Archive for the ‘oakland water’ Category

New Lake Merritt

12 July 2013

I think it’s safe to say that everyone in town is thrilled with the improvements to Lake Merritt. After seeing the final configuration today, I’m feeling a deep satisfaction.

newlakemerritt

The new roadway and pedestrian bridge over the lake’s outlet serves vehicular traffic as well as ever, but residents and, most of all, the lake and the land get their due. The lake—actually it’s a tidal marsh—is noticeably healthier now that the tidal flow from the bay is no longer regulated with a dam. The range of the tide is greater now and the water is flushed more thoroughly. We have figured out how to trust nature with our lake. We’ll see in the future how the new lake deals with drought and flood, but I think that the city will not overreact to the occasional inundation as it might have in the past.

newlakemerritt2

The new lake is a triumph for the planners of Measure DD, where the money came from. The funds are still being spent on this and many other projects around Oakland, but I’m starting to wonder what the DD crew could do for an encore. Nature holds us in its hand with the Hayward fault, too. Can we envision better ways to live with it?

Pinehaven canyon

4 July 2013

The headwaters of Temescal Creek lie east of route 13 in a steep canyon that has no name on the USGS topo map, so I will feel free to name it Thornhill canyon. The canyon splits at the site of Thornhill Nursery, with Pinehaven Road heading left up its own canyon and Thornhill heading right.

pinehavencynterrain

Pinehaven canyon is heavily wooded with a lot of eucalyptus and is almost entirely underlain by the crumbly Sobrante Formation. It’s a beautiful place, with a nice running stream that helps keep Lake Temescal full.

pinehavencrop

Whenever I visit the high hills I can’t help but think of its hazards, so different from those down below. The risks of landslide and fire, even in the absence of earthquakes, are compounded by the narrow, winding roads as we all know from the 1991 hills fire. Pinehaven canyon has not burned since it was settled, although the 1937 fire came close. Its firefighters are served by a couple of large water tanks, the Swainland tank at the top of Fairlane Drive and another tank above Skyline at the top of Broadway Terrace. If these run dry, a pumping truck is supposed to go halfway up Pinehaven to a spot where the next lower water system can be tapped to replenish the high system.

pinehavenfiresign

Leona Canyon

23 April 2013

leonacynsign

Leona Canyon Regional Open Space Reserve is an East Bay Regional Parks District property of some 290 acres that is entirely within the Oakland city boundary. It’s got rocks.

The canyon was cut by Rifle Range Branch, part of the Arroyo Viejo stream network. The branch joins Arroyo Viejo underneath I-580 at the turnoff to the zoo. The topography is rugged. I surmise that the rifle range that gave its name to the creek was here once upon a time, because it’s the sort of place where you could shoot a lot without disturbing the rest of the city.

leonacyntopo

Here’s the geology of the same piece of ground.

leonacyngeo

The pink “Jsv” is the same metavolcanic rock (Leona “rhyolite”) found in the Leona Quarry just to the west. The green units are the familiar sedimentary rocks of the Great Valley Sequence, tilted upward so that they get younger to the east. The units, in order of age, are the Knoxville Formation (KJk), the Joaquin Miller Formation (Kjm), the Oakland Conglomerate (Ko) and the Shephard Creek Formation (Ksc). You can see that the canyon is controlled by the faulted contact between pink and green.

OK! The creek is dammed at the base of the canyon, presumably just for flood or sediment control. Maybe the rifle range used to be here. Anyway, the creek is fairly level throughout the park, creating a nice bit of habitat.

leonacyndam

As you walk up the creek, it wanders along the contact between the two major rock units, so you’ll see a mixture of boulders in the creek bed. The Knoxville is a shale with some sandstone, not very distinguished, but near its base it includes some conglomerate and breccia: rocks made of pebbles and cobbles derived from the Leona keratophyre. This example is from the high end of the trail, in the upper left corner of the geologic map.

KJk-cgl

The reserve has two paths that lead up the canyon’s sides. The Pyrite Trail goes west through the metavolcanics. It’s shady and steep. I should note that I saw no signs of pyrite on it.

leonacynpath

Along this trail you’ll see the Leona metavolcanics, kinda ragged-looking stuff that’s been chewed up and spit out a few times since it was a volcanic island arc during the Late Jurassic.

Jsv-brec

There are nice views of the other side of the canyon, which is more open and chaparral-y.

leonacynslopes

The trail up that side is called the Artemisia Trail. I’m not sure that either trail’s name means much. It passes a lot of this fine-grained sandstone.

Kjm-ss

Higher up, you get a good look at this big knob, which is a prominent part of the hills’ skyline as seen from the north. This view is from the south.

leonacynknob

There seem to be a few informal trails on it, and the view must be fantastic. But the Artemisia Trail offers superb views across the middle and south bay, too. I’ll be back.

San Leandro Creek (4)

16 April 2013

The airport area, to a land planner, probably seems like a blank canvas labeled “Raw Land.” But there’s stuff going on here.

rawland

This is where the low end of San Leandro Creek, between Hegenberger and the Nimitz, goes through some significant transitions. Here’s the Google Maps view, followed by the geologic map. The photo above is from the corner of Leet Drive at Hegenberger.

SLcreekGmap

SLcreekmap

The pink area is artificial fill. “Qhb” stands for young basin deposits, which is the zone of sediment at the very bottom of the San Leandro alluvial fan just before you hit bay mud. The darker yellow bit at the top is a belt of levee deposits, where the creek once flowed perhaps thousands of years ago. The alluvial fan has a half-dozen of these splaying out from Lake Chabot, from Elmhurst Creek on the north down to southern San Leandro.

