Archive for the ‘Oakland hazards’ Category

The Resilient Oakland Playbook

21 November 2016

Last month the city of Oakland released its long-awaited resilience plan, the Resilient Oakland Playbook. “Resilience” is the 21st-century name for the concept that communities can get up quickly when they’re knocked down, and avoid being knocked down in the first place.

I’ve always thought of resilience in terms of how we deal with natural hazards — earthquake, flood, landslides, sea-level rise, fire. Oakland used a definition that seems closer to familiar city politics and good-government ideas. Frankly, it read as if Mayor Schaaf had simply copied and pasted part of her recent speeches:

Resilience in Oakland means equitable access to quality education and jobs, housing security and community safety. It means building vibrant infrastructure to better prepare for shocks like earthquakes and stresses like climate change. In Oakland, resilience means catalyzing our diverse pool of talents and perspectives to tackle these challenges, both inside and outside our government, with particular focus on addressing the needs of the most vulnerable members of our community.

This will take some getting used to. The geologic hazard of earthquakes is given its due, although there are no new ideas in the playbook beyond the ongoing, snail’s-pace work of encouraging retrofits of old soft-story apartments. The Earthquake Engineering Research Institute, a major source of relevant knowledge that’s headquartered in Oakland, didn’t participate in writing the Playbook.

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Emergency preparedness is represented by a seven-month “Love Your Block” initiative in the Fire Department’s valuable CORE program. That was supposed to start in October, but there’s no sign of it on the city’s website.

The geologic hazards of climate change (a possible rise in floods and wildfires) and sea-level rise are pervasive in the Playbook. That’s OK, although I consider them remote problems. They will slowly creep up on us, noticeable only if you take a snapshot every decade. We need to make long-term plans and float bond issues to deal with them.

But there’s no mention of the mud that wipes out roads in Oakland every year. A “vibrant infrastructure” has to deal with our chronic landslides.

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The word “landslide” isn’t in the playbook once — homebuilders in the hills, you’re free to continue business as usual. Houses on alluvial hillsides, you’re off the radar.

Oakland needs the things in the Resilience Playbook. But we need more than that — we need to cultivate what Robert Muir Wood, a writer I’ve long admired, calls a disaster culture. Last month in the L.A. Times, Wood pointed to the Dutch as exemplars, citing their centuries-long effort to win land from the sea. “What Holland created — a national narrative of resilience, shared by all the people — is what L.A. (and every city threatened by natural disaster) should aspire to. Today, with the power of information technology and education, it won’t take centuries to evolve.”

Disasters don’t wait decades, and neither can we. Maybe the Playbook is how we’ll get to resilience. I’ll be happy if it is.

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Fallen trees

30 May 2016

Naturally, the people of a city named Oakland cherish their trees.

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But trees are living things, and every one must die at some point. After years of drought plus one wet winter, I’ve noticed a lot of downed trees. This one was in Leona Heights, an oak. When oaks topple, that’s the end of them.

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This one, a bay laurel, was in Joaquin Miller Park. Fallen bay trees commonly reroot, which is a handy thing in their preferred moist habitat.

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Fallen trees may interest field geologists because as their roots rip out, they expose the bedrock in areas with thick vegetation. Thus information from “tree throws” can help in mapping the rocks. For instance, I inspected the rocks uprooted by this tree . . .

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. . . and noted that they were typical mudstone of the Joaquin Miller Formation. The park is the formation’s type area, after all.

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Another treefall farther downstream exposed serpentinite. (The two very different rock types are separated by the Chabot fault.)

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Sometimes data points like these are the only way to get a handle on steep, vegetated terrain.

Research-type geologists consider “tree throw” a significant actor in the evolution of wooded landscapes (here’s a taste from a recent conference).

Down by the water, especially along the smaller creeks, fallen bay laurels often span the stream and root on both sides. Sometimes it’s charming, like here above Dunsmuir House, but it’s usually a hassle if you’re trying to walk along the streambed.

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To hydrologists — geologists who specialize in streams — fallen trees are a crucial part of stream systems. Natural streams always contain some amount of dead wood, because it lasts for years before it rots away or burns up.

