The Little Susitna River originates at 1,700 feet elevation in Hatcher Pass within the Talkeetna Mountains, which form the northern boundary of the Matanuska-Susitna Valley. From its headwaters, the river flows southwest for several dozen miles before emptying into Cook Inlet. The river's character transforms dramatically along its course—beginning as intense whitewater through a boulder-choked canyon in the upper reaches, then mellowing into a meandering, clear stream through forested lowlands before reaching tidewater.

Paddlers will find two distinct experiences on the Little Su. The upper whitewater sections, accessible from the Motherlode Cookhouse & Saloon on Fishhook Road, deliver Class IV+ to Class V rapids characterized by near-continuous technical challenges over rounded granite boulders. These runs, typically paddled at flows between 350-900 cfs, demand advanced kayaking skills and are most commonly run during spring runoff. The uppermost section from Motherlode to Fishhook Road Bridge covers seven intense miles, while extending to Shrock Road increases both distance and difficulty.

Below Schrock Road, the river's personality shifts entirely. Starting at the unimproved access off Pittman Road (Parks Highway mile 48.5), floaters encounter a twisting, brushy waterway with Class I-II difficulty. This 14.5-mile section to the Parks Highway bridge at mile 57 features permanent logjams requiring portaging, frequent sweepers, and modest currents of 3-5 mph. From the Parks Highway downstream, the river becomes increasingly placid, offering 15 miles to Nancy Lake Recreation Area, then continuing another 26 miles to the Little Susitna Access Road near Yohn Lake, and finally 28 miles to Cook Inlet.

Summer flows typically range from 80-1200 cfs, with the river running warmer than most Alaskan waterways. Salmon runs draw anglers from mid-July through August, with king, red, coho, chum, and pink salmon migrating upstream. The Alaska Department of Fish and Game operates a weir upstream from the Public Use Facility to monitor salmon populations. Rainbow trout and Dolly Varden provide additional fishing opportunities throughout the ice-free season. Wildlife sightings along the lower river include black bears, mink, and various waterfowl.

The river corridor transitions from privately-owned land between Hatcher Pass and the Parks Highway to predominantly state-managed lands downstream. The Little Susitna Public Use Facility, located 42 river miles below the Parks Highway and approximately 26 miles south of Wasilla via Burma Road, serves as the primary access point for powerboats and the most popular fishing area. The facility lies within the Susitna Flats State Game Refuge and offers camping alongside boat launch facilities.

Fishing is prohibited upstream of the Parks Highway. Voluntary no-wake zones and seasonal non-motorized restrictions apply to specific sections during peak use periods from May through August.