Fern Ridge project data

Dam length 6,330 ft 1,929.3 m
Height 44 ft 13.4 m
Elevation (NGVD*) 379.5 ft 115.7 m
Lake length 4.5 mi 7.2 km
Area when full 9,000 ac 3,688.5 ha
*National Geodetic Vertical Datum

Contact us about Fern Ridge:
General: 541-684-4300
Recreation: 541-942-5631

Email us about Fern Ridge

Fern Ridge pamphlet

Comment on the Long Tom River drop structure modification:

The public can also submit comments via e-mail, written correspondence or electronically (GIS):

Mail: U.S. Army Corps of Engineers, CENWP-PM

ATTN: Kat Herzog or Sarah Knowles

P.O. Box 2946

Portland, OR 97208-2946


Fern Ridge Dam & Reservoir

Fern Ridge Dam and Lake

Fern Ridge Dam is at river mile 23.6 on the Long Tom River, a tributary of the Willamette River, about 12 miles west of Eugene, Ore. Fern Ridge is an earthfill structure with a gated concrete spillway and outlet works for regulating lake levels, which was completed in 1941 at a cost of $6 million. Since then, it has prevented more than $415 million in potential flood damages. The reservoir provides 110,000 acre-feet of usable flood control storage and controls runoff from a 275 square-mile drainage area.

Fern Ridge Dam was the first Willamette Valley dam constructed by the U.S. Army Corps of Engineers. Its authorized purposes are flood risk management, water quality improvement, irrigation, fish and wildlife habitat and recreation.

Long Tom River

Long Tom Watershed Stats:

  • Total drainage area 410 sq miles
  • Drainage area above Fern Ridge Dam: 275 sq miles
  • Drainage area below dam to Monroe: 116 sq miles
    • Three main inputs below Fern Ridge: Amazon Creek 62 sq miles (39 below diversion), Ferguson Creek 25 sq miles, and Bear Creek 30 sq miles
  • Length of improved Long Tom channel below Fern Ridge Dam is 23.6 miles
  • 941 channel below present day Fern Ridge Dam was 36.5 miles
  • 88 foot overall drop from Fern Ridge Dam to Willamette River confluence 

Fern Ridge and Long Tom History:

  • 1936 Flood Control Act initiated studies of the Willamette River basin.
  • In June 1938 Fern Ridge was the first project approved by the study.
  • By Dec 1941 the dam was constructed and in operation.
  • Primary Project authorized purposes: flood control, irrigation, and navigation
  • Secondary authorized purposes: fish & wildlife enhancement, water quality, and recreation
  • During Dec 1941 discharges of 2,200 CFS resulted in Long Tom channel flooding over 1.3 miles wide extending some 7.5 miles downstream.
  • Lower Long Tom channel enhancements were approved by May of 1943.
  • Modifications were complete by 1950.
    • 119 real estate tracts from were deeded from 1942-48. Most are 300 foot wide Perpetual Easements. Total acquisitions = 905.3 acres.

Operational History:

  • Design velocities for 3,000 CFS releases from Fern Ridge were 4.6 f. p. s. (not to exceed 5.0 f.p.s. with 2.0 feet of freeboard).
  • The channel was designed to contain a maximum release rate of 5,400 CFS for short periods.
  • Observations prompted the Fern Ridge Water Control Manual to increase the max controlled release to 4,000 CFS in Nov 1950 to take advantage of the “actual improved capacity.” Normal maximum releases were lowered to 3,000 CFS after findings of a channel capacity study were received in 1988. The study found that the 4,000 CFS standard had greatly increased gravel deposits, erosion, and bank sloughing.
  • The 1988 study also found that roughness, specifically vegetative growth, had slowed velocities enough to exceed freeboard in some 9.5 miles of channel at the maximum release rate.
  • Currently the water control manual charges us to remain below bankfull stage of 4,650 CFS at Monroe and less than a 3,000 CFS discharge from the dam for normal operations.

Long Tom River drop structure at Monroe

The City of Monroe identified a Corps-constructed drop structure as a fish passage barrier and the historic channelization of the Long Tom River as a factor in the disconnection of nearby side channels in a letter of interest on August 8, 2016. The Long Tom River is a priority watershed within the Willamette River system because of its potential high-quality juvenile salmon rearing habitat, as well as spawning and rearing habitat for cutthroat trout, lamprey and other native species. 

The Confederated Tribes of Siletz Indians (CTSI) submitted a signed letter on August 31, 2020 stating approval by Tribal Council of their co-sponsorship with the City of Monroe for a project to study the removal of this drop structure. 

