Nearly 200,000 people have been evacuated in California after a hole in Oroville Dam threatens to cause a catastrophic flood in the area. The dam is located about 75 miles north of Sacramento and is the tallest dam in the nation. Reuters reports after heavy rain last week a large gouge opened in the dam's main spillway -- and more storms are forecasted for later this week. With Lake Oroville filled to the brim..officials say a 30-foot wall of water could come crashing out of the reservoir. The Los Angeles Times reports the emergency spillway was used for the first time on Saturday....in its 48-year-old history. On Monday, state water resource officials assessed the damage and repaired erosion with rocks and boulders that were dropped by helicopters. Sand bags were also being used in the effort.