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. 40 nor degrades. The method and procedure for determining equilibrium channel slopes for natural channels is shown In the design example in Section 5.2.2.2. Normally, a slope of from 0.2 to 0.6 percent for grass lined channels as recommended in Section 2.3.lC of "Major Drainage" in the Urhan Storm Drainage Criteria Manual, Volume 2, will be satisfactory. Slope could be steeper if the channel is lined with concrete or riprap. . . 3.5 Degradation and Aggradation A long reach of river channel may be subjected to a general degradation or aggradation of the bed level over a long period of time. Degradation and aggradation must be accurately anticipated; otherwise, foundation depths may be inadequate or excessive, depending on the magnitude of degradation or aggradation. The basic principle of degradation and aggradation is to compare, in a reach, the sediment supply and the sediment transport. When sediment supply is less than sediment transport, the flow will remove additional sediment from the channel bed and banks to eliminate the deficit. This results in degradation of the channel bed and possible failure of the banks. If the supply entering the reach is greater than the capacity, the excess supply will be deposited. Degradation or aggradation can be evaluated qualitatively as described in Section 2.2.2 of this report. Unfortunately, the best methods to quanti- tatively predict sediment transporting characteristics of a waterway are difficult, time consuming, and require specialized knowledge of the subject for proper application. This makes them impractical for use by the design engineer and thus, the sediment transport is either ignored or determined by inappropriate methods. This points to the need for a method of analysis . . . . . . . .