Dalles \Dalles\ (d[a^]lz), n. pl. [F. dalle a tube, gutter, trough.]

A rapid, esp. one where the channel is narrowed between rock walls. [Northwestern U. S. & Canada]

The place below, where the compressed river wound like a silver thread among the flat black rocks, was the far-famed Dalles of the Columbia. --F. H. Balch.

Source: Webster's Revised Unabridged Dictionary (1913)