Antecedent Controls on Rainfall Runoff Response and Sediment Transport in a High Arctic Catchment

In the High Arctic, late summer rainfall events have the potential to increase discharge and transport substantial amounts of sediment. Past studies have not considered the role of antecedent soil moisture with respect to rainfall-runoff response, particularly in the context of changing climate. We investigate these processes through multiple major rainfall events and the associated discharge and suspended sediment response, measured in a small watershed at Cape Bounty, Melville Island, Nunavut. Fluvial and sedimentological responses to two major rainfall events on 9 Jul. and 23 Jul., 2012, totaling 35.4 and 10.6 mm, respectively, resulted in negligible responses in discharge and suspended sediment mobilization. The magnitude and intensity of these events were not unusual in this region, but the lack of response was substantial when compared with past events of similar magnitudes. The two-week antecedent period leading up to the 9 Jul. rainfall was characterized by exceptional temperatures and high solar radiation, decreasing soil moisture and increasing infiltration potential, all of which substantially diminished the runoff and resultant suspended sediment transport. These results demonstrate that antecedent catchment conditions may substantially attenuate suspended sediment transport responses to multiple major rainfall events and decrease runoff ratios and characterization of these conditions is necessary to accurately model catchment response.