Hurricane-driven storm surge flooding could cause billions in damage to residential structures along the U.S. gulf and Atlantic coasts in 2011, according to the “2011 CoreLogic Storm Surge Report.”
CoreLogic developed the report to enhance understanding of the heightened risk storm surge waves pose to homes in areas prone to tropical storms. The report complements the Federal Emergency Management Agency (FEMA) flood zone information to provide a complete picture of potential property damage exposure. Many properties outside designated flood zones are still at risk for storm surge damage.
Storm surge is triggered primarily by the high winds and low pressure associated with hurricanes, which cause water to amass inside storms as they move across the ocean and release as powerful rushes over land when hurricanes move on shore. In addition to the property damage and lives lost to flooding, the speed and force associated with storm surge waves can increase significantly geographic and economic impact in hurricane disaster areas. The data helps insurance providers and financial services companies understand the potential damage exposure for homes that do not fall into designated flood zones and, therefore, likely do not carry flood insurance but remain at risk of storm surge.
“The local flood zones defined by FEMA in high-risk coastal regions provide a great deal of exposure data for homes in the path of flood waters, but understanding the additional layer of risk posed by a storm surge is critical for homeowners, emergency response teams, insurance companies and many others to plan and prepare for natural catastrophes,” said Howard Botts, executive vice president and director of database development for CoreLogic Spatial Solutions. “As the report shows, in many cases homes exposed to potential storm surge inundation are located outside of designated flood zones, and those homeowners need to be aware of their vulnerability to severe damage and property losses.”
CoreLogic generated the report using the company’s comprehensive parcel database. After identifying the top 10 high-risk urban areas based on the probability of a hurricane’s striking, vulnerability to storm surge given onshore and offshore geographic attributes and population density, CoreLogic identified all residential properties within a predicted storm surge area and analyzed it against the associated property value of each home. The analysis divided property valuations first by hurricane category, then within each region by ZIP code. The final results show the current value of all residential properties exposed to potential storm surge damage and allow for the comparison of properties at risk for storm surge damage to those properties also within a FEMA flood zone. Cities examined in the analysis include New Orleans; Mobile, Ala.; Charleston, S.C.; Corpus Christi, Houston and Galveston, Texas; Jacksonville, Tampa and Miami-Dade, Fla.; Virginia Beach, Va.; and Long Island, N.Y.
Of the metro areas studied in the report, Long Island was found to have the highest exposure to risk, valued at $99 billion, followed by the Miami-Palm Beach region and Virginia Beach. Projected exposure to storm surge damage for the 10 geographies is as follows:
- Long Island: $99 billion
- Miami-Dade: $44.9 billion
- Virginia Beach: $44.6 billion
- New Orleans: $39 billion
- Tampa: $27 billion
- Houston: $20 billion
- Jacksonville: $19.6 billion
- Charleston: $17.7 billion
- Corpus Christi: $4.7 billion
- Mobile: $3 billion
Other key findings include percent of homes in flood and surge zones and total individual properties at risk in each geographic region. The report indicates the majority of homes at risk for storm surge damage within the 10 metro areas are outside FEMA-defined flood zones.
For example, 87.4 percent of surge-inundation zone properties are not in a flood zone in Virginia Beach. Only 12.2 percent of at-risk homes are in surge and flood zones. Among the densely populated coastal regions with the highest number of individual properties exposed to storm surge damage are: Virginia Beach with nearly 289,000 properties; New Orleans with more than 278,000 properties; and Tampa with more than 277,000 homes at risk.
The report also points out the effects of man-made mitigation efforts in the New Orleans metro area. According to the report, reconstruction efforts during the past six years, which included raising area levees, rebuilding flood walls and creating the massive Lake Borgne Surge Barrier, provide greater protection from storm surge destruction. Many homes previously designated in a high-risk surge zone now have a significantly lower chance of exposure to property damage.
“The important thing to remember is that though individual homeowners can greatly reduce hurricane wind damage with improvements to buildings and structural design, they are often powerless to mitigate the impact of storm surge and resulting saltwater flooding,” Botts said. “It’s a common misconception for homeowners to think that if they live outside of a FEMA flood zone they are safe from hurricane-driven storm surge flooding, when in reality their property is vulnerable to the most destructive natural flooding catastrophes that can occur alongside a tropical storm.”