The events of Hurricane Katrina in 2005 prompted the US Army Corps of Engineers (USACE) to commission studies to identify the failure mechanisms of levees and I-walls. This involves updating of the current USACE Engineering Manual (EM) 1110-2-1913, "Design and Construction of Levees," which uses Blanket Theory for seepage analysis. Blanket Theory entails analytical methods for calculating seepage pressures and flows beneath levees. The revision of the manual will address the design seepage criteria for levees, with a focus on incorporating new seepage analysis procedures besides Blanket Theory. Finite element analysis is one such method that has more recently become the method of choice for general seepage analyses in geotechnical engineering. The focus of this research is mainly on underseepage analyses of levees in the lower Mississippi valley using numerical modeling, with a goal of helping engineers in making the transition from current Corps methods to finite element analysis. General guidelines are provided to conduct seepage analysis using finite element analysis for pre-defined Blanket Theory cases as well as for the design of seepage berms. In addition, the 3D finite element modeling is conducted for a full-scale field load test involving complex geometry and stratigraphy, which is useful in better understanding the response of levees and I-walls. / Ph. D.