Archive for June, 2014

Casting pond, upper Lion Creek

26 June 2014

One of Oakland’s most beautiful places is tucked in the woods next to the Warren Freeway at Carson Street: the casting pond complex of McCrea Memorial Park, along Lion Creek. Entering the park took my breath away the first time I visited.

castingponds

Lion Creek leaves the grounds of Holy Names University and runs in a steep gorge behind Elinora Avenue, evading the freeway for a short stretch that includes the park. Horseshoe Creek joins it at the south end, and the combined stream enters a culvert beneath the freeway running to the Mills College campus.

This part of the streambed is highly engineered. The 1947 topo map shows an ordinary stream valley here with an intermittent stream indicated, so the wide glade for the ponds was built and the stream shunted aside. Farther downstream are some empty ponds whose purpose I don’t know; perhaps one of you does.

lion-creek-at-mccrea-park

The woods have made the area their own. This was once part of Leona Heights Park, which was cut in half by the freeway, and a pedestrian bridge that may be Oakland’s least-used one connects the two sides.

Hayward fault slickensides

9 June 2014

Here’s an odd curio that I spotted down in Menlo Park at the U.S. Geological Survey campus. During a trenching study of the Hayward fault up at Point Pinole, the active trace was uncovered and this plaster cast was made. It sits by the entrance of the Map Sales Room in Building 3.

HF-slicks

Today we would make a lidar scan of a surface like this to document its slickensides in a precise database. But you have to feel some affection for this low-tech artifact, which presumably has also been scanned to ensure its immortality.

Lion Creek restoration

5 June 2014

Down at the mouth of Lion Creek, at what most of us still think of as Coliseum Gardens, the authorities have undone a bit of historic damage to the habitat. A rehabilitation project dug a new channel next to the existing culvert and installed water gates at both ends to manage the flow—brackish tidal water at the Bay end and floodwater at the hill end. After four years, it’s looking the way it was intended. Here’s the view downstream from the Lion Way overcrossing, with the Coliseum in back and the Lion Creek Crossings community all around.

coli-gardens-creek

Here’s the map view. The airphoto is kinda old, but it shows you the plan.

coli-gardens-map

The ground where I was standing is mapped at about 8 feet elevation. The other end of the park is approximately where the historic coastal marsh started, so they’re doing the right thing for this location. The culvert is still there to handle floods, but a real creek bed evolves to coexist with floods. So what we have now is sort of a zoo creek. I’ll take it over what was there before.

Cost estimates vary from $4 to $5 million to create this acre and a half of habitat. Looked at another way, that’s what it costs to lose a plain old natural creek bed, doing what it does best.

More from the City of Oakland

Alameda County calls it a “natural channel”

Alameda County Flood Control district calls it “a natural bypass creek”


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