Project Summary: The existence of Yazoo clay soil in Mississippi frequently causes distress to the pavement and cause deformation at the slopes in highways and levees, which are a critical component in Maritime and multimodal transportation infrastructure. Each year, fixing the pavement requires a significant maintenance budget of MDOT. Also, the infiltration of the rainwater in the highway and levee slopes leads to landslides, which require millions of maintenance dollars each year. Due to the shrinkage and swelling behavior of the Yazoo clay, the hydraulic conductivity varies over the different seasons and has higher vertical permeability during the dry season. With high vertical permeability, the rainwater can easily percolate in the pavement subgrade and slopes, which accelerates the failure. However, a limited study is available on the change in hydraulic permeability of Yazoo clay soil. The current study investigates the change in unsaturated vertical and horizontal permeability and its effect on the maritime and multimodal infrastructures, especially on the pavement and slopes of highway embankment and levees. Highly plastic Yazoo clay soil samples were collected from highway slope sites and then tested in the laboratory to investigate the changes in the hydraulic conductivity with different wet-dry cycles. Mini Disk Infiltrometer and instant profile method were utilized to determine the hydraulic conductivity of Yazoo clay with 1, 2, and 3 numbers of wet-dry cycles. The laboratory test results indicated that the hydraulic conductivity of Yazoo clay is very low at a fully compacted phase (~10-6 cm/s). However, with an increment in the wet-dry cycles, the hydraulic conductivity of Yazoo clay increases (~10-4 cm/s) after the sample is exposed to 3 numbers of wet-dry cycles. Flow analysis was performed on a highway and a levee embankment, to investigate the effect of the changes of the hydraulic conductivity on the infiltration behavior with the presence of different rainfall volume. The flow analysis was performed using the finite element method, using Plaxis 2D. The flow analysis results indicated that with an increase in the hydraulic conductivity, the rate of infiltration increases along the slopes, and it only influences the highway pavement near the shoulder. However, the increase in hydraulic conductivity severely affects the infiltration behavior of the levee. At high hydraulic conductivity, the low intensity and long duration rainwater infiltrated through the levee and saturated the levee section. Due to the rapid infiltration of the rainwater in the levee, the matric suction value almost disappears, which leads to saturated conditions of the levee. Even though the changes in the hydraulic conductivity affect the saturation behavior which influences the stability of the highway embankment and levee slopes, it is mostly ignored in the design. It is highly recommended to include the variation of hydraulic conductivity in the design of the Maritime and Multimodal Transportation Infrastructures on Yazoo clay.