present-day model used here was validated for a simulation of the Hurricane Sandy (2012) storm tide (Orton et al, 2015(Orton et al, , 2020. Hence, there is no evidence for sub-grid scale changes in channel roughness over time due to dredging, unlike what is sometimes inferred in riverine systems (e.g., Helaire et al, 2019).…”

“…The modern NOAA (National Oceanic and Atmospheric Administration) record at Sandy Hook extends from 1911 to 1918 and from 1932 to the present. We recovered and digitized a historical (1877-1878), short (∼1 month) tidal data set at Holland House within Jamaica Bay (location shown in Figure 1), also from the U.S. National Archives (Orton et al, 2020). Holland House measurements were made by hand on tidal staffs at irregular 5 to 15-min intervals, with gaps during the night.…”

“…We improved the historical DEM (used by Orton et al (2020)) by using mapped ecological information to produce a more accurate representation of wetland and intertidal flats. Previously, the elevation in model grid cells with no bathymetric or topographic DEM data was estimated either through interpolation, if unvegetated, or assigned an assumed "high marsh" elevation.…”