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For culverts we recommend design for the 25-yeaz event with some freeboazd. This <br />assumes excess flows will breach the road and return to the channel on the other side. <br />For culvert slopes of 2-percent a 30-inch CMP will carry approximately 30-cfs and a 36- <br />inch CMP will carry approximately 50-cfs. We recommend a 30-inch culvert for <br />crossing in the upper reach and a 36-inch culvert for crossings in the lower reach. <br />