New Jersey: Coastal Flood Inundation Mapping
The U.S. Geological Survey (USGS) in cooperation with the New Jersey Department of Environmental Protection and New Jersey Office of Emergency Management conducted a study to produce flood-inundation maps for storm surge flooding scenarios in the coastal areas of 10 New Jersey counties. The coastal storm-surge inundation maps were created from data modelled in the FEMA Region II Coastal Storm-Surge study. The flood-inundation maps show areas of potential coastal flooding from wind driven storm surge for two different simulated coastal storms. The flood-inundation maps are displayed in the common datum of NAVD88 and linked to 25 USGS tide gages along the coast of New Jersey. Users can access real-time tidal elevation data from the USGS New Jersey Tide Network webpage and will be able to display flood-inundation maps for a range of tidal elevations to better understand areas of potential flooding. The study also investigated the magnitude of inundation on building structures and major roads at moderate flood level for communities within the mapped station extents.
Digital flood-inundation maps for an approximately 295-mile length of the New Jersey coastline and tidewaters through 10 coastal counties stretching from Cumberland County through Bergen County were created by the U.S Geological Survey (USGS) in cooperation with the New Jersey Department of Environmental Protection (NJDEP) and New Jersey Office of Emergency Management (NJOEM). The flood-inundation maps depict extent and depth estimates of coastal flooding corresponding to selected tidal elevations recorded by 25 real-time USGS tide gages located throughout the length of the study area coastline. The flood-inundation maps can be accessed through the U.S Geological Survey Flood Decision Support Toolbox (FDST) Web site.
For this study, previously published modelled data was utilized from the coupled ADvanced CIRCulation hydrodynamic model for Oceanic and Estuarine Waters (ADCIRC) and Simulating Waves Nearshore (SWAN) model from the FEMA Region II study. Six synthetic modelled tropical storm events were selected based on parameters including landfall location or closest approach location, maximum wind speed, central pressure, and radii of winds. Two storm events were selected per tide gage providing two “scenarios” and accompanying inundation-map libraries for each gage. Flood-inundation maps reflect between nine to thirty stages (elevations) at each tide gage that correspond to areal extents and depths for ADCIRC-SWAN storm time steps extracted from modeled hydrographs at the gage locations. Water surface elevations from ADCIRC-SWAN node points extending through each tide gage extent were used to interpolate a water surface. Combining these surfaces with a geographic information system (GIS) topobathymetric digital elevation model (TBDEM) from the USGS Coastal National Elevation Database (CoNED) Applications Project (Danielson and others, 2018) delineated the area flooded by coastal waters at each tide gage elevation.
The availability of these maps to visualize potential inundation for selected water levels along with real-time water level data available online from USGS tide gages, coastal impact statements, and forecasted tide elevations from the National Weather Service (NWS), will provide emergency management personnel and residents with a link between numeric and text warning information and images of estimated inundation extents in their community. User selected display of inundation allows early response activities to NWS forecasted water level elevations or mitigation planning by selecting targeted water levels and planning critical pre-flood activities such as building elevations, early traffic pattern changes because of neighborhood building inundation levels, improved understanding about when major road access is affected, as well as for post-flood recovery efforts.
A subsequent analysis of several community metrics including total structures, structure density, percent of buildings inundated, and roads/bridges affected by flooding were used to evaluate moderate flooding impacts among the mapped station extents. Initial comparisons are presented to show the variability of these characteristics within each mapped station extent then extended to evaluate impacts from moderate flooding on these same areas. The analysis used simulated inundation layers at moderate flood stage to investigate the magnitude of inundation on building structures and major roads among the mapped station extents. The community analysis of impacts at moderate flooding based on these inundation scenario maps should provide community leaders and local and state planning officials with tools to better visualize and understand how flooding begins to disrupt and damage building structures and major roads as a surrogate for direct increased risk to human life and property.
New Jersey Tide Network
The U.S. Geological Survey (USGS) in cooperation with the New Jersey Department of Environmental Protection and New Jersey Office of Emergency Management conducted a study to produce flood-inundation maps for storm surge flooding scenarios in the coastal areas of 10 New Jersey counties. The coastal storm-surge inundation maps were created from data modelled in the FEMA Region II Coastal Storm-Surge study. The flood-inundation maps show areas of potential coastal flooding from wind driven storm surge for two different simulated coastal storms. The flood-inundation maps are displayed in the common datum of NAVD88 and linked to 25 USGS tide gages along the coast of New Jersey. Users can access real-time tidal elevation data from the USGS New Jersey Tide Network webpage and will be able to display flood-inundation maps for a range of tidal elevations to better understand areas of potential flooding. The study also investigated the magnitude of inundation on building structures and major roads at moderate flood level for communities within the mapped station extents.
Digital flood-inundation maps for an approximately 295-mile length of the New Jersey coastline and tidewaters through 10 coastal counties stretching from Cumberland County through Bergen County were created by the U.S Geological Survey (USGS) in cooperation with the New Jersey Department of Environmental Protection (NJDEP) and New Jersey Office of Emergency Management (NJOEM). The flood-inundation maps depict extent and depth estimates of coastal flooding corresponding to selected tidal elevations recorded by 25 real-time USGS tide gages located throughout the length of the study area coastline. The flood-inundation maps can be accessed through the U.S Geological Survey Flood Decision Support Toolbox (FDST) Web site.
For this study, previously published modelled data was utilized from the coupled ADvanced CIRCulation hydrodynamic model for Oceanic and Estuarine Waters (ADCIRC) and Simulating Waves Nearshore (SWAN) model from the FEMA Region II study. Six synthetic modelled tropical storm events were selected based on parameters including landfall location or closest approach location, maximum wind speed, central pressure, and radii of winds. Two storm events were selected per tide gage providing two “scenarios” and accompanying inundation-map libraries for each gage. Flood-inundation maps reflect between nine to thirty stages (elevations) at each tide gage that correspond to areal extents and depths for ADCIRC-SWAN storm time steps extracted from modeled hydrographs at the gage locations. Water surface elevations from ADCIRC-SWAN node points extending through each tide gage extent were used to interpolate a water surface. Combining these surfaces with a geographic information system (GIS) topobathymetric digital elevation model (TBDEM) from the USGS Coastal National Elevation Database (CoNED) Applications Project (Danielson and others, 2018) delineated the area flooded by coastal waters at each tide gage elevation.
The availability of these maps to visualize potential inundation for selected water levels along with real-time water level data available online from USGS tide gages, coastal impact statements, and forecasted tide elevations from the National Weather Service (NWS), will provide emergency management personnel and residents with a link between numeric and text warning information and images of estimated inundation extents in their community. User selected display of inundation allows early response activities to NWS forecasted water level elevations or mitigation planning by selecting targeted water levels and planning critical pre-flood activities such as building elevations, early traffic pattern changes because of neighborhood building inundation levels, improved understanding about when major road access is affected, as well as for post-flood recovery efforts.
A subsequent analysis of several community metrics including total structures, structure density, percent of buildings inundated, and roads/bridges affected by flooding were used to evaluate moderate flooding impacts among the mapped station extents. Initial comparisons are presented to show the variability of these characteristics within each mapped station extent then extended to evaluate impacts from moderate flooding on these same areas. The analysis used simulated inundation layers at moderate flood stage to investigate the magnitude of inundation on building structures and major roads among the mapped station extents. The community analysis of impacts at moderate flooding based on these inundation scenario maps should provide community leaders and local and state planning officials with tools to better visualize and understand how flooding begins to disrupt and damage building structures and major roads as a surrogate for direct increased risk to human life and property.