Knik River

{{Short description|Watercourse in the United States}}

{{For|the census-designated community|Knik River, Alaska}}

{{Use American English|date=February 2025}}

{{Infobox river

| name = Knik River

| native_name = {{native name|tfn|Skitnu}}

| image = Knik River railroad bridge.jpg

| image_size = 300

| image_alt =

| image_caption = Railroad bridge on Knik River, from the Glenn Highway

| map = Wpdms shdrlfi020l cook inlet with arms.jpg

| map_size = 300

| map_alt =

| map_caption =

| source1_location = Knik Glacier

| source1_coordinates = {{coord|61|24|25|N|148|34|00|W}}

| mouth_location = Cook Inlet, at Anchorage / Matanuska-Susitna Borough

| progression =

| length = {{convert|25|mi}}

| source1_elevation = {{convert|400|ft|m|abbr=on}} drop

| mouth_elevation =

| discharge1_avg = {{convert|1500|-|60,000|cuft/s|abbr=on}}

| basin_size =

| river_system =

| tributaries_left = Hunter Creek, Goat Creek, Eklutna Tailrace

| tributaries_right = Metal creek, Friday Creek, Jim Creek, Bodenburg Creek

}}

The Knik River {{IPAc-en|k|ˈ|n|ɪ|k}} (Dena'ina: Skitnu; Ahtna: Scitna’) is a {{convert|25|mi|km|adj=mid|-long}} river in the U.S. state of Alaska. Its source is at Knik Glacier, from which it flows northwest and west and empties into the head of Cook Inlet's Knik Arm, near the mouth of the Matanuska River. It is bridged twice (old and new bridges) where the Old Glenn Highway crosses it near the Butte,{{cite book|author=National Research Council (U.S.). Committee on the Alaska Earthquake|title=The great Alaska earthquake of 1964|url=https://books.google.com/books?id=5EArAAAAYAAJ&pg=PA994|accessdate=29 April 2012|year=1968|publisher=National Academies|page=994|id=NAP:12981}} and also bridged on the Hayflats.

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 river itself is relatively shallow and wide and considered a class I float. It drops about {{convert|400|ft}} from the glacier to the salt water, or roughly {{convert|16|ft}} per mile. The {{convert|4|mi}} above the hayflats bridge is unusual in that it remains unfrozen most winters because the Eklutna project discharges warmer water into the tailrace. Discharge normally is about 5000 to 6000 ft3/s in the summer (140 to 170 m3/s), with floods of 60,000 ft3/s (1700 m3/s) or more not uncommon.{{cite book|author1=T. C. Fuglestad|author2=Alaska. Division of Geological and Geophysical Surveys|author3=Alaska Railroad Corporation|title=The Alaska Railroad between Anchorage and Fairbanks: guidebook to permafrost and engineering problems|url=https://books.google.com/books?id=s2PxAAAAMAAJ|accessdate=29 April 2012|year=1986|publisher=State of Alaska, Dept. of Natural Resources, Division of Geological and Geophysical Surveys in cooperation with Alaska Railroad Corporation}}

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 Denaina term for the Knik river was "Skitnu", (meaning Brush River).

The river runs near the border between the Matanuska-Susitna Borough and the Municipality of Anchorage. Much of its length is paralleled by the paved Old Glenn Highway and the paved (as of 2000) Knik River Road, along which can be found the community of Knik River.