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• 60 the stream power exceeds five pounds per second per foot. Because half the anti- dune wave height is due to degradation and the other half aggradation, only one half of the calculated antidune wave height is added for diversion depth requirement. The resulting increase in depth due to antidune formation is con- sidered in the design of minor diversion channels T2, E1, Roadl, and Road2. Superelevation occurs in channel bends when the velocity is high and the radius of curvature is small. This effect can be estimated by the equation 2 E ~ V T (2) ~c in which z is the superelevation, V is the average flow velocity, q is the acceleration of gravity, T is the top width of the flow, and rc is the ' radius of curvature for the centerline of the channel. There were no signifi- ~- cant bends, flow velocities were small, and top widths are small. As a con- sequence, superelevation will be negligible for these proposed channels. By suamiing the rigid-bed flow depth, aggradation, one half the antidune • height, and the required freeboard, the required maximum diversion depth is obtained. Table 17 presents the required design diversion depths. Another factor to be considered is whether the diversions will be stable in terms of the erosion and sedimentation process. This requires sediment trans- port to be nearly equivalent in all reaches so that neigher aggradation nor degradation are excessive. In addition, flow velocities must be low enough to prevent damage to the aide slopes of the channels. Flows in the channels are relatively small due to the small drainage areas involved in most cases. As a result, most velocities and flow depths are also small and sediment transport capacity is not high. In addition, flow durations are short. Combine this with infzequrent flows, the channels should not, erode excessively. Maintenance may be required for long-term use at critical locations, but it will not be excessive. The other problem to look at when considering channel stability is flow velocity. As stated earlier, according to Chow (1954), the permissible flow velocity is 3.75 feet per second or less to provide a stable channel. This is based on the channel being located in material of graded loam to cobbles, . noncolloidal. Also, these diversions are only temporary and long-term stability is r.c= as important as for permanent designs. Maintenance can correct small stability problems.