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i." . . I I I I I I I I I I I I I . I I Body Geometry S' IT d Human Hazard to human life due to Imp I Ie flood waters occurs mainly at Geometry depths greater than six inches. At depths below six inches, unrealistically high velocities are required to cause instability. Above waist depth, the effects of buoyancy generally tend to overcome the stability of the person even at very low velocities (the individual begins to float, therefore increasing the hazard). The legs and lower d torso then receive most of the forces due to flood waters. While the legs may be considered as piers obstructing flow, their close proximity causes considerable turbulence, thereby reducing the effective flow between them. For purposes of this analysis, the Direction of flow human form was considered to be a "body monolith" composed of a rectangular block with the broad face Figure 1 Idealized "Body Monolith" ~~ Face Width Thickness B situated perpendicular (normal) to flood flows (Figure 1). This configuration represents a conservative estimate of the body structure with respect to flood exposure. Hydraulic Forces During a flooding event, the design monolith is subject to a variety of forces (Figures 2 and 3). These forces include: Direction of Flow W - weight of the design monolith B - buoyancy Ff "''''m.. P _ dynamic water force due to velocity Ff - friction F u - hydrostatic upstream force Fd - hydrostatic downstream force ) Vmax @0.8d Theoretical Velocny Distribution p fu Fd Vmin @Gl' w Figure 2 -5-