Archive for the ‘Oakland streams and water’ Category

Oakland geology ramble 3: Knowland to Dunsmuir Ridge

7 November 2016

This ramble is special for its surprising woodsiness and remoteness. I’ve seen enough deer bones along the way to guess that if any mountain lions live on this side of the hills, this is where they are.

The route is a bit less than 4 miles long and has 500 feet of elevation gain in the middle. You go up the valley of Arroyo Viejo starting at the Oakland Zoo entrance, over the drainage divide in Knowland Park, then down through the twin canyons of Upper Elmhurst Creek, a tributary of San Leandro Creek. So, there’s a lot of woods:

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A lot of hills:

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And a lot of rocks:

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This post has been a long time in the making because I wanted to try all the options. The photos are from this summer, when I explored it in earnest.

Take the 46 or 46L bus line to the zoo entrance. From there, walk in through the gate and turn left. There’s an unsung trail, dotted with seating and signage, that shows off the creek here.

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The trail crosses the creek and connects with a fire road. Soon after that, the stream valley splits and you have two routes — the northern one is the fire road, and the other is a tiny trail along the spine of the odd, narrow ridge that runs for about half a mile between the two creeks. I prefer the northern route for its rock exposures and the southern route for its seclusion and its views, like this one of the new zoo facility under construction.

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The two routes rejoin where Golf Links Road and Elysian Fields Drive meet. If you like, rummage in the creek bed and examine the fresh-scrubbed rocks of the Knoxville Formation.

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Walk carefully up Golf Links and take the fire road into Knowland Park. This part is steep, but the views open up nicely.

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And the rocks suddenly change to Franciscan melange. Knowland Park’s rocks are a destination in themselves, as I’ve pointed out here a few times.

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At the top of the park’s broad, flat crest you have three route choices. The western route slots through Snowdown Avenue, the central route through Cameron Avenue, and the eastern route through Lochard Street. I’ll show them in that order. Please note that off of paved streets, the routes are just rough lines, not precise plots.

For the western route, take Malcolm Avenue and then Montwood Way down into the headwaters of the north branch of Upper Elmhurst Creek. The fire road at the end of Montwood takes you into real wildlands.

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Bear left and head down into the valley. A fresh landslide blocks the fire road and exposes the Leona rhyolite.

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Although I call these fire roads, I think they’re really sewer roads because they all seem to serve sewer lines for the Chabot Park Highlands neighborhood.

After you cross the creek and head downsteam, the route gradually climbs out of the stream valley and takes a sharp left at the fence at the top of the Dunsmuir House property. Here it intersects with the middle route.

The middle route is picturesque because it follows Kerrigan Drive along the ridge between the two branches of Upper Elmhurst Creek. The ridge ends in a knob that widely visible, as seen here from Lochard Street.

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At the end of Kerrigan is a fire road leading to the right that goes down to the edge of the Dunsmuir House land and meets the western route.

The combined route runs level across a well-formed faceted spur, which reflects the action of the Hayward fault just a hundred meters or so to the west. Then it turns up the valley of the south branch of Upper Elmhurst Creek.

This branch should be considered the main stream of the creek, as it runs at a little lower elevation than the north branch. I suspect that the two branches may have drained in separate directions at times in the past. It would be too easy for a landslide along the fault to divert the northern stream to the right — or to the left as it runs today, for that matter. This is dynamic terrain.

Both streams are distinctly incised into their beds by up to several meters.

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This catches my attention because the hillsides are very steep, steep enough that a strong earthquake would send landslides down and clog long stretches of these streams. The last one of those was in 1868. This is an observation that applies generally to streams in the Oakland hills.

The route eventually crosses this creek and turns back west. As it climbs away from the creek it becomes a steep and narrow footpath. In due course you join the eastern route in Dunsmuir Ridge Open Space. I would tell bicyclists not to bother with this particular creek and try the eastern route instead.

The eastern route goes down Lochard Street almost to its end, where a fire road cuts off to the left. This is a very pleasant stroll through our oak-laurel forest that includes more exposures of Leona rhyolite.