The Long Tom Watershed Council (non-governmental organization) is a partner to the Sponsors on the project. 

The project has two goals and a number of objectives.

Goal 1: Restore Quality Habitat for Native Fish and Wildlife Species.

  • Objective: Improve year-round aquatic habitat diversity associated with in-stream features, for native fish use of spawning, rearing, and overwintering.
  • Objective: Reconnect and restore the historic disconnected channel segments to promote a more natural hydrologic regime.
  • Objective: Restore adjacent riparian and wetland habitat.

Goal 2: Restore and Emulate Natural River Processes, Structures, and Functions to Improve Fish Passage and Maintain Channel Conveyance.

  • Objective: Improve fish passage at Monroe’s drop structure.
  • Objective: Maintain channel conveyance
  • Objective: Restore side and main channels’ hydrodynamic, sediment transport, and geomorphic processes to sustain long-term fish passage.

The Corps and its partners held and recorded a virtual public information session, November 3rd, 2021 from 4-5 p.m. You can view it here. The slides are available here.

Fern Ridge recreation

Boaters: Click here to view Fern Ridge's water surface elevation map.

Birding: The Fern Ridge area is an excellent location for birding. Oregon’s largest breeding colony of purple martins can be found at Fern Ridge. Thousands of acres of emergent marsh support summer breeding habitat for a variety of water-bird species. Read more about purple martins: Corps reservoirs benefit Willamette Valley Swallows.

Day-use parks: Fern Ridge Lake has three day-use park operated by the U.S. Army Corps of Engineers. They have no associated fees. 

Kirk Park is located below Fern Ridge Dam off Clear Lake Road and gives access to the Long Tom River and ponds full of fish and wildlife. There are no group picnic areas or shelters available for reservations. Kirk Park has trails, picnic tables, paved roads, fire rings and vault toilets. Kirk Park is open dawn to dusk, mid-May to early September. Shore Lane Park is located at the end of Shore Lane Road on the northeast shore-line of Fern Ridge Lake.  This small, rustic park has a vault toilet and it is often used for launching paddle craft.  Shore Lane Park is open dawn to dusk, mid-May to early September. Jeans Park is located on Jeans Road on the west side of Fern Ridge Lake near Veneta. This wooded park has trails, vault toilets and limited parking. It is open year-round. For more information about the above parks, call the Willamette Valley Project Park Ranger Office at 541-942-5631.

Four day-use sites at Fern Ridge are operated by Lane County Parks: Orchard Point Park, Perkins Peninsula Park, Richardson Park and Zumwalt ParkCall Lane County Parks at 541-682-2000 or visit their website. Richardson Park also has a life jacket loaner station available.

Three day-use sites at Fern Ridge are privately operated. Eugene Yacht Club, Fern Ridge Shores (or call 541-935-2335) and Tri-Pass Ski Club (541-935-1495).


Getting around

Environmental stewardship at Fern Ridge Dam

The Fern Ridge Project encompasses more than 11,000 acres, ranging from open water to marsh, wet prairie and upland prairie habitats. More than 5,000 acres of the Fern Ridge Wildlife Area is managed cooperatively with the Oregon Department of Fish and Wildlife. In addition, the Corps works with the Oregon Department of Fish and Wildlife to support resident game and non-game fisheries within the Long Tom River Basin.

The Willamette Valley Environmental Stewardship program focuses on restoring degraded uplands, wetlands and streams on Corps lands. Recent efforts include replacing exotic and invasive plants with native trees and shrubs, and restoring hydrology and topography to support native plant communities and wildlife habitat. The upland prairies and extensive wetlands at Fern Ridge provide habitats for a variety of plants and animals. Fender’s blue butterfly and its host plant, Kinkaid’s lupine, occupy upland prairie habitat around the lake.

Oregon’s largest breeding colony of purple martins is at Fern Ridge, as well as significant populations of breeding western pond turtles. Thousands of acres of emergent marsh support the summer breeding habitat for a variety of water-bird species.

Native upland prairies, along with wet prairies, now cover much less than one percent of their former area, making them some of the rarest North American ecosystems. Remnants of these highly diverse, complex and poorly understood ecosystems provide necessary habitat for many rare species. More than 50 rare species can be found at Fern Ridge, including several species federally listed as threatened or endangered.

The Fern Ridge Lake Shoreline Management Plan was developed in 1988 and revised by Addendum in 1997. Also, view these related materials: Moorage Guidelines.