Figure 7.   Thickness of sediment, in meters, that has accumulated in Boulder Basin and Las Vegas Bay since impoundment of Lake Mead. Sediment is thickest in the floor of Boulder Basin where it commonly exceeds 20 m, is thin in Las Vegas Bay where it does not exceed 4 m in thickness, is limited to the axial valley, and is absent from the walls of much of the lake. A shaded-relief image of the lake floor and surrounding landscape shows the strong control that the lake floor morphology has on sediment distribution.