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The road leaves the woods in Dunsmuir Ridge Open Space, where the view south overlooking Sheffield Village is completely different from the view west in Knowland Park.

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From here you head downhill to civilization, taking either the fire road or the footpath through the woods. They rejoin where the combined west and central route arrives, right at the trace of the Hayward fault.

To meet your public-transit needs, the 75 bus comes through Marlow Drive every hour. If you miss it, and you usually will, it’s a level walk of 2 miles to the San Leandro BART station or a shorter one to Foothill Square.

Relish our local water

24 October 2016

Next month, East Bay MUD will finish shutting down its 80-year-old Orinda water treatment plant for six months of rehabilitation. For the last few weeks, Oakland residents have been drinking water from our own local San Pablo and Upper San Leandro reservoirs.

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Consider this a once-in-a-lifetime opportunity to savor artisanal water from local watersheds. True, much of the water in these reservoirs is pumped there from our main source, the Mokelumne River in the Sierra Nevada. But just last week nearly two inches of rainfall fell on these watersheds. More will come.

The water from Upper San Leandro Reservoir is piped through the hills to EBMUD’s treatment plant in Oakland just north of Keller Avenue and west of I-580, seen here in Google Maps. The San Pablo Reservoir serves a plant in El Sobrante.

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There the raw water undergoes a series of physical and chemical operations to make it safe and potable. This is the stage that they screwed up in Flint, Michigan, by changing the water source but not adjusting the treatment to the new water.

We treat water as a utility that comes out of faucets, but water’s not like electricity — it’s a varying natural product that needs constant, professional attention. All water starts out wild. Even after treatment, water changes its taste from time to time. It’s always healthy, though, especially compared to raw water.

Think of the next few months as a visit to the past. A hundred years ago Oaklanders were getting their water from local wells, local water companies, or Lake Temescal (1868) and Lake Chabot (1870), two impoundments created by Anthony Chabot to support the growing city. The water was purified with simpler methods including sand filtration. The San Pablo (1919) and Upper San Leandro reservoirs (1926) were the first new surface storage built in generations, and this winter we’ll be relying on them as mainstays.

Follow your reservoirs every day on the EBMUD site.

This post about Oakland groundwater got a long, productive set of comments.

Tiny steps toward flood control

8 August 2016

More than once on this blog, including last week, I’ve described streams as sleeping creatures that wake up in floods. Kittens that turn into tigers, nebbishes that become the Incredible Hulk, pick your own metaphor — streams do most of their geological work in spasms. The downpour that happens once in a century, filling a creek and scouring its streambed a bit deeper and wider, is one hour in a million hours.

Last week one such rainfall made a shambles of Ellicott City, Maryland. Hydrologist Anne Jefferson looked at this flood with a geologist’s perspective. Her insights apply here as well as there.

Oakland’s Lake Merritt is prone to floods as well as high tides. The tides are slowly growing as sea level rises, of course, but the greater threat of flood comes from the land side. Oakland’s soil absorbs much less rainwater than it used to. As Oakland grew, its dusty streets were sealed under asphalt, its grassy lots occupied by homes with guttered roofs, its footpaths paved over in concrete. Today these impervious surfaces shed the rain, and the runoff drains swiftly away to the nearest body of water.

In October 1962 the Columbus Day Storm dumped over 4 inches of rain in a single day. Lake Merritt rose more than 7 feet and left the surrounding roads waist-deep in stormwater. A few years later a large flood-control station was installed at 7th Street that regulates the tidal lake.

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We can do better on the land side. Greener building practices, sustained from now on, will gradually offset our disruption of the local hydrology. This is one of those — panels of pervious pavement flanking the street trees near the lake on East 18th Street. They’re made of a porous concrete that lets water through, like a super mulch. They let the tree roots breathe, too.

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Another green practice you’ll see near the lake and elsewhere around town is rain gardens, shallow basins filled with vegetation that catch and absorb rain runoff before it can reach the lake.