Nizina River

At medium stage, the number of channels increases, and finally at flood height, the entire flood plain becomes covered from bank to bank with swift-flowing, muddy water carrying large quantities of sand and gravel.

Below Young Creek the bordering mountains are separated by a wider valley in which the river has cut a deep trench through the gravel and shale formations.

Finally, for the last 2–3 miles (3.2–4.8 km) of its course, the river flows between walls of solid rock, forming a box canyon for much of the distance.

[1] Chitistone River rises in Russell Glacier near Skolai Pass, about 25 miles (40 km) northeast from its confluence with the Nizina.

It is subject to extreme floods, usually one or more each year, which are caused by the clogging of the subglacial channels that open up with an immense flow after enough water has accumulated to produce sufficient pressure to force out the obstruction.

McCarthy Creek then gradually bends toward the west, and for the last 3 miles (4.8 km) flows about northwest.

Below the East Fork the stream flows between high gravel banks, meeting here and there ledges of shale and porphyry through which it has cut its way, forming small canyons.