The Generation and Giant Gaps Tadpole to Colfax Iowa Hill Road River Run in California is a Class III-IV river run that spans approximately 6.5 miles. The rapids range from technical pool drops to steep chutes, and there are several obstacles to navigate, including a large boulder garden and a narrow rock chute. The best time to float this section of water is in the spring when flows are between 1,500-2,500 cfs. This section of the river is not recommended for beginner boaters, and a solid roll and rescue skills are necessary.