Topographical Features tie 
W. The width of the Coastal plain at Colville river, about Long. 151° W., is 
80 miles. It narrows towards the east to near Collinson point, about Long. 
145°W., where the upland fronts the sea. East of the Sadlerochit river, about 
Long. 144-5° W., it abruptly widens to about 50 miles and then narrows where 
the British mountains approach the ocean at the international boundary line. 
From a height only slightly above sea level the Coastal plain rises very 
gradually to a height of from more than 100 feet to more than 1,000 feet. At 
certain places, however, for instance east of Collinson point, the rise is much 
more abrupt and reaches 200 feet within a mile from the coast. Barter island 
and the area south of it form another exception, the island itself reaching an 
elevation of 50 feet and presenting a rolling surface. 
_ Locally the dead level of the Coastal plain is broken by large mounds which 
rise abruptly from the surrounding plain. These mounds usually have the form 
of rounded domes the altitude of which above the plain reaches a maximum of 
nearly 300 feet, although most of them are less than 50 feet high. They are 
especially numerous between the Canning and Colville rivers. 
_ Otherwise the Coastal plain is so featureless that there are many places in 
which one might become lost without a compass. In all directions there may be 
simply a flat tundra plain dotted with shallow lakes and ponds. Many of the 
larger rivers flow through such shallow cuts that their existence might not be 
suspected at a distance of half a mile. Banks 10 feet high are exceptional, and 
their maximum height is probably less than 15 feet. 
The drainage originating in the plain itself has established very few lines. 
The surface waters collect into ponds and lakes, and the overflow soaks through 
the grass to the nearest stream. Some of the larger lakes have definite outlets 
in the form of widely meandering surface streams which are so narrow that 
one can step across them. Some of these streams are deep and carry a large 
flow of water. 
The streams have cut gullies near the river banks and the coast but on none 
of the creeks examined do the gullies run back for more than a mile. West of 
Colville river, where the plain is much wider, the streams have probably developed 
high banks. A minor feature of the Coastal plain, yet one that is noteworthy 
in a region of such slight relief, are low, grassy hummocks, so-called ‘‘owl sites,’’! 
from one to three feet high, which are scattered sparingly over the flat tundra 
plain. They have a coating of turf and support a luxuriant growth of vege- 
tation. They were probably formed partly by the lodgment of wind-blown 
material around driftwood and boulders, perhaps also by fluviatile or morainic 
deposits. (See Plate I, fig. 1). 
In the deltas of the rivers, the banks, particularly the western, are usually 
covered with silt dunes in belts of various width. Lying off the rivers are mud 
flats with an extension generally in proportion to the size of the river and to the 
degree of protection from the waves or currents of the ocean. The land along 
the whole coast is, as mentioned above, very low, being often invisible from a 
small boat 2 or 3 miles at sea.2 Where the tundra banks come to the ocean, 
and where therefore no gravel or sand intervenes, the erosion of the waves forms 
the characteristic mud bluffs whose black, loamy muck, often resting on or 
having imbedded ground ice, shows up as a sharp, thick streak for a long dist- 
ance. Otherwise the coast line is formed by smaller sand dunes or gravel bars, 
the bars often enclosing lagoons of varying sizes. As to the formation of the 
shoals, the reader is referred to McClure’ and Collinson.‘ 
The many islands skirting the coast from point Barrow to Mackenzie 
delta, with the exception of half a dozen, all consist of the same gravel and sand 
material as does the coast and often have lagoons. Only Jones islands, Tig- 
1 These are apparently the same as the ‘‘Skua-hummocks” described from Bear Island in Barents Sea by Summer- 
hays and Elton. Journal of Ecology, Vol. XI, 1923, Cambridge, England, p, 223. See also Simpson’s Narrative. 
London, 1843, p. 177. re 
2 See also Maguire’s Report of the Plover Expedition, p. 34. 
3McClure, R., The Discovery of the Northwest Passage. London, p. 60. 
41.c, p. 363. 