Wood doesn’t act like sand and gravel. It doesn’t wash away easily, it sticks around and snags stuff. So making a realistic model of stream behavior requires a sophisticated understanding of how this “wood load” affects the water. Hydrology journals publish a steady trickle of papers on this topic.

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Most of us would rather that trees stayed standing and streambeds stayed clear. That only happens in landscaped parks. To know nature, you have to learn to appreciate snags.

The sulfur problem of the Leona rhyolite

4 April 2016

The Leona “rhyolite” is one of Oakland’s most intriguing rock formations. We have other volcanic rocks here — the true lava flows at the Sibley Volcanic Regional Preserve — but the Leona is ten times older and has a very different story.

Leona-green-Knowland

I put the word rhyolite in quotes because the rock isn’t technically rhyolite, although geologists used to think it was. Rhyolite is a type of lava, generally light-colored and very viscous, the kind of stuff you see in the Inyo Domes south of Mono Lake, or at Lassen Peak.

Instead, the Leona was originally a thick pile of mostly volcanic ash, part of a chain of volcanoes out in the deep Pacific Ocean. Volcanic ash is a glassy material. Later it was invaded by actual lava flows and hydrothermal features like the “black smokers” of the deep sea floor. These things cooked the ash beds into hard rocks as the glassy ash broke down (devitrified). The result looks somewhat like rhyolite, but it’s formally called quartz keratophyre on the geologic map. Cliff Hopson, a leading expert in this part of California geology, described it in 2008 (GSA Special Paper 438) as the top part of the Coast Range ophiolite, “mostly altered, devitrified volcaniclastic sedimentary rocks” of the “volcanopelagic remnant,” a mixture of ash and deep-sea ooze.

The hydrothermal activity, in particular, added sulfur into the mix in the form of the mineral pyrite. The mineral oxidizes upon exposure to air and rainwater, yielding sulfuric acid and iron oxides.

Over the years on this blog, I’ve documented acidic waters draining the Leona “rhyolite” almost everywhere it’s exposed. The most notorious place is the former sulfur mine at the top of McDonell Avenue, where “yellowboy” oxides stain the streambed below.

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Would-be pyrite miners have poked their picks into the Leona all over the place. I recently located a long-abandoned adit — a horizontal tunnel — left behind by one of those guys.

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You don’t want to go here. The adit is about 10 meters long, smells funny and is lined with a powdery deposit signifying a steady decay. The city ought to seal it, but it’s difficult to find and is well enough left alone, so far.

Nearby are numerous pits with the telltale red-brown linings that develop in the Leona after a few decades of exposure.

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Bits of rock below the adit, with the pyrite leached out of them, are very lightweight. Elsewhere I’ve seen this stuff turn to pure clay.

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Experience has shown me that the Leona seems to release acid drainage wherever an incision is made in it. Had I read the literature first, I’d’ve known this long ago. In a 1969 report for the U.S. Geological Survey (Map GQ-769), Dorothy Radbruch noted, “Fresh rock contains abundant pyrite in many places. . . . runoff from rhyolite hills [is] very acid and corrodes concrete sewer pipe.

Sulfur mine mitigation: An El Niño preview

4 January 2016

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Earlier this year I took a peek at the mitigation work going on at the former pyrite mine at the head of McDonell Street, in the Leona Heights neighborhood. The workers had laid down lovely geofabric, seeded grass and paved the creek bed with boulders. They were also patching infant gullies. I predicted it wouldn’t last. Sure enough, on Saturday large expanses of black plastic were shielding parts of the locality.

Farther down, the patchwork had massively failed.

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This was after a normal December rainfall. We’re looking at El Niño rainfall during the rest of the winter that will be substantially above average.

On the good side, I can report that the water downstream at Twitter Court wasn’t an ugly orange. Whether that’s due to larger runoff volume or success in muffling the acid drainage, I’m not qualified to say. Think positively as you walk past the mine site on your way up the fire road into Leona Heights Park.

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It will always be an instructive and rewarding hike.