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56 generally required if standard slopes are maintained, The steepest slope that should be con- sidered without detailed studies is a 2:1 slope ratio (2 horizontal to 1 vertical unit). Where conventional mowing equipment must be used to maintain the embankment, slopes should generally not exceed a 3:1 slope ratio and 4,1 is perferred. Riverside slopes may be less steep than the ranges presented above if erosion damage from waves or high velocity flood- waters is anticipated, 6.7 Discussion The proceeding sections presented general discussion, application and methodology for calculating the loadings that must be considered in a flood environment. The main purpose of Chapter VI waS to identify the additional loadings created during flooding and provide the methodology necessary to estimate the actual forces involved, This chapter also provides the background necessary to evaluate structural requirements for basement walls and floor slabs (Chapter XI) and tie-down requirements for mobile homes (Chapter XIV). Although this chapter is technically oriented, the calculations are relatively easy to follow. Normal structural requirements of dead, live, and restraint loads must be considered along with the conditions imposed by flooding. A structure may be subject to hydrostatic, hyd- rodynamic, and impact loads. Erosion forces can occur along channel banks and fill embankments, while scour can locally erode the soil supporting a footing or foundation. For- ces present in saturated soils can threaten the embankment stability of earth fills and levees. Table 6.6 summarizes the loadings that must be considered under flooding conditions. Application of these loadings can provide the developer with enough information to concep- tualize flood proofing requirements and do an economic evaluation, Simple calculation of these loadings can also provide planning and regulatory persons information to check or review design loads used by designers. i:, \ \ Table 6,6 loading Summaries under Flooding Conditions, Load Cause Action Hydrostatic Lateral (FH) Vertical (FV) Buoyant (FB) Hydrodynamic (FO) Impact (FI) Erosion Scour Embankment Stability Weight of Water Weight of Water Weight of Water Volume of dis- placed water Moving Water Floating debris Velocity and direc- tion of flow Local reduction in flow area, increase in velocity I ncreased weight of saturated soils Exerts pressure against submerged surface. Acts in horizontal direction on vertical or inclined surfaces. Acts in vertical direction on horizontal or inclined surfaces. Acts upward Or) horizontal or inclined surfaces. Exerts pressure on submerged surfaces. For of floatable object striking a structure. Earthen fills, el11bankments are washed out. Severe erosion at corners of buildings and embankments, around piers, piles, and walls. Slope failure or soil slippage of earth fills, levees.