(By the way, the topographic base of this geologic map is quite out of date. Do any of you remember the drive-in theater shown here where Kitty Lane is today? And when was Dag Hammarskjold School, so righteously named, ripped out and replaced with a public-storage joint?)

Looking south (upstream) from Hegenberger, the creek appears almost natural, with its floodplain close-hemmed by levees. At least, it has mud on the bottom and vegetation growing in it.

SLcreek1

This stretch of the creek is fenced off and inaccessible. From 98th Avenue—more precisely, looking downstream from behind the Wendy’s at the head of Bigge Street—it looks even more bucolic.

SLcreek2

Between these two points is the original Bay shoreline, a gentle transition from low grassland to high marsh that is almost totally gone from the Bay today. This part of the creek is the nearest it gets to being natural. Upstream from 98th the entire creek is walled in.

SLcreek3

This last shot is from the spot where the power line crosses the creek; as usual the land beneath is an informal public park. A hole in the fence gives access to the creek, but the going looks tough, and besides the dogs here are numerous and excitable.

SLcreek4

The creek forms the boundary between San Leandro and Oakland from here to the railroad tracks. From the tracks to 580, San Leandro spills well north of the creek because, like the village of Temescal, the city began as a town right on the creek.

Central Reservoir

8 April 2013

Central Reservoir is operated by EBMUD, but it’s much older. It’s the weird-looking steel-covered field north of Sausal Creek. This is a view looking over the reservoir from Ardley Avenue toward the hills.

centralrestop

That’s the Altenheim on the left, across I-580, and of course the LDS temple with Redwood Peak behind it.

The reservoir was built in 1910 by the People’s Water Company, which took the existing valley of a Sausal Creek tributary, hollowed out the top of its watershed and made an earthen dam. Later EBMUD assumed control of it and upgraded things considerably. However, landslides plagued the steep west bank of Sausal Creek directly east of the reservoir starting in the 1930s.

The latest set of slides, in 2006, led to a tangle of lawsuits initially aimed at EBMUD and blaming leakage from the reservoir. The lawsuits were consolidated and went to a jury trial in 2012, with Alameda County as the main defendant and the damaged land owners (two homeowners and a church) as the remaining plaintiffs. The jury found for the County. None of the media that announced the lawsuit bothered to report the outcome, and the City of Oakland hasn’t bothered to clear EBMUD’s name, but the jury dispensed justice as designed.

For 17 MB of geotechnical detail, see EBMUD’s Central Reservoir Seismic Final Report, issued in 2008. As far as engineers can tell, even the Big One on the Hayward fault won’t break the dam. But if I lived downstream, I’d keep a close eye on the dam after a truly major quake and be ready to relocate. And in the aftermath, that emergency water supply may save our lives.

Headwater landscaping

26 March 2013

The advantage of living in the highest hills is that there’s no one upstream from you. At the same time, hilltop dwellers may find it easy to forget what it’s like downstream.

gravelwash

This lot sits at the head of a stream valley at the edge of a regional park. The large expanse of impermeable pavement collects rainwater, and the terrace above it discharges more runoff in a large drainpipe. Ordinarily the ground would absorb most of the water and release it gradually, the way that trees are used to. Instead the flow that results here is strong enough to carry away a lot of gravel. Oh well, call in another truckload.

Turn around and track that water and gravel over the property line into the Regional Open Space. With the extra water, the stream is already cutting a deeper channel into its valley. As the years go by, the valley walls will slump into the stream and the trees will fall with them. A big wad of sediment now working its way downstream will clog the habitat below, smothering the bottomland and its ecosystem. Meanwhile the erosion of the stream valley will work its way headward. Eventually, within a lifetime, the spreading collapse will reach the edge of this large lot (and the neighbors’ lots) and whoever owns it will have an expensive problem. This pristine street may disappear from the map, like others before it in the Oakland hills.

I’m not giving a professional opinion here; it’s obvious to common sense. The landscape of the hills is fragile, but expert advice can make living there much more sustainable.

23rd Avenue valley

26 February 2013

Between the stream valleys occcupied today by 14th Avenue (originally named Commerce Street) and Fruitvale Avenue (Sausal Creek) is a subtle little valley that once had its own little creek. Now 23rd Avenue runs up its former course, diverting the street from the grid so typical of the rest of the neighborhood. The creek is shown on the 1877 map entering the Bay where the Embarcadero Cove Marina sits today. There seems to have been a shellmound a little south of there.

This view is looking up Foothill Boulevard where it crosses the valley. This is at the top of the marine terrace and the foot of the Fan. You can pretty much always tell where the Fan starts by following Foothill. The geologic map shows the valley splitting here with a spur running due north for a few blocks, filled with young alluvium.

23Av-Foothill

This is looking across the valley farther uphill, on E. 17th Street where Garfield Park is. The valley is a bit deeper here, and it continues to deepen as you go uphill.

23Av-E17St

At 23rd and 23rd the creek split, with its northern fork running where Highland Avenue is today. The main fork continued straight, along 23rd Avenue, and petered out by E. 30th Street right next to the Central Reservoir, which is in the Sausal Creek watershed. The stretch where the divide between the two watersheds is most pronounced is occupied by a street named, unsurprisingly, Grande Vista.

This creek is entirely covered today.


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