The river has several whitewater sections that are popular for tubing and kayaking. One of these, the colloquial "Upper Farmington" section of the West Branch in New Boston, Massachusetts, is about 7 miles (11 km) long. It is Class 2 through farm and woods scenery to an iron bridge, where kayak and canoe slalom races are held. Below the bridge the river becomes Class 3-4, with a short gorge with several abrupt drops. biggest of these is about four feet at Decoration Rock. Below, the river continues fast and technical with many rocks and constant maneuvering required. The river is continuously rapid, leading through larger drops at Battering Ram rapid and Corkscrew. Eventually the river flattens to Class 2 until a final, ledge rapid at Bear's Den, just above the reservoir. The Upper Farmington is barely runnable (very scratchy with many exposed rocks and pinning possibilities) during fall dam releases, and is a much better run at levels of about 600 cubic feet per second (16,990 l/s), or about 5 feet (1.5 m) on the internet gauge for that section.