A walk around Lake Merritt in 2100, after sea-level rise

8 January 2018

Everybody walks around Lake Merritt. I do it all the time. But I got the wacky idea of a walk that circles the lake without “touching” it — sort of a “floor is molten lava” version — and pedestrian paths count. Here’s what that would look like.

That’s a fun walk through some fine neighborhoods, and about 1-1/2 miles longer than sticking to the shore. The only quibble is at Grand and Euclid: you might be safer from the lava if you left Grand a block west, up Bellevue, but you’d miss some rare little streets and a stairway.

Then I thought, What will it be like after a century or so of sea-level rise? How would people get around the swollen lake in 2100? Laying out that walk required more care. The forecasts of future sea levels vary widely — so much depends on Antarctica and human actions — but a summary by NASA puts the worst-case upper limit at 2 meters above today’s elevation by the year 2100.

You could walk all over the lake shore and eyeball 2 meters elevation — and I did do that — but fortunately there’s a better tool available at the Risk Finder site, by Climate Central. That’s where I compiled the map below (1200 x 1000), showing the areas around Lake Merritt that would be inundated by a 2-meter sea-level rise. (You’ll also find a big page of stuff about Oakland.)

The map shows we’d lose nearly all of the shoreline roads. Along the west arm of the lake, most of Lakeside Drive would go under, and the water would reach up Harrison all the way to Whole Foods.

In Lakeside Park, the bandstand and the whole bird sanctuary would be submerged, though the rest of the park is on a Pleistocene marine terrace and would stay dry.

The east end of the lake would really take a hit. Forget the pergola — all of Eastshore Park would turn into tidal wetland, and Splash Pad Park? It’d be just Splash Park.

Grand Avenue as far as Elwood we’d have to rename Grand Canal. All the properties lining Lake Park Avenue would get their feet wet, including the Grand Lake Theatre, and a bunch of shops on Lakeshore.

Down at the boat landing, E. 18th Street would be underwater all the way to Park Boulevard, wiping out the heart of that commercial district.

And the Lake Merritt Amphitheater would mostly go under, though the roadway — Lake Merritt Boulevard — would be fine. So would the pedestrian bridge, for what that’s worth.

The geologic map shows that the new wetlands around the lake would be in areas of artificial fill (af), and because fill isn’t built up any higher than strictly necessary, it’s vulnerable to rising seas. In planning my round-the-lake walk I kept things simple and assumed the roads in these areas will be abandoned (but see more below).

Walking around the lake in 2100, you’d have to give a wide berth to “Thomas L. Berkley Creek” under 20th Street, Glen Echo Creek under Harrison, Pleasant Valley and Trestle Glen Creeks under Grand Lake, and Park Boulevard Creek under E. 18th. These detours will put you up in the hills, because that part of town is either really flat or stairstep steep. On the positive side, that terrain (lobes 3 and 4 of the Fan) is what makes Adams Point, Lakeshore and Cleveland Heights so charming.

Given all that, I came up with this 2100 Walk Around Lake Merritt.

Notice that almost none of it actually “touches” the lake. The shoreline roads will be swamped, along with each of the stream valleys entering the lake. As I field-checked this walk by eyeball, at two places in particular it looked like you’d still need wellies. One spot is Sunset Cove, at the north end of Wayne where it meets Wesley Avenue (at the end of the word “Lakeshore” on the map).

If that’s off limits (and the inundation map says it is) you’d need to climb up Newton instead and come down Stow, which would definitely call for a pizza slice from Leaning Tower (if it’s still there in 2100) to get you over that hump.

The other spot is on Harrison at the Whole Foods. If Bay Place (the continuation of 27th Street) isn’t above water, you’d have to detour up Vernon and traverse the hills of Adams Point on Lee Street to get back down to Grand Avenue. But you might as well stay up high, because the only way across the freeway, short of climbing all the way up to the Chetwood Street overcrossing and back down Santa Clara (about a half-mile detour), is the amazing pedestrian/bike crossing at the end of Van Buren Avenue. Here’s the view from the west end over I-580.

And from the end of the cage section, you can see the east end, where it winds behind the Lakeview School and then over the freeway onramp.

