Vulnerability to Hurricane Damage on the U.S. Gulf Coast Since 1950

Abstract

We study hurricane risk on the U.S. Gulf Coast during 1950‐2005, estimating the wind damage and storm surge from every hurricane in this extended period. Wind damage is estimated from the known path and wind speeds of individual storms and calibrated to fit actual damage reports for a sample of Gulf Coast storms. Storm surge is estimated using the model developed by . These models provide the first comprehensive overview of the hurricane storm hazard as it has been experienced over a fifty‐six‐year period. We link the estimated damage with information on the population and specific socio‐demographic components of the population (by age, race, and poverty status). Results show that white, young adult, and nonpoor populations have shifted over time away from zones with higher risk of wind damage, while more vulnerable population groups–the elderly, African Americans, and poor—have moved in the opposite direction. All groups have moved away from areas with high risk of storm surge since 1970. But in this case, perhaps because living near the water is still perceived as an amenity, those at highest risk are whites, elderly, and nonpoor households. Here exposure represents a trade‐off between the risk and the amenity.

Key words:

• disaster
• vulnerability
• resilience
• risk assessment

Notes

1. Code for running HURRECON is available at: http://harvardforest.fas.harvard.edu:8080/exist/xquery/data.xq?id=hf025. As described in Emery Boose and others (2001, 32‐33):“The sustained wind velocity (V_s) at any point P in the northern hemisphere is estimated as $V_s=F[V_{\mathrm{m}}-S(1-sinT)V_h/2]\times {[{(R_{\mathrm{m}}/R)}^{B}exp(1-{(R_{\mathrm{m}}/R)}^B)]}^{1/2}$where F is a scaling parameter for effects of friction (water = 1.0, land = 0.8), V_m is the maximum sustained wind velocity over water anywhere in the hurricane, Sis a scaling parameter for asymmetry due to forward motion of the storm (1.0), T is the clockwise angle between forward path of the hurricane and a radial line from the hurricane center to point P, V_h is the forward velocity of the hurricane, R_m is the radius of maximum winds (50–100 km), R is the radial distance from the hurricane center to point P, and B is a scaling parameter controlling shape of wind profile curve (1.3). The peak wind gust velocity (V_g) at point P is estimated from V_s as follows: $V_{\mathrm{g}}=GV{\mathrm{g}}_{\mathrm{s}}$where G is a gust factor (water 5 1.2, land 5 1.5). The maximum 1/4 mile wind velocity (V_f) is estimated from V_s and G using Fujita's method (Fujita 1971: Eq. 12). Wind direction (D) at point P is estimated as $D=A_z-90-I$where A_z is the azimuth from point P to the hurricane center and I is the cross isobar inflow angle (water 5 208, land 5 408). In the southern hemisphere, where the wind circulation is clockwise around the center, T is the counterclockwise angle between forward path of hurricane and a radial line from hurricane center to point P, and D = A_z + 90 + I.”

2. In a series of publications Emery Boose and others (1994, 2001, 2004) have described a modification of the original Fujita scale that is used in their HURRECON model. This is the scale that we employ here. In addition, there is now an “enhanced Fujita scale” that is recommended for studies of tornados but not for hurricanes (Womble and others 2009).

3. A list of the forty‐three hurricanes and a map of the estimated extent of wind damage and storm surge in each event is provided here: http://www.s4.brown.edu/hurricane/HurricaneMaps.html.