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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />- 36 - <br /> <br />new damage versus probability curve can be constructed, and a <br /> <br />new equivalent annual flood damage potential calculated. <br /> <br />If flood damages within the existing channel are small <br /> <br />compared to the total flood damages, then Figure 2 can be used <br /> <br />to compute flood damages of channelization alternatives. <br /> <br />Basically, it is only necessary to know the carrying capacity <br /> <br />of the stream without channelization and the capacity with <br /> <br />channelization. For example, the stream under study has a <br /> <br />capacity of 2,000 cfs. Channelization will increase that capa- <br /> <br />city to 5,000 cfs - an increase of 3,000 cfs. The 100-year flood <br /> <br />damages are now the equivalent of (20,000-3,000) = 17,000 cfs, <br /> <br />or $1,200,000. Flood damages will also be reduced for the <br /> <br />other recurrence intervals and can be estimated by shifting <br /> <br />3,000 cfs on the peak discharge scale. A new damage probability <br /> <br />curve can be constructed and the equivalent annual flood damage <br /> <br />potential calculated for the channelization alternative. If <br /> <br />flood damages within the existing channel cannot be neglected, <br /> <br />then an overbank flood damage versus probability curve must be <br /> <br />constructed by subtracting the amount of the damage within <br /> <br />the channel before this procedure can be used. <br /> <br />Step 10 - Compute Flood Damaqes and Averaqe Annual Flood Damaqe <br /> <br />Potential for Alternatives <br /> <br />Repeat Steps 8 and 9 for each flood control alternative <br /> <br />under consideration. <br /> <br />~ Leonard Rice Consulting Water Engineers, Inc. <br />