Cumulative forest disturbances decrease runoff in two boreal forested watersheds of the northern interior of British Columbia, Canada

•Cumulative forest disturbances significantly decreased annual runoff.•Cumulative forest disturbances and climate variability additively reduced annual runoff during the entire disturbance period.•Annual runoff responses to cumulative forest disturbances were dynamic, depending on dominated disturbance types and post-disturbance forest dynamics.