Several landslides have closed the cruise ship dock in Skagway for the rest of the summer, causing what’s expected to be at least three dozen vessels to skip the tourism-dependent port by the end of summer.

The municipality issued an emergency declaration on Aug. 4, citing the need to shore up the slide-damaged areas and the loss of more than 100,000 cruise passengers to cancellations and rescheduling.

A mid-July report from a geotechnical and environmental consulting firm showed “significant risk” of “catastrophic failure” of the mountainside above the dock that poses “signific...