Polar Bear Pass, located on Bathurst Island (75°40′N, 98°30′W) in the Canadian High Arctic, is a large ecologically important, low-lying wetland that receives water inputs from streams in the surrounding hillslopes. Most of these hillslope streams are gravel-bed streams; however, some streambeds are moss lined. One of these vegetated streams was selected to determine how vegetation influences run-off processes (e.g. water storage and streamflow) in comparison with a similar-sized gravel-bed hillslope stream. During the 2009 and 2010 field seasons, snow cover, melt and streamflow measurements were collected in both streams. Frost table and soil moisture conditions were monitored weekly along four cross-sectional transects in each stream basin, and vegetation inventories were conducted in July 2010. The active layer developed more quickly in 2010 than in 2009, yet the thaw depth remained thinner in the vegetated stream in both years. In 2009, prolonged rainfall of low intensity and meltwater inputs from long-lasting valley snowbeds maintained streamflow. Warmer and drier conditions in 2010 caused the stream to eventually cease flow, only regenerating after intense rainfall. Moss plays an important role in modifying streamflow later in the season when low-flow conditions persist, acting as a barrier to streamflow as the moisture deficit of the vegetation must be satisfied before streamflow can regenerate. Results indicate that there is a threshold that determines whether vegetation promotes or hinders streamflow and that this factor will have important implications in response to changing climate conditions for this site and other arctic landscapes. Copyright © 2015 John Wiley & Sons, Ltd.