In Spring Hill, early 20th Century houses look out over cinematic views of downtown Pittsburgh. The front of 36-year-old resident Randal Miller’s home appears fine, but the back is a mess. Part of it was slammed by a landslide this February. Landslides have always been an issue for the city due to its steep hills, clay soil and narrow valleys, but they usually occur in late spring and early early summer. Winter is typically Pittsburgh’s driest period, which is good, because the soil at that time is very wet as plants have yet to sprout and pull water from the...