Dutch Flat Afterbay is an instream reservoir on the Bear River. Both Dutch Flat #1 (PG&E) and Dutch Flat #2 (NID) powerhouses discharge into the afterbay.

Made of earth-rock, it is165 feet high and 495 in length.

The afterbay was constructed in 1964-65 as part of the Yuba-Bear Hydroelectric Project.

Storage capacity is 2,037 acre-feet. Dutch Flat Afterbay environmental flows go into the Bear River, with current requirements at 5-10 cubic feet per second (CFS) depending on the season. The afterbay provides the diversion in the Bear River for the Chicago Park Conduit.