Ike Dike costly but cheaper in long run
Study: Coastal spine could lessen impact of most hurricanes
As we continue into another hurricane season, coastal Texans are once again preparing to face storm surges — which is to say, the walls of ocean water that hurricanes push onto shore. Shortly after Hurricane Ike researchers at Texas A&M University at Galveston proposed a coastal spine, often referred to as the “Ike Dike.” Numerous surge models demonstrated that a coastal barrier would reduce the storm surge. The question, though, remained: Would that reduction be worth the hefty price tag?
As researchers at Texas A&M, Galveston, we set out to determine if such a large investment was cost effective. Our initial effort turned into a series of studies focused on the costs and benefits of a coastal barrier system running roughly from just west of San Luis Pass to just east of Rollover Pass. These studies evolved from relatively straightforward analyses of property damages to more sophisticated studies that included business disruptions and broader local, state and national economic effects.
We first investigated the effects of a coastal barrier on direct damages to residential structures for four different storms, ranging in intensity from a smaller, more likely hurricane (10 percent annual chance) to a lower probability, higher intensity storm (0.2 percent annual chance). This initial study revealed that depending on the size of the storm, residential structures worth between $6 billion and $16 billion are exposed to damaging storm surge in Harris, Galveston and Chambers Counties — an extraordinary number in and of itself.
The presence of a coastal barrier reduced damage from storm surge-based flooding by between 70 and 90 percent. These percentage figures represent between $423 million for a smaller, more likely hurricane, to $5.6 billion for a larger, less likely hurricane. For a storm that mimics the surge of Hurricane Ike, residential property damage was reduced from $2.9 billion to $135 million, a 95 percent loss avoidance.
Notably, these figures represent only residential losses. We expanded the study to include the economic impacts of storm
surge on petrochemical and industrial plants in the area. The addition of petrochemical and industrial plants adds structures worth between $8.7 billion and $17.5 billion that are exposed to storm surge. Further, because many plants on the coastline are forced to shut down because of the threat of a storm alone, irrespective of damage, additional indirect costs are incurred.
For the most conservative scenario of an 18-day shutdown, total losses range from $400 million for a likely hurricane, to $13 billion for a lower probability storm. These effects are significantly mitigated with a coastal barrier: a 100 percent reduction in total losses for smaller storms to a 76 percent reduction in larger, less likely storms.
Finally, economic effects of a storm surge are not isolated to the area flooded by the surge. Our local and regional economy is intricately linked to economies in other regions and states, and the ripple effect shows up in Texas’ and the nation’s gross domestic product, among other measures. For example, without coastal protection, a large lowprobability storm surge (a 500year event) could substantially slow the Texas economy’s longterm growth.
When considered over a 50year time frame, our projections show that without coastal protection, storm surges are likely to decrease Texas’ Gross State Product by 8 percent — which is to say, $863 billion. A coastal spine substantially mitigates these economic impacts. Further, all macroeconomic indicators — except for government expenditures — will also decline, with the value of net exports suffering the most profound decline by an estimated 13 percent, corresponding to $160 billion loss.
In summary, from the perspective of economic effectiveness, a coastal barrier system makes sense. To be clear, it is not a silver bullet to address the larger and increasingly challenging issues related to flooding in the region — there remains a substantial amount of long-term, comprehensive planning and implementation of many different flood mitigation techniques to address our larger flooding problems. A coastal barrier is, however, part of the larger solution to reduce regional flood risk and future economic impacts.
Davlasheridze is an assistant professor at Texas A&M University, Galveston Campus. Her research is focused on the economics of natural hazard impacts and mitigation. Wesley Highfield is an associate professor at Texas A&M University, Galveston Campus. His research is focused on the analysis and mitigation of natural hazards.