3.1. River sampling
We used 22 samples to characterize OC supply from the rivers. These samples cover a range of grain size classes as they were collected within the river waters, on the river banks, delta-top plains, and in the river plumes at the fjord surface (Fig. 2). The sampling campaign was conducted on 26 October 2017 (Figs. 2 and 3; Fig. S3), when the Homathko River discharge was 390 m3/sec (Water Survey of Canada, 2020). This is higher than the 250 m3/sec average annual river discharge on the Homathko River, and lower than its ~800 m3/sec average summer peak discharges (Water Survey of Canada, 2020).