The Coquille River
THE COQUILLE RIVER AND MAJOR TRIBUTARIES
The Coquille River and Tributaries
The 1059 square mile Coquille River watershed is the third largest river system in Oregon. The majority of the Coquille watershed lies in Coos County, Oregon. The remainder is in Douglas County and a small area of Curry County. The Coquille’s three major tributaries; the North (including the East Fork), Middle, and South Forks; join the main stem with a few miles up- and down-stream of the town of Myrtle Point and flow into the Pacific Ocean at Bandon. Table 1-2 below shows the length, average gradient, and drainage area of the Coquille River and its major forks.
Main Stem Coquille River and Estuary
Although the watershed is large, the estuary of the Coquille river is one of the smaller in the state. The lower bay of the Coquille is long and narrow, measuring about 763 acres. The estuary contains over 380 acres of tidelands, and 383 acres of permanently submerged land. Eelgrass beds, wetlands, and tidal flats provide feeding, spawning, breeding, nesting, and nursery areas for many species of terrestrial and aquatic life.
Despite the historical diking and filling of many acres of wetlands, creek, and slough environments, the lower river area continues to be a very important rearing environment for anadromous fish, such as shad and juvenile Chinook salmon. The main stem of the Coquille River stretches 36 miles from the confluence of the South Fork to the mouth, and drains an area of 172 square miles. It has a very low gradient of about one foot per mile. The City of Coquille at river mile (RM) 25 marks the observed limit of saltwater intrusion. The entire main stem is tidally influenced. The head of tide occurs at Spruce Street bridge in the town of Myrtle Point on the South Fork at RM 38.
TABLE 1-2
LENGTH, GRADIENT, AND DRAINAGE AREA
OF THE COQUILLE RIVER AND ITS FORKS
| Length | Average | Gradient | Drainage Area | ||
| (Miles) | (Feet/Mile) | Percent(%) | (Square Miles) | ||
| Main Stem | 36.3 | 1 | 0.02 | 172 | |
| South Fork | 62.8 | 47 | 0.89 | 288 | |
| Middle Fork | 40.3 | 35 | 0.66 | 310 | |
| North Fork | 53.3 | 30 | 0.57 | 154 | |
| East Fork | 33.8 | 70 | 1.33 | 135 | |
| Total | 226.5 | 1059 |
South Fork of the Coquille River
The South Fork of the Coquille River is the longest fork with a length of 62.8 miles and an average gradient of 47 feet per mile. The longest reach in the Coquille system is 99 miles from the headwaters of the South Fork to the mouth of the Coquille River at Bandon. The South Fork subwatershed contains 288 square miles.
Middle Fork of the Coquille River
The Middle Fork of the Coquille River is actually a tributary to the South Fork with the confluence just south of Myrtle Point. It runs 40 miles in an easterly direction from its mouth to its headwaters near Camas Valley. It has an average gradient of 35 feet per mile and drains an area of 310 square miles.
North Fork of the Coquille River
The North Fork of the Coquille River drains 154 square miles and joins the main stem near Myrtle Point. Running southward from its headwaters some 53 miles to its mouth, the North Fork has a gradient of about 30 feet per mile.
East Fork of the Coquille River
The East Fork of the Coquille River is tributary to the North Fork, and flows into it at Gravelford, about 9 miles from the mouth. The East Fork of the Coquille is 34 miles long with an average gradient of 70 feet per mile, making it the shortest and steepest fork of the Coquille. It runs west from its headwaters to its mouth east of Sitkum, and has a drainage area of 135 square miles.