Objectives

Our project goal is to quantify the potential impact of sea level rise and hurricane intensification on hurricane-induced economic damages and on population dynamics at the coast; we will pursue the following four objectives:

1. To develop a general, parameterized response model for hurricane flood elevation and wave damage potential as a function of SLR and hurricane intensification.
2. To determine potential acceleration in hurricane flood elevation and wave height probability as a function of SLR and hurricane intensification.
3. To determine potential acceleration in hurricane-induced economic damages and population affected at the coast due to accelerating flood elevation and wave height probability.
4. To determine potential short and long-term shifts in population dynamics at local and regional levels as well as the socioeconomic dimensions of such shifts.

Methodology

The scientific merit of our proposal lies in 1) the development of parameterized response models for the coupled effect of SLR and hurricane intensification on hurricane flooding and hurricane waves; and 2) the linkage of these response models to project socioeconomic consequences, namely acceleration in economic damages and in future shifts in race and income demographics at the coast. The following outlines our proposed methodology.

1. Develop Future Climate Scenarios. To project future hurricane flooding and waves, both SLR and sea surface temperature (SST) rise will be projected based on the future climate scenarios of the Intergovernmental Panel on Climate Change (IPCC; 2007) and reported subsidence rates. Higher potential SLR rates reported since IPCC report publication will also be considered. We will assume an 8% intensification in hurricane central pressure per 1oC of SST rise (Knutsen and Tuleya 2008). With this assumption, future hurricane scenarios will represent future hurricane possibilities, should a tropical system develop into a major hurricane.
2. Develop Parameterized Flood Elevation and Wave Response Models. Accurate numerical modeling of hurricane surge and waves to determine probability of flooding and economic damage has traditionally required the use of high-resolution numerical grids and a large suite of hurricane scenarios along tracks spaced at least every 25 km along the coast. Furthermore, each coupled hydrodynamic-wave simulation is time intensive (3,000 computational hours per storm). The use of surge response functions (SRF), which parameterize the surge response with respect to hurricane meteorological conditions, can reduce numerical simulation requirements for extreme-value flood elevation statistical analysis by 75% without loss of accuracy (Irish et al. 2009). We propose to:
   1. Extend the SRF methodology to include SLR, wave setup, and flow contributions due to storm-induced erosion of barrier islands, where analysis will be performed using ADCIRC, SWAN, and XBEACH; and
   2. Apply a similar methodology to predict wave conditions (height, period, direction) at the coast to assess wave damage potential (wave response model, WRF). The WRF development, using SWAN, will consider additional wave growth due to hurricane intensification and change in waves at the coast due to SLR.
3. Project Future Hurricane Flood Elevation and Wave Probability. Potential increase in flood and wave probability will be determined using a joint-probability approach (Resio et al. in press) where the SRFs and WRFs will be coupled with meteorological probability. Analysis of the historical Gulf of Mexico hurricane record will be used to determine present-day conditional probability functions for hurricane landfall, central pressure, and size, among other factors. By relaxing the statistical stationary assumption, potential hurricane intensification and SLR will be incorporated to create a time-varying meteorological-climatological probability function.
4. Project Population Affected and Economic Damages. Geographic information system (GIS) applications will be developed to identify flooded areas, evaluate population impacted, and estimate the economic damages associated with future probabilistic hurricane conditions (e.g. 25-yr and 50-yr return periods) to quantify acceleration in hurricane hazard. Economic damages will be estimated, based on flood depth and wave condition, and contrasted with insurance claims when available. A GoogleEarth tool will be developed to visualize results.
5. Project Population Dynamics. The socioeconomic impacts of SLR and increasing hurricane damage probability (e.g., 25-yr and 50-yr return periods) will be assessed using GIS and statistical tools. These tools will be employed to ascertain the effects of sea level rise on the basis of projected land use and population demographics as currently predicted in comprehensive plans at state, regional, and local levels (to the extent available). The following sources of data will inform this study: census data at the local and regional levels, community population projections, current and future land use maps, and sales and property tax data. Potential impacts on social capital will be studied qualitatively through plan review and informant interviews with local and state officials.

Rationale

Our proposal addresses the Natural Hazard and Climate Change Resiliency priorities 1, 2, and 4, “to increase public understanding of risks associated with coastal hazards and [SLR]”, to “develop new… planning tools… to increase resiliency to coastal hazards and [SLR],” and to “predict socioeconomic impacts of climate and sea level change on population dynamics.” Because of their potential to generate massive surges and waves, hurricanes pose a significant threat to coastal communities on the Gulf of Mexico. However, the potential implications of global warming, namely SLR and hurricane intensification, on hurricane inundation, damages, and community behavior are not well understood. Research on the coupled effect of SLR and intensification of extratropical wind events suggests an increase in future economic damages. While research on the impact of global warming on hurricane damages has considered SLR, the implication of future intensification of major hurricanes on flooding has only recently received attention. Prior hurricane studies to assess global warming impacts also neglected the potential significant impact of wave setup (water level rise due to wave breaking), wave destructive potential, and the additional flooding in bay communities resulting from barrier island overwash and breaching in low-lying coastal areas. Preliminary research by the Texas A&M PIs, which accounted for waves and barrier island breaching, suggests that for Corpus Christi, TX, damage to homes and businesses impacted by flooding due to a major hurricane could rise more than 250% by the 2080s due to coupled SLR and hurricane intensification. Potential users include local, state, and federal planning and policymakers to include the TX General Land Office, the Mississippi Coastal Civil Defense, Florida Department of Community Affairs, the U.S. Army Corps of Engineers, and the Federal Emergency Management Agency.