WHEN A RIVER DISAPPEARS: ANALYZING THE EFFECTS OF STREAM CAPTURE IN THE YUKON TERRITORY, CANADA

In May 2016, the Slims River in the Yukon Territory was captured by the Kaskawulsh River due to the retreat of the Kaskawulsh Glacier. This study aimed to continue the preliminary work of Shugar et al. (2017) by monitoring the effects of the stream capture for the years since 2016. River and lake gauge data for the Alsek River (downstream of the Kaskawulsh River) and Kluane Lake were studied to quantify any differences in water flow and level due to the stream capture. The average volume of water post-capture flowing into the Alsek River has increased by ~18% from the pre-capture average. Before the capture, the water level of Kluane Lake would increase by ~2m every summer. Since the capture, the water level in Kluane Lake has only reached a maximum summer increase of ~0.5m. Change in drainage area for both rivers was analyzed to determine how significant the stream capture was for downstream locations. The percent change in drainage area on the Slims River falls to 10% ~221km downstream of the point of capture, while the increase in drainage area on the Kaskawulsh River falls to 10% at ~144km downstream. Mid- and high-resolution (Landsat, PlanetLabs) satellite imagery for the years 2015, 2016, 2017, and 2018 were compared and analyzed using the Image Classification and hydrology tools in ArcGIS. Image classification results show that the wetted area in the Slims River channel has been reduced by 61.2% and the wetted area in the Kaskawulsh River channel has increased by 431% since the capture. Continued observation of this stream capture event is important to fully understand the implications of changing hydrologic systems as a result of climate change.