On the basis of past and recent field observations, the specific habitat requirements of Newcomb's snail include fast-flowing perennial streams and associated springs, seeps, and vertical or overhanging waterfalls. Surveys of main stream channels of many of the perennial streams of Kaua`i indicate Newcomb's snail is only found in areas protected from high scouring flows within main stream channels. The limited occurrence of this snail in main stream channels is likely due to periodic channel scouring by sediment, rocks, and boulders that are moved downstream during high flow runoff events. Consequently, suitable habitat is generally restricted to protected, small, spring-fed tributaries, or to stream segments with overhanging waterfalls that have perennial flows supported by stable groundwater input. The common element among sites harboring snail populations is that the water source appears to be consistent and permanent, even during severe drought.