Geographic Focus: Texas|Louisiana|Mississippi|Alabama|United States East Coast
NOAA Office for Coastal Management
A tool that supports users undertaking a community-based approach to assessing coastal hazard risks and vulnerabilities by providing maps that show people, places, and natural resources exposed to coastal flooding. This product is based on knowledge and experiences the Office for Coastal Management has in community-based risk and vulnerability assessments. Users should read the FAQ available on the website to understand the data behind the mapper. The flood data used in the mapper are a combination of FEMA Digital Flood Insurance Rate Maps and Q3 flood data available as of June 2014.
Geographic Focus: Nassau County, NY|Queens County, NY|Kings County, NY
Orton, Philip, Talke, Stefan A., Jay, David A., Yin, L., Blumberg, Alan, Georgas, Nickitas, Zhao, Haihong, Roberts, Hugh J., MacManus, Kytt
Here, we demonstrate that reductions in the depth of inlets or estuary channels can be used to reduce or prevent coastal flooding. A validated hydrodynamic model of Jamaica Bay, New York City (NYC), is used to test nature-based adaptation measures in ameliorating flooding for NYC's two largest historical coastal flood events. In addition to control runs with modern bathymetry, three altered landscape scenarios are tested: (1) increasing the area of wetlands to their 1879 footprint and bathymetry, but leaving deep shipping channels unaltered; (2) shallowing all areas deeper than 2 m in the bay to be 2 m below Mean Low Water; (3) shallowing only the narrowest part of the inlet to the bay. These three scenarios are deliberately extreme and designed to evaluate the leverage each approach exerts on water levels. They result in peak water level reductions of 0.3%, 15%, and 6.8% for Hurricane Sandy, and 2.4%, 46% and 30% for the Category-3 hurricane of 1821, respectively (bay-wide averages). These results suggest that shallowing can provide greater flood protection than wetland restoration, and it is particularly effective at reducing "fast-pulse" storm surges that rise and fall quickly over several hours, like that of the 1821 storm. Nonetheless, the goal of flood mitigation must be weighed against economic, navigation, and ecological needs, and practical concerns such as the availability of sediment.
Data Product, Dataset, Decision Support, Map Viewer
Geographic Focus: Guam|United States Virgin Islands|United States of America|Puerto Rico
NOAA Office for Coastal Management
A mapping tool that gives users the capability to visualize potential impacts from sea level rise, focusing on the continental United States, Hawaii, Puerto Rico and U.S. Virgin Islands, Guam, and Saipan. A slider bar is used to show how various levels of sea level rise will impact coastal communities. The viewer features display of potential future sea levels, simulations of sea level rise at local landmarks, communication of the spatial uncertainty of mapped sea level, model results of potential marsh migration due to sea level rise, overlays of social and economic data onto potential sea level rise, and an examination of how tidal flooding will become more frequent with sea level rise. Data are available for download. Users should read the "Frequently Asked Questions about the Tool" in the "Additional Information" section for information about data sources, data update frequency, and the modeling approach.
Rising sea levels are increasing the exposure of populations and infrastructure to coastal flooding. While earlier studies estimate magnitudes of future exposure or project rates of sea level rise, here, we estimate growth rates of exposure, likely to be a key factor in how effectively coastal communities can adapt. These rates may not correlate well with sea level rise rates due to varying patterns of topography and development. We integrate exposure assessments based on LiDAR elevation data with extreme flood event distributions and sea level rise projections to compute the expected annual exposure of population, housing, roads, and property value in 327 medium-to-large coastal municipalities circumscribing the contiguous USA, and identify those localities that could experience rapid exposure growth sometime this century. We define a rate threshold of 0.25% additive increase in expected annual exposure per year, based on its rarity of present-day exceedance. With unchecked carbon emissions under Representative Concentration Pathway (RCP) 8.5, the number of cities exceeding the threshold reaches 33 (18–59, 90% CI) by 2050 and 90 (22–196) by 2100, including the cities of Boston and Miami. Sharp cuts under RCP 2.6 limit the end-of-century total to 28 (12–105), versus a baseline of 7 cities in 2000. The methods and results presented here offer a new way to illustrate the consequences of different emission scenarios or mitigation efforts, and locally assess the urgency of coastal adaptation measures.
Buchanan, Maya K., Kopp, Robert E., Oppenheimer, Michael, Tebaldi, Claudia
Estimates of future flood hazards made under the assumption of stationary mean sea level are biased low due to sea-level rise (SLR). However, adjustments to flood return levels made assuming fixed increases of sea level are also inadequate when applied to sea level that is rising over time at an uncertain rate. SLR allowances—the height adjustment from historic flood levels that maintain under uncertainty the annual expected probability of flooding—are typically estimated independently of individual decision-makers’ preferences, such as time horizon, risk tolerance, and confidence in SLR projections. We provide a framework of SLR allowances that employs complete probability distributions of local SLR and a range of user-defined flood risk management preferences. Given non-stationary and uncertain sea-level rise, these metrics provide estimates of flood protection heights and offsets for different planning horizons in coastal areas. We illustrate the calculation of various allowance types for a set of long-duration tide gauges along U.S. coastlines.
