It is characterized by a broad flat plain with a bed of finely ground gravel and sand and silt.

During windstorms, large quantities of fine material is blown from the riverbed and deposited in locations generally downstream or west.

The 4 miles (6.4 km) above the hayflats bridge is unusual in that it remains unfrozen most winters because the Eklutna project discharges warmer water into the tailrace.

[2] The term "knik," present in the names of the river, the arm of Cook Inlet, and the glacier, as well as the communities of Knik-Fairview and Knik River, derives from the Inupiaq word igniq ("fire").

The river runs near the border between the Matanuska-Susitna Borough and the Municipality of Anchorage.