The South Fork begins at Martha Lake, 11,010 ft (3,360 m) above sea level,[5] near Mount Goddard in the northern section of Kings Canyon National Park in Fresno County.

[6] The Florence Lake Dam, as well as Vermillion Valley Dam on Mono Creek which forms Lake Thomas A. Edison, are both part of the Big Creek Hydroelectric Project operated by Southern California Edison to provide electricity to Los Angeles.

The concrete multiple-arch Florence Lake dam was completed in 1926 to ensure a year-round water supply for the tunnel.

The South Fork between Piute Creek and Florence Lake has a wide variety of difficulty levels for boating, ranging from a gentle, smooth meandering stream in the Blayney Meadows section to continuous Class VI to V+ whitewater in the last 2 miles (3.2 km) above Florence Lake, as well as a number of waterfalls that must be portaged.

Below the Florence Lake Dam river flows are less reliable due to water diversions, except in years of particularly heavy snowmelt.