If I ran this city, I’d refurbish this valuable bypass with an arched cage of clean chainlink that allows better views. And while I was at it I’d build another overcrossing on the other side of Grand Lake, connecting the severed parts of Wesley Avenue, because the climb up to MacArthur and down again is oppressive (though picturesque).

And why not? Because in the next hundred years we’ll be doing a lot of building and rebuilding. Taking this walk will force you to picture your great-grandchildren’s landscape in detail. And in my vision, unlike my fever dream, the lakeside streets are too important to abandon to the rising sea. They’ll be built up. We’ll still be able to walk around the lake along the shore, and we won’t have to take the route I mapped out.

However, the buildings along the shore are a different story. Here’s a little-appreciated geological fact: as the sea rises, so will the groundwater in the dry land along the coast. Basements that are a few feet above the water table today will be permanent pools in 2100. Streets laid down on dry ground will find their roadbeds turning mushy, more prone to traffic damage. In that respect, rising sea levels will affect things much farther from shore than the tides reach.

By 2100, today’s lakeside buildings will have gone through two or three more mortgage cycles — plus at least one damaging earthquake — and will be a century older. Given that, I think the apartment buildings on Lakeshore, for instance, will be dismantled by then and their lots condemned. And the road will move onto their old footprints.

The largest and most valuable structures will stay on — the Kaiser Center and its neighbor the Lake Merritt Plaza building, the cathedral, 1200 Lakeshore, St. Paul Tower, the Grand Lake Theatre and so on. Their owners will cope by reinforcing the basement levels and installing permanent sump pumps.

Buildings of lesser prestige, despite their historic value and charm, will face hard choices well before 2100.

The city will need policies in place to handle sea-level rise. But it’s possible that everything we do to cope can be done in an orderly way. That will require far-sighted city officials, and voters, to ensure sound long-term budgets and timely bond issues.

That will be a test.

On the other hand, a lot can change in a hundred years — just look back to 1918.

This post is dedicated to the people born this year, who will be 82 years old in 2100.

Advertisements

Tour of the Fan: Lobe 6

18 December 2017

The ancient alluvial fan of central Oakland consists of eight lobes. To refresh your memory since the tour of Lobe 4, here they are labeled on the geologic map. This week I want to show you Lobe 6.

The dominant feature of this lobe is the hill on which the Maxwell Park neighborhood was developed nearly a century ago, but the hills has lesser rises around it defined by stream valleys and a freeway. I’ve named these divisions for convenience as follows.

The southern edge of the lobe is marked by changes in slope above Foothill Boulevard. The changes are definite, but the slopes are gentle. Here it is seen looking up 38th Avenue from Foothill. (All of the photo locations appear on a map at the end of this post.)

And looking down 47th Avenue past Melrose Street toward the bay.

Looking down Trask Street from Cole Street. That’s the Bay-O-Vista hillside neighborhood of San Leandro left of center in the back, and the hills above Hayward in the back center.

And looking down Camden Street from Madera Avenue onto MacArthur, with the trees of Mills College in the back left.

The higher, eastern end of the lobe is not as well defined except on its north side, shown here looking from High Street onto Bayo Street.

The other edges of the lobe are quite a bit more rugged. This is the north side of the Jefferson segment, seen from Gray Street. Just to the left of this frame is the landslide scar of Jungle Hill, which I featured in my post about peculiar Harrington Ridge.

Brookdale Park on High Street, where the Jefferson and Maxwell segments meet, offers a rare glimpse at what the Fan is made of: ancient, well-compacted clay and sand with some gravel here and there.

The Maxwell segment dominates Lobe 6 in height and area. Its steep northern and eastern faces were shaped by stream erosion from below. Here, on MacArthur just south of I-580, it may have been steepened further by development-related excavations.

Seen from across the freeway on Green Acre Road, near the top of the St. Lawrence segment, the spine of Maxwell Hill, about 260 feet high, walls off views of the bay. The dip in the foreground is one of many gulches that punctuate the lobe’s rim.

Lobe 6 is nearly severed in two places. One is where the freeway punches through, having enlarged a pre-existing saddle between the Maxwell and St. Lawrence segments. The other is where Courtland Creek cuts between the Jefferson and Maxwell segments. High Street took advantage of that gap in East Oakland’s earliest days, probably following an older footpath. The gap carved by the creek is visible in this view west down Maybelle Avenue. The church at the left edge is St. Lawrence O’Toole, perched on its namesake segment above the Laurel district.

