Block Waterfall.....

Willamette Falls

This Willamette Falls is location at Oregon City, Oregon with total height is 40 feet (12m)

The falls after the December 2006 Pacific Northwest storm swelled the Willamette river

View is downriver to the northwest. The locks are on the far left on the picture.

The Willamette Falls is a natural waterfall on the Willamette River between Oregon City and West Linn, Oregon, in the United States. It is the largest waterfall in the Pacific Northwest and the eighteenth largest in the world by water volume.

It is a horseshoe shaped block waterfall caused by a basalt shelf in the river floor. The 40 ft (12 m) high and 1500 ft (457 m) wide falls occur 26 river miles (42 km) upstream from the Willamette's confluence with the Columbia River.

Native American legends taught that the falls were placed there by a great god so that their people would have fish to eat all winter. Many local tribes built villages in the area because of the abundance of salmon that could only pass the falls at certain water levels. Native Americans still harvest Pacific Lamprey at the falls each year in the early summer.

It was first discovered by European fur traders in 1810. John McLoughlin established a land claim at the falls in the name of the Hudson's Bay Company in 1829. Oregon City, Oregon was established in 1842 near the east end of the falls, and what is now West Linn, Oregon was formed on the western shore 1843.

Navigating past the falls was not possible until the completion of the Willamette Falls Locks in 1873. This four lock canal is the oldest continuous operating, multiple lift navigation canal in the United States. The locks were sold by the Willamette Falls Canal and Locks Company to the United States Army Corps of Engineers in 1915.

The Willamette Falls Electric Company (later renamed Portland General Electric) was formed in 1888 to build a hydro-electric generation facility at the falls. Four turbine driven dynamos were built on the east end of the falls. A 14 mile (23 km) long transmission line to Portland was built, becoming the United States' first long distance transmission of electrical energy. In 1895 Portland General Electric built a second generation station on the west side of the falls. The newer plant, Station B, is still in operation with a capacity of 14,000 kilowatts. The old plant is currently part of the Blue Heron Paper Company.

The falls have been home to several paper mills beginning with the Oregon City Paper Manufacturing Co. in 1866. The Willamette Falls Pulp and Paper Co. opened on the West Linn side during 1889. The ownership of the mills has changed several times; the present day owners are the West Linn Paper Company and the Blue Heron Paper Company.

The industrialization of the area led to diminishing salmon and steelhead runs, prompting the construction of a fish ladder in 1882. A new fish ladder, built in 1971, is currently operated by the Oregon Department of Fish and Wildlife. The estimated chinook salmon run for 2007 run is 52,000.

The industrialization has also precluded public access to the base of the waterfall for well over a century. The public can view the falls from a signed viewpoint along Highway 99E, from the Oregon City Bridge, from a viewpoint on northbound I-205, and a boat in the river.

D`Artz : Willamette Falls

How waterfall Exist?.....

A waterfall is usually a geological formation resulting from water, often in the form of a stream, flowing over an erosion-resistant rock formation that forms a sudden break in elevation.

Some waterfalls form in mountain environments where erosion is rapid and stream courses may be subject to sudden and catastrophic change. In such cases, the waterfall may not be the end product of many years of water action over a region, but rather the result of relatively sudden geological processes such as landslides, faults or volcanic action.

Waterfalls may also be artificial, and they are sometimes created as garden and landscape ornaments.

Typically, a river flows over a large step in the rocks which may have been formed by a fault line. Over a period of years, the edges of this shelf will gradually break away and the waterfall will steadily retreat upstream, creating a gorge of recession. Often, the rock stratum just below the more resistant shelf will be of a softer type, meaning undercutting, due to splashback, will occur here to form a shallow cave-like formation known as a rock shelter (also known as a rock house or plunge pool) under and behind the waterfall. Eventually, the outcropping, more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. These blocks of rock are then broken down into smaller boulders by attrition as they collide with each other, and they also erode the base of the waterfall by abrasion, creating a deep plunge pool.

Streams become wider and more shallow just above waterfalls due to flowing over the rock shelf, and there is usually a deep pool just below the waterfall due to the kinetic energy of the water hitting the bottom.

Waterfalls can occur along the edge of glacial trough, whereby a stream or river flowing into a glacier continues to flow into a valley after the glacier has receded or melted. The large waterfalls in Yosemite Valley are examples of this phenomenon. The rivers are flowing from hanging valleys.

D`Artz: Waterfall