As part of the Potter Valley or Eel River Project, a pair of dams were built across the upper reaches of the Eel beginning in 1906 to divert water to the much more populous but smaller Russian River drainage area to the south, resulting in a much higher flow in the smaller river and a significantly decreased flow in the upper Eel during certain seasons.
Although located near the headwaters, these dams can cause a significant reduction of the flow of the lower Eel River because much of the river's summer flow originates from the mountains above Lake Pillsbury.

In 1911 noted American engineer John B. Leonard designed Fernbridge, a 1,320 feet (400 m) all concrete arched bridge at the site of an earlier ferry crossing.
Now listed on the National Historic Register, Fernbridge is the last major crossing before the Eel arrives at the Pacific Ocean.
The last crossing before the Pacific Ocean is at Cock Robin Island Road a few miles to the west of Fernbridge.
Later, the Pacific Coast Highway would be constructed along the South Fork and along the Eel River downriver of the South Fork.

In 1914, after seven years of construction, the Northwestern Pacific Railroad completed a rail line running along much of the Eel River as an important transportation link connecting Eureka and the many small towns along the Eel River valley to the national rail network.
The railroad had the ignominious distinction of being the most expensive (per mile) ever built at the time: it traversed some of the most rugged and unstable topography in California, with 30 tunnels in a 95-mile (153 km) stretch.
The ceremonial driving of the golden spike was delayed by flooding and subsequent landslide damage to the rail line in October 1914.

In the 1950s, interest grew in damming the Eel River system to provide water for Central and Southern California.
After damaging floods in 1955, these dams also received support for potential flood-control benefits.
The U.S. Bureau of Reclamation and U.S. Army Corps of Engineers proposed a series of dams on the river and its tributaries, the largest of which was the enormous Dos Rios Dam near the confluence with the Middle Fork, which would provide water for the California State Water Project and control flooding.
Water would be diverted through a 40-mile (64 km) tunnel to the Sacramento Valley, where it would join the water flowing down the Sacramento River to the California Aqueduct pumps in the Sacramento–San Joaquin River Delta.
The proposal was defeated with public initiative by the early 1970s, to protect the remaining relatively wild rivers in the state.
Ronald Reagan, governor of California at the time, refused to approve the project.
The proposed reservoir would have flooded the Round Valley Indian Reservation.

In 1964, a severe Pineapple Express event, known as the Christmas flood of 1964, brought heavy rains to coastal northern California.
The Eel River drainage area was directly in the storm's path.
With no major dams to control its flow, the main Eel reached a peak of 936,000 cu ft/s (26,500 m³/s), with 200,000 cu ft/s (5,700 m³/s) from the South Fork alone.
Ten towns were obliterated with dozens of others damaged; at least 20 bridges were destroyed, and some, including Miranda and South Fork, were never rebuilt.
The heavy damage was due not only to the water, but to the huge amount of sediment and debris swept down the river, including millions of board feet of timber.
The deepest flood waters were nearly 70 feet (21 m) above the normal river level.
Several thousand people were left homeless by the floods and over 4,000 head of livestock died.

The large storms of the mid-20th century, along with the ecological changes from logging and grazing activities, almost wiped out the river's salmon run.
Due to huge earth-flows caused by the record rain in 1964, 105 million tons of sediment were carried down the Eel River between December 21–23 as measured at Scotia – more than in the previous eight years combined.
This sediment scoured away or buried spawning grounds for salmon and steelhead trout, causing the populatio
As part of the Potter Valley or Eel River Project, a pair of dams were built across the upper reaches of the Eel beginning in 1906 to divert water to the much more populous but smaller Russian River drainage area to the south, resulting in a much higher flow in the smaller river and a significantly decreased flow in the upper Eel during certain seasons. Although located near the headwaters, these dams can cause a significant reduction of the flow of the lower Eel River because much of the river's summer flow originates from the mountains above Lake Pillsbury.
In 1911 noted American engineer John B. Leonard designed Fernbridge, a 1,320 feet (400 m) all concrete arched bridge at the site of an earlier ferry crossing. Now listed on the National Historic Register, Fernbridge is the last major crossing before the Eel arrives at the Pacific Ocean. The last crossing before the Pacific Ocean is at Cock Robin Island Road a few miles to the west of Fernbridge. Later, the Pacific Coast Highway would be constructed along the South Fork and along the Eel River downriver of the South Fork.
In 1914, after seven years of construction, the Northwestern Pacific Railroad completed a rail line running along much of the Eel River as an important transportation link connecting Eureka and the many small towns along the Eel River valley to the national rail network. The railroad had the ignominious distinction of being the most expensive (per mile) ever built at the time: it traversed some of the most rugged and unstable topography in California, with 30 tunnels in a 95-mile (153 km) stretch. The ceremonial driving of the golden spike was delayed by flooding and subsequent landslide damage to the rail line in October 1914.
In the 1950s, interest grew in damming the Eel River system to provide water for Central and Southern California. After damaging floods in 1955, these dams also received support for potential flood-control benefits. The U.S. Bureau of Reclamation and U.S. Army Corps of Engineers proposed a series of dams on the river and its tributaries, the largest of which was the enormous Dos Rios Dam near the confluence with the Middle Fork, which would provide water for the California State Water Project and control flooding. Water would be diverted through a 40-mile (64 km) tunnel to the Sacramento Valley, where it would join the water flowing down the Sacramento River to the California Aqueduct pumps in the Sacramento–San Joaquin River Delta. The proposal was defeated with public initiative by the early 1970s, to protect the remaining relatively wild rivers in the state. Ronald Reagan, governor of California at the time, refused to approve the project. The proposed reservoir would have flooded the Round Valley Indian Reservation.
In 1964, a severe Pineapple Express event, known as the Christmas flood of 1964, brought heavy rains to coastal northern California. The Eel River drainage area was directly in the storm's path. With no major dams to control its flow, the main Eel reached a peak of 936,000 cu ft/s (26,500 m³/s), with 200,000 cu ft/s (5,700 m³/s) from the South Fork alone. Ten towns were obliterated with dozens of others damaged; at least 20 bridges were destroyed, and some, including Miranda and South Fork, were never rebuilt. The heavy damage was due not only to the water, but to the huge amount of sediment and debris swept down the river, including millions of board feet of timber. The deepest flood waters were nearly 70 feet (21 m) above the normal river level. Several thousand people were left homeless by the floods and over 4,000 head of livestock died. 
The large storms of the mid-20th century, along with the ecological changes from logging and grazing activities, almost wiped out the river's salmon run. Due to huge earth-flows caused by the record rain in 1964, 105 million tons of sediment were carried down the Eel River between December 21–23 as measured at Scotia – more than in the previous eight years combined. This sediment scoured away or buried spawning grounds for salmon and steelhead trout, causing the populatio
Eel River (California)