This study assesses the feasibility of a beach and dune system as flood defense against storm surge along the coastlines of the Houston-Galveston area, proposed as a part of the Coastal Texas Project. We apply a semiempirical analytical model to predict dune erosion in a dual-dune system under changing climate conditions. Synthetic storms were simulated using validated hydrodynamic, wave, and hurricane models to produce input data (storm surge, wave height, and period) for the dune erosion model, reflecting both present day and future climate scenarios that incorporate projected sea level rise (SLR). Bias-correction techniques were applied to climate model output using historical observations of storm surge and wave data. An alternative sampling approach was also developed to stochastically predict dune erosion by integrating synthetic data into a copula-based framework. Results indicate that the annual-average dune erosion is approximately 8%-10% of system volume in the present scenario and increases to 33%-40% in future scenarios with higher SLR, leading to estimated dune rehabilitation cycles of 8-10 and 2-2.5 years, respectively. These findings suggest that, although the proposed beach and dune system is likely to be effective for storm surge protection under the present climate condition, significant adjustments will be desirable to maintain its resilience in the face of evolving climate and sea level rise. Importantly, bias correction of input data yielded substantial reductions in predicted storm surge and significant wave height, resulting in more accurate dune erosion predictions. This demonstrates the necessity of bias correction of hydrodynamic and wave parameters derived from global climate simulations for reliable coastal risk assessment and future planning. The copula sampling approach produced results comparable to the original results, which considered storms with extremely low or high occurrence probabilities, while providing lower sensitivity to bias-correction methods and copula generator types.

The Ike Dike is a concept of coastal barrier system designed to protect the Houston-Galveston area (HGA), which is highly susceptible to flood risks from storm surges. The barrier system has been proposed with different alignments and configurations: movable, permanent, and extended permanent barrier systems. We have evaluated and compared the feasibility of three barrier types as a function of sea level rise (SLR), taking into account the reliability of the movable barrier. We employ the Delft3D Flexible Mesh suite to simulate storm surges in a hydrodynamic model, incorporating pressure and wind velocity fields spatialized by the Holland’s model from synthetic storm tracks. Simulations are driven by a range of SLR projections and synthetic storm tracks, with different barrier types. Probabilistic flood depths are predicted for specific return periods by fitting the 30-year maxima flood depths from the simulations to a probability distribution function. Using the CoreLogic database of residential properties in the HGA and building damage functions, we calculate probabilistic flood damages for each predicted flood depth. This allowed us to quantify flood risk as the expected annual damage, integrated over a range of return periods. Our results indicate that the permanent and extended permanent barrier systems are more effective at mitigating storm surge risk than the movable barrier system. Moreover, the necessity of the extended permanent barrier system becomes more significant as SLR increases.

Hurricane Ike, which struck the United States in September 2008, was the ninth most expensive hurricane in terms of damages. It caused nearly USD 30 billion in damage after making landfall on the Bolivar Peninsula, Texas. We used the Delft3d-FM/SWAN hydrodynamic and spectral wave model to simulate the storm surge inundation around Galveston Bay during Hurricane Ike. Damage curves were established through the relationship between eight hydrodynamic parameters (water depth, flow velocity, unit discharge, flow momentum flux, significant wave height, wave energy flux, total water depth (flow depth plus wave height), and total (flow plus wave) force) simulated by the model and National Flood Insurance Program (NFIP) insurance damage data. The NFIP insurance database contains a large amount of building damage data, building stories, and elevation, as well as other information from the Ike event. We found that the damage curves are sensitive to the model grid resolution, building elevation, and the number of stories. We also found that the resulting damage functions are steeper than those developed for residential structures in many other locations.