Partial-depth, impermeable guidance structures (or guide walls) are used to enhance downstream passage effectiveness at a hydroelectric facility by actively guiding fish to a safe passage route (i.e. the bypass). Guide walls have been installed in a variety of ways and, like many fish passage devices, have resulted in variable efficiency rates. Currently, the most common type of installment is a steel panel guide wall attached to a floating boom. While less utilized than other guidance structure options (e.g. louvers and bar racks), guide walls have been gaining popularity, particularly within the Northwest United States. The aim of this dissertation is to perform a literature review on guide walls and to provide a detailed assessment on how the key design parameters of a guide wall impact the flow field. Chapter 1 is broken into two sections. First, a literature review is performed on guide walls, explaining the history of their use and their effectiveness. Second, a computational fluid dynamics (CFD) model is developed and used to evaluate the effect of several guide wall design parameters (depth, angle, and approach flow velocity). Chapter 2 provides another analysis of the hydraulic conditions upstream of a guide wall, but does so using a lab-scale model. The results of Chapter 1 are compared to that of Chapter 2. Lastly, Chapter 3 performs a sensitivity analysis by evaluating the effect of the bypass flow percentage on the key metric (the ratio of the vertical velocity component to the sweeping velocity magnitude) developed in Chapter 1 & 2.