Walnut Creek in Concord is a Raging Torrent

Amid the historic atmospheric river or bomb cyclone currently surging through the Bay Area, the normally-dry Walnut Creek culvert in Concord, California had transformed into a raging torrent.
As rain continued to fall, the Bay Area Telegraph observed surging, brown water flooding down the creek bed. What is usually a tiny trickle of water has been transformed into a massive river overnight, after more than 24 hours of heavy rain.
The water in Walnut Creek surged under bridges near the Hilton Hotel and Veranda Shopping Center in Concord.
Currently, the water does it appear to be overflowing the culvert. The drainage system, however, appears to be at or near its capacity.
Simultaneously, ongoing rains have led to flooding in nearby parking lots and developed areas. Part of the issue is that the ground is already saturated from the previous New Year’s day storm.
That means that the inches of rain currently falling on the East Bay are mostly flowing away instead of absorbing into the soil. Many local drainage systems empty into Walnut Creek, thus the current massive storm surge.
We are likely on the tail end of the current storm. A new storm is forecast to arrive over the weekend, though, which may lead to more extensive and ongoing flooding around the Bay Area.