Landforms of British Columbia 1976 - Department of Geography

It flows out the west arm of Kootenay Lake and crosses the Selkirk Mountains to
join the Columbia River at Castlegar. This southern looping of the Kootenay River
and the northern looping of the Columbia around the north end of the Selkirk Moun-
tains are not normal stream patterns and probably are the result of post-glacial diver-
sion and major stream piracy. The details of drainage history are not fully known,
and the partial interpretation that headward erosion of the ancestral Columbia River
beheaded and captured part of the head of Kootenay River to form the “ Big Bend ”
of the Columbia only suggests what the general explanation might be.
Smaller tributaries of the Columbia that drain an important part of southern
British Columbia are the Kettle, Okanagan, and Similkameen Rivers. These rivers
drain the southern parts of the Monashee Mountains and the Interior Plateau.
COASTAL DRAINAGE
A number of rivers in the western part of British Columbia rise on the eastern
side of the Coast Mountains and flow westward through them to the sea. Of them
the largest are the Alsek, Taku, Stikine, Nass, Skeena, Dean, Bella Coola, Klinaklini,
and Homathko Rivers, of which the Stikine, Nass, and Skeena are the largest.
The Stikine River rises in Laslui Lake (about 3,900 feet elevation) in the south-
ern part of the Spatsizi Plateau and flows 335 miles westward across the Stikine Pla-
teau and through the Coast Mountains to the sea, a few miles north of Wrangell,
Alaska. During its course acmss the plateau it is joined by the Klappan, Tanzilla,
Tuya, and Nahlin Rivers, which drain much of the Stikine Plateau. In the Boundary
Ranges close to the Alaska Border it is joined by the Iskut River, which drains the
southern part of the Tahltan Highland and a segment of the Boundary Ranges. The
river has a normal dendritic pattern, which developed during the long period of
erosion in the Tertiary and which was maintained against the Pliocene uplift of the
Coast Mountains.
An interesting and scenic stretch of the Stikine River is the Grand Canyon
upstream from Telegraph Creek, through which the. river flows for 40 miles, in
part between near-vertical lava walls rising to heights of several hundred feet. The
canyon was eroded in Recent time by the river after jt was forced from its old
valley by the outpouring of fluid basaltic laws from Mount Ed&a (see p. 50).
The Nass River rises at about 3,900 feet on the eastern side of the Klappan
Range in the northern part of the Skeena Mountains. It flows southwestward for
about 236 miles to the ocean at Nass Bay on Portland Inlet (see Plate XLVIIB).
The river drains part of the western side of the Skeena Mountains and flows through
the Nass Basin, where it is joined on the north by the Bell-Irving River and on the
south by the Cranberry River. Much of its drainage basin is within an area of
heavy precipitation, so that despite the fact that its drainage area is less than half
that of the Stikine, its average flow is comparable.
The river downstream from Aiyansh for a length of about 5 miles is flanked
on the south by vertical cliffs of black basaltic lava of very recent age. The lava is
derived from a small cone on Tseax Creek 3 miles east of Lava Lake, from which
flows and scoriaceous material poured northward down the creek valley, forming
a lava plain where the larger valley of the Nass was reached and forcing the Nass
River against the northern side (see p. 57).
The Skeena River rises at an elevation of more than 4,000 feet in the northern
Skeena Mountains east of the head of the Nass River. It flows southward and
westward for 360 miles to the sea just south of Prince Rupert (see Plate XLIIIB),
It drains most of the Skeena Mountains, the western part of the Nechako Plateau,
the Bulkley and Nass Ranges, and the northern Kitimat Ranges by its chief tribu-
taries, the Babine, Kispiox, Bulkley, Zymoetz, Kitsumkalum, and Ecstall Rivers.
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