Geographic Focus: Ocean County, NJ|Monmouth County, NJ
Wong-Parodi, Gabrielle, Fischhoff, Baruch, Strauss, Benjamin H.
The risk of coastal flooding is increasing due to more frequent intense storm events, rising sea levels, and more people living in flood-prone areas. Although private adaptation measures can reduce damage and risk, most people living in risk-prone areas take only a fraction of those measures voluntarily. Here, we examine relationships among individuals’ beliefs and actions regarding flood-related risks, based on in-depth interviews and structured surveys in communities deeply affected by Superstorm Sandy. We find that residents recognize the risk of coastal flooding and expect it to increase, although they appear to underestimate by how much. Although interview participants typically cited climate change as affecting the risks that they face, survey respondents’ beliefs about climate change are unrelated to their willingness to tolerate coastal flooding risks, their beliefs about the effectiveness of community-level mitigation measures, or their willingness to take individual actions. Respondents who reported greater social support also reported both greater tolerance for flood risks and greater confidence in community adaptation measures, suggesting an important, but complex role of personal connections in collective resilience – both keeping people in place and helping them to survive there. Thus, residents were aware of the risks and willing to undertake both personal and community actions, if convinced of their effectiveness, regardless of their beliefs about climate change.
The Federal Emergency Management Agency (FEMA) recently completed a coastal demographics study of the United States and U.S. territories. As part of this study, FEMA estimated the United States population subject to the 1% annual chance (100 y) coastal flood hazard as mapped by FEMA. This determination followed a three-step process: (1) create a national digital flood hazard database by compiling the best available coastal-proximate, digital flood-hazard-area data using FEMA data sets; (2) develop a systematic method to separate coastal and riverine flood hazard areas and incorporate this boundary into the digital flood hazard database; and (3) combine the year 2000 census data with the digital flood hazard database using a geographic information system. This enabled estimates of the U.S. population subject to the 1% annual chance coastal flood. The analysis was conducted at the census block-group level, with census block-group populations (permanent residents) assumed to be uniformly distributed across each block group. The results demonstrate that approximately 3.0% of the U.S. population lives in areas subject to the 1% annual chance coastal flood hazard. It must be emphasized, however, that these numbers are based on the 1% annual chance (100 y) coastal flood. Historical coastal floods less frequent than the 1% chance annual flood have occurred in the U.S. on numerous occasions. If less-frequent coastal flood events were considered in this study, such as the 0.2% annual chance (500 y) coastal flood or, if seasonal (vacations) population were considered, then a much greater percentage of the U.S. population would be determined as subject to coastal flooding.
Colle, Brian A, Buonaiuto, Frank, Bowman, Malcolm J, Wilson, Robert E, Flood, Roger, Hunter, Robert, Mintz, Alexander, Hill, Douglas
New York City, New York (NYC), is extremely vulnerable to coastal flooding; thus, verification and improvements in storm surge models are needed in order to protect both life and property. This paper highlights the Stony Brook Storm Surge (SBSS) modeling system. It utilizes surface winds and sea level pressures from the fifth-generation Pennsylvania State University (PSU)–National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5) or the Weather Research and Forecasting (WRF) model to drive the Advanced Circulation Model for Coastal Ocean Hydrodynamics (ADCIRC). For this study, the MM5 is utilized at 12-km grid spacing and ADCIRC is run on an unstructured grid down to ∼10-m resolution in areas around Long Island and NYC. This paper describes the SBSS and its performance across the NYC region during the 11–12 December 1992 nor'easter and Tropical Storm Floyd on 16–17 September 1999. During the 1992 event, east-northeasterly surface winds of 15–25 m s−1 (30–50 kts) persisted for nearly 24 h, while hurricane-force winds (35–40 m s−1) occurred for a few hours just south of western Long Island. This created a 1.0–1.5-m storm surge around NYC and western Long Island Sound over three tidal cycles. ADCIRC successfully simulated the peak water levels to within ∼10%, and it realistically simulated some of the flooding across lower Manhattan. The surface winds for Tropical Storm Floyd were only 5–10 m s−1 weaker than the 1992 event, but no coastal flooding occurred during Floyd, because the storm approached during a low tide. Additional Floyd simulations were completed by shifting the storm's landfall to the spring high tide the previous week, and by doubling the wind speed to mimic a category-1 hurricane. A combination of the spring high tide and a category-1 hurricane scenario during Floyd would have resulted in moderate flooding at several locations around NYC.