This creek, in south San Jose, is now flowing due to the
release of water from Anderson Reservoir, the largest in the
Santa Clara Valley.

Due to concerns of the dam failing in the event of a major
earthquake, the resevoir was to be kept at 68% of capacity.
But with the constant rains, it is now near full.

Apparently the giant outlet pipe has been fully open since Jan 9.

http://www.morganhilltimes.com/news/updated-even-with-anderson-nearly-full-water-storage-concerns-remain/article_8b587268-ef28-11e6-b565-337db7ab15b3.html