The blasting causes a small slide in 1913 and a larger rock slide on February 23, 1914 during which an estimated 100,000 cubic yards (76,500 cubic metres) of granite slide into the river just above the left bank outcrop that forms Hells Gate. It narrows the channel to 23 metres vastly increasing the river’s velocity. Work to remove the slide starts in March but has not been completed when the sockeye salmon arrive at the beginning of July.
Most sockeye are unable to pass the rock slide to reach their spawning grounds. To save some of the salmon First Nations men are hired to use dip nets to transfer fish to the other side of the slide, but this only saves some salmon. Future salmon runs are notably affected by this poor return.