A conceptual design of the Houston Ship Channel Barrier

The frequency of hurricanes along any 80 km segment of the Coast of Texas is about 1 in 6 years (Roth,2009). On average, 4 major hurricanes (category 3 or higher) occur every century in the Houston-Galveston Region (Needham and Keim, 2011). In addition, the region is very vulnerable: Houston is the fourth biggest city in the US, over 6 million residents live in the region; the Houston Ship Channel (HSC) accommodates the largest petrochemical complex in the US; and Galveston Bay provides large environmental value. Together, the population, industry and the environment make this region a very flood prone area. Action is required in the near future to protect Society, Economy and Environment. A number of solutions has already been proposed, by local parties and academic organizations, to protect both inside and outside Galveston Bay. Recent studies by the SSPEED Center (Sebastian et al. (2014), Bedient (2014) and Penland (2014)), however, conclude that with a closure of Galveston Bay, a significant residual surge can occur at the HSC entrance as a result of local wind set-up. This indicates the need of a structure inside the Bay, protecting the most valuable areas. The protection system is designed for a lifetime of 100 years. To elaborate on future growth of the infrastructure the barrier is designed for an increased traffic intensity, using a 2-lane traffic of Suezmax tankers and a 1 lane traffic of Very Large Crude Carriers. As a result of local design trends and the determination of the Net Present Value (NPV) for several protection levels, a 1/1,000 years storm event is used as feasible design storm. This storm is associated with a ‘Shifted Ike+30%’ event, which is an often used term in literature, using heavier design conditions than the last major flood of Hurricane Ike (2008). This storm holds wind speeds up to 65 m/s, a design wave height of 6 m and a surge level of MSL+8 m at the HSC entrance. In addition to the Navigational Barrier, the designed protection system consists of three levee sections and an environmental section which has the function of maintaining the natural character of the area by allowing tidal movement and coastal dynamics. The levee system is designed for the complete alignment, for the environmental section is a caisson barrier proposed which is surrounded by dunes. A Multi Criteria Analysis (MCA) has shown that a horizontally sliding gate is the most suitable option for the navigational barrier, resulting from a list of 10 proposed barrier types. A first technical design of the horizontally sliding gate is based on the proposed concept of Penland and Cibor (2013), consisting of a rectangular concrete gate. The gate cross-section is optimized, a movement mechanism is proposed and a foundation is designed, consisting of a sill structure on top of a pile foundation, to deal with the weak soil layers present in the area. Measures have been taken to meet all stability and strength requirements. Although the main objective is met by the concrete design, an alternative design is proposed which provides a better performance on aspects related to gate movement, aesthetics and structural requirements. This alternative design contains a steel triangular ‘truss’, on which a concrete water retaining wall is installed. The abutments and dry dock are integrated in the alignment of the levees resulting in a design that integrates with the landscape. Additionally, by the construction of a park, an exhibition and a restaurant, this barrier is also a “lifestyle attraction”, adding recreational and spatial value. It is concluded that it is beneficial to construct a barrier at the HSC entrance. The proposed designs provide feasible solutions for flood risk mitigation in the region.Hydraulic StructuresHydraulic EngineeringCivil Engineering and Geoscience