PROJECT STATEMENT
Houston- Galveston Region is home to one of the largest petrochemical complexes in the world, located at low elevation vulnerable to storm surge. NOAA predicts that sea levels will increase and storm surge will become more severe along the Texas coast. In the Gulf Coast, sea level projects to rise up to 6.2feet and maximum envelop of high water will be 28.2 feet by 2100. Multiple Lines of Defense Structure is a resilient system for protecting low-lying neighborhood from flooding and the eventual impacts of sea level rise. It relies on nature-based measures adapting to sea level rise by natural accretion of mineral and biogenic sediments, restoring ecosystem destroyed by historic hurricanes and secure the long-term sustainability of coastal protection. Consequently, within this system, there is a framework to link people with the shoreline and with the water through engagement, and the expansion of a water-based recreational economy.
PROJECT NARRATIVE
BACKGROUND & PROBLEM STATEMENT
The long-term prospect of catastrophic sea-level rise in Houston-Galveston Region is the inevitable effect of climate change. NOAA predicts that the mean sea level will rise up to 6.2feet by 2100, and Sea level rise has had a significant impact on coastal ecosystems resulting in increased coastal inundation, high-risk storm surge and increases in the duration and frequency of flooding from storm surge. For example, in 2008, Hurricane Ike wreaked havoc on Texas, causing 113 deaths and almost $30 billion in damage. Galveston Bay and Houston Ship Channel in Houston- Galveston Region are home to one of the largest petrochemical complexes in the world, serving an important role in the regional, state and even national economy. But this low-lying coastal region is particularly vulnerable to storm surge exacerbated by sea level rise. The objective of this project is to design a sustainable system with layered strategies adapting to sea level rise, which can mitigate storm surge, restore ecosystem and connect people with water through engagement and recreation, expanding water-based ecological and economic benefits.
REGIONAL CONDITIONS
Flooding and hurricanes are major concerns along the Gulf Coast. The frequency of a normal hurricane along any 50-mile segment of the Texas coast is one about every 6 years, and the annual average occurrence of a tropical storm or hurricane is 0.8. Houston-Galveston Area will be significantly inundated by storm surge from hurricanes from Category 3 and above. Relatedly, sea level rise will increase the vulnerability of coastal communities to hazards such as flooding and hurricanes. By 2100, more than 6% of Houston to be covered by storm surge resulting from Category 5 Hurricane. Historically, Houston-Galveston Area has experienced three severe storm surges. In response to different hurricanes which caused huge damage for coastal cities, protection was built to save these cities. In 1904, 17-foot seawall was built at the east end of Galveston Island because of Hurricane Galveston in 1900 with 15-foot storm surge, and today it is approximately 10 miles. In 1982, 20-foot levee system was built to protect 2400-acre areas of Texas City, induced by Hurricane Caria belonging to Category 5 Hurricane. But existing protection was insufficient to protect the region, especially during the Hurricane IKE in 2008 which was only Category 2 Hurricane but caused 16-foot storm surge.
MULTIPLE LINES OF DEFENSE STRUCTURES
Echoing to different reasons for coastal flooding, this design develops and incorporates a series of adaptable flood attenuation measures, referred to as the Multiple Lines of Defense Structure with fourfold protections.
Line I— The living breakwaters are sited in the gulf to absorb wave energy and create slow moving water, which can save lives, reduce damage to structures, and reduce floodwater elevations. Calm water in turn encourages sedimentation, which replenishes protective beaches. This growing ecological dissipation differs from traditional structures because of establishment of oyster reefs on the top adapting to climate change and sea level rise.
Line II— Super levee can resist to overflow efficiently. When it is overtopped, the flowing water does not breach the levee because it flows slowly across its top surface. Super levee will be proposed in conjunction with a special urban development along the ocean.
Line III— The restoration of oyster reef in the Galveston Bay allows for improved water clarification and water quality and recovering from overharvesting of oyster, provides habitat for vertebrates and invertebrates, as well as mitigating storm surge in the bay. We want to reduce risk while increasing our perception of risk by building interventions that integrates aquatic habitat and community access, therefore, surrounding communities are encouraged to participate in this activity, motivating education and recreation in the bay.
Line IV— The restoration of wetland along the ship channel provides opportunities to connect this design with the Greens Bayou planed and conducted by Houston government. Such green and blue ways are of great help to relief the environmental pressure from industry and mitigate flooding problem. The design is to be implemented in three phases:
Phase 1) Dissipation— focus on building living breakwater and installing wave attenuator in the gulf to dissipate wave energy. The first phase aims to control the storm surge at source. Cooperation between wave attenuator and breakwaters is designed to reduce nearly 70% of wave height. Breakwaters are designed as living system biogenically in parallel with future sea level rise which will enhance maritime ecosystems and link risk reduction with a renewed stewardship of a biodiversity and activated shoreline.
Phase 2) Restoration and Adaptation— restore oyster habitats and introduce salt marsh in bay, and establish wetland along ship channel. And all living systems adapt to sea level rise.
The design incorporates oyster restoration as one of the breakwaters designs. All of living structures keep up with sea level rise by natural accretion of mineral and biogenic sediments and achieve the goal to reduce 80% of wave height. The restoration and establishment of wetlands provides an opportunity to connect the Multiple Lines of Defense Structure with Greens Bayou.
Phase 3) Protection and Recreation– built super levee to save people living in Galveston Island and Bolivar Peninsular from inundation caused by worst sea level rise by 2100. Simultaneously, Formation of recreational islands in the gulf and bay can reduce wave height by up to 85% as well as well as providing opportunity for education research and development of tourism.
