Pleasanton pond chain

Laguna Creek Lane area, Pleasanton Map

Much of what are now the suburban towns of Dublin and Pleasanton, in eastern Alameda County, was once occupied by huge, rush-filled Tulare Lake (Oakland Museum Map), draining by Arroyo de la Laguna to Alameda Creek. The lake was drained beginning in the 1800s. The channels that did the job are largely fenced-off ditches today.

In what once was an arm of Tulare Lake, Pleasanton is restoring one of the channels as a more natural “Bernal Creek” (not shown; work underway). The city is using chains of seasonal ponds (below) to receive runoff from burgeoning development.

Development magnifies runoff, erosion, and flooding. The ponds slow and reduce storm flows that are causing serious erosion in Arroyo de la Laguna, below.

Left, concrete “drop structure” carries water from “Bernal Creek” — itself an artificial channel — to deeply incised Arroyo de la Laguna. The creek once meandered through a marsh well above the top of the structure.

Right, rip-rap and protruding pipe on left of photo show erosion in Arroyo de la Laguna. Base of tall drop structure is in lower right of photo. Click for larger images.

Yearly removal of sediment and vegetatio, to retain flood capacity, limits the ponds’ value for wildlife and pollution control. But birds do use the ponds (City of Pleasanton photo, left)