Design in a Time of Uncertainty
By Rives Taylor, Principal, Global Resilience Research Lead
Nearly six years ago, on Sept. 13, 2008, Hurricane Ike made landfall at Galveston. With damage estimates totaling almost $30 billion, it now ranks as the third-costliest U.S. hurricane.
Ike’s major impacts in the Houston-Galveston area included widespread flooding in Galveston, catastrophic devastation on Bolivar Peninsula and the largest power outage in Texas history, which affected much of the metropolitan region.
Storm surge was a leading cause of Gulf-facing coastal destruction, with surge elevations estimated at 10 to 13 feet in Galveston and 13 to 17 feet on the Bolivar Peninsula, according to a survey by the Harris County Flood Control District.
Surging waters also accounted for widespread damage along the shoreline of Galveston Bay in Galveston and Harris Counties. Here’s an excerpt from a report by the National Weather Service:
Surge values of 10 to 13 feet were common along the Western Bay and Clear Lake. The communities of Shoreacres, Seabrook, Kemah and San Leon were especially hard hit by a combination of storm surge and wave action as evidenced by damage to structures, roads, piers and concrete riprap along the shoreline. Significant water was observed in the towns of Nassau Bay, Clear Lake Shores and Taylor Lake Village, due to high water entering structures from the surge getting into Clear Lake and Taylor Lake respectively. The gauge at Eagle Point near San Leon measured a maximum surge of 10.75 feet.
Ike’s damage to residential property in Harris County alone has been estimated at $8.2 billion, with a third of that cost caused by storm surge and associated wave action. A hurricane’s storm surge creates larger, stronger waves, resulting in sudden damage to shoreline structures.
A two-part research project
HARC is now engaged in a two-part research project to provide key information that will help policymakers make decisions about possible actions to reduce storm-surge damage in future hurricanes and tropical storms. The project is being led by Birnur Guven, a HARC research scientist in environmental modeling, and Jim Lester, HARC’s president and CEO.
One element of the research effort involves an evaluation of the now new, artificial islands Galveston Bay, serving as breakwaters, might mitigate the force of storm-magnified waves. The Islands that are envisioned by the researchers would feature sand and vegetation atop more resilient underwater structures. The resulting natural areas would add new wildlife habitat to the bay’s rich ecosystem.
The project’s second part is an opinion survey of people who live in coastal communities. Researchers want to find out which strategies these residents prefer to reduce the force of surge-boosted waves and storm-related flooding. Besides breakwater islands, different kinds of damage-reducing structures include jetties, levees, seawalls, flood gates and artificial reefs. Survey respondents are also being asked what they think of “non-structural” options, such as creating new wetlands to soak up floodwaters.
HARC has one basic goal in the project, Guven said: Collecting and analyzing information about flood-mitigation projects and about related public attitudes and then sharing those findings with public officials and other stakeholders who value public opinion.
The original concept for the project, which then centered mainly on a public opinion survey of flood-reducing options, was developed soon after Ike struck, but federal funding for the proposal was not obtained until 2012.
In the meantime, Guven said, some computer modeling was conducted to simulate and compare different options’ effectiveness. And the Flood Control District started considering breakwater islands as one possibility to alleviate some storm-surge impacts in future storms. A suggestion from that Harris County agency prompted a decision to expand the analysis to include modeling of such islands’ relative benefits.
HARC’s partners on the project includes researchers at Texas A&M University, the University of Texas and Texas A&M University-Galveston.
So far, initial modeling at Texas A&M has indicated that a plan for breakwater-island structures with shorter segments about a mile offshore seems to do the best job of reducing wave heights, Guven said.
Researchers at UT will now refine those findings with additional modeling that evaluates the different island widths and heights and incorporates more detailed storm data on storm surge and wave action.
Researchers at A&M-Galveston, meanwhile, have been working on the opinion survey – collecting, analyzing and summarizing data from detailed questionnaires.
The project schedule calls for HARC to produce a final report on both the modeling and opinion results by December. Meetings with county officials and other stakeholders will then be held to present the findings and solicit those individuals’ reactions to the different options.
The two largest and most prominent post-Ike proposals for structural flood-reducing projects in the Houston area are the Ike Dike, a barrier plan for the Gulf Coast that was developed at Texas A&M University-Galveston, and the Centennial Gate, a plan developed at Rice University that centers on a moveable flood gate across the Houston Ship Channel. The two proposals have some similar elements but also major differences, and there has been much public debate about their relative merits.
HARC’s study of breakwater islands and public opinion is “totally independent of the discussion about whether to build the Ike Dike or Centennial Gate,” Guven emphasized.
Nonetheless, the results of the HARC project’s opinion survey, which includes questions about different structures that are included in the Ike Dike and Centennial Gate proposals, may well factor into the continuing public dialog about them, she added.