As the rich gravels on the valley floors began to be worked out, new and more efficient methods had to be developed so that lower-grade gravels could be mined profitably. Hydraulic mining was one of these methods.
Using a pressurized stream of water to wash away overburden, hydraulic mining moves gold-bearing gravels from bench claims above the creeks. Unlike the earlier methods of placer mining, it requires a significant outlay of capitol. Instead of single claims worked by individual miners, large numbers of claims would be 'grouped' so they could be worked systematically on a large scale.
Hydraulic mining also requires a steep grade, and more importantly, abundant water, which was scarce in the semi-arid Klondike. In 1903, for instance, the Commissioner reported that the summer had been so dry that "all mining was at a standstill.”
With the construction of a series of dams and ditches, hydraulic mining did prove to be an effective mining method. In 1899, revenues from hydraulic leases were almost 20 times greater than the previous year.
The White Channel gravel is the oldest gold deposit in the Klondike district. It is also the second richest after the creek gravels.
Several million years ago, this whole region lay at a much lower elevation than it does today and the Yukon River flowed south into the Gulf of Alaska. The Klondike River likely flowed into the Stewart River, south of here, or east into the Tintina Trench. During that time, the White Channel gravel was deposited in braided streams radiating from the King Dome.
With the onset of glaciations in the Yukon approximately 2.5 million years ago, regional river drainage patterns reversed and the Yukon River was diverted north and west into Alaska along its present-day route. This, combined with an uplift of the whole area, caused the streams to flow faster and to carve more deeply into the surrounding landscape. Eventually, benches of White Channel gravel were left high above the present Hunker, Bear and Bonanza creek valleys.