This view south from High Street shows San Carlos Avenue crossing the valley of Courtland Creek. Courtland Street runs up the creek now, built on the old Key Route right of way.

Other small streams have carved valleys into Lobe 6, but today the valleys only carry culverts and add charm to the topography. The valley of Vicksburg Avenue, separating the Fairfax and Maxwell segments, is the headwater catchment of little 54th Avenue Creek.

More sizeable is the valley of Kingsland Creek, now culverted beneath Kingsland Avenue. This view across the valley is looking north at the north end of Walnut Street. (Did you know Oakland has two entirely separate Walnut Streets?)

Birdsall Avenue, just to the east, also runs up a nice creek valley. These “low roads” running along the stream valleys are your best bets for a pleasure walk, since the streets of Lobe 6 were otherwise laid out in a grid without ridge roads. The nearest thing to a ridge road is 47th Avenue, in the small Fairfax segment. At its top it dips into Vicksburg Valley and offers this view of Home of Peace Cemetery on the Maxwell segment, a pleasant place to visit and an easy landmark to spot from the BART train.

The high streets are a bit awkward to get around on, but they have lots of charming spots. This is where Storer Avenue sweeps around the northernmost rampart of Maxwell Hill, seen from the top of the Herriott Avenue steps.

And of course there’s the postcard view of Meldon Avenue, worth seeing even when Redwood Peak and the high hills aren’t visible.

I always enjoy tramping around here. Photo locations and a hint of the terrain below.

In other news, I will be taking the rest of the month off. Come January, I’ll throttle back my time on this blog, posting biweekly instead of weekly. More details in the Announcements/Q&A page.

The St. James Drive roadcut

11 December 2017

Recent work in far east Piedmont has exposed some excellent bedrock worth a close inspection. Because the town government won’t put an interpretive sign there, this post will have to do.

To my knowledge, there are only two sites of powerline towers in Piedmont, one at the mouth of Estates Drive and the other at 298 St. James Drive, near Park Boulevard. Last year the power company replaced the latter pair with shiny new towers, and as part of the work it cleared the roadcut of its cover of acacia trees (Google Maps shows the site as a thicket going back to 2007). Shortly afterward I discovered it and had high hopes, though it wasn’t much to look at in late October.

By January, the exposure had been stripped of loose rock. Already it was clear that it would be a showcase of slickensides.

By August, a strong concrete wall had been put in place and landscape plantings made.

The slickensides turned out to be fabulous. These are the polished marks made as movement along faults grinds rocks against each other.

And here’s a closeup.

Also visible is evidence of brecciation, the geologist’s word for shattering rocks and cementing the pieces together.

The rock here is sandstone of the Franciscan Complex, specifically part of the Novato Quarry nappe. This is a thick slice of fine-grained sandstone that was laid down off the ancient coast of California, then shoved against the continent’s edge and pulled apart into lumps by the San Andreas fault system. A bunch of it underlies Marin County, and more makes up Point Richmond and El Cerrito as well as Piedmont and points south. This tectonic history probably accounts for the wear and tear visible in the roadcut.

When I visited the roadcut again last week, I annotated and recorded the site in the ROCKD smartphone app and announced it on Twitter. I’m trying out the app just for fun as a way to make some of my observations public. I’m looking at other apps for more rigorous mapping purposes.

Geologizing on the 33 bus line

4 December 2017

My geologizing habits are unusual: being self-employed and semiretired, I go out on weekdays, when everyone else is busy and I have the landscape to myself. Moreover, most of my outings around Oakland are on foot, with the help of the Citymapper phone app and all manner of public transit, which I’ve praised before. In fact, I’ve written a whole compendium of places to see in Oakland this way.

So I’ve gotten to know the bus system pretty well. And for accessing lots of interesting, walkable terrain, the 33 line ranks right up there. Assembled from parts of the old 11 and 18 lines, the 33 runs from the bedrock hills and uplands of Piedmont, past Lake Merritt, to the bedrock hills and uplands of Montclair, taking in lobes 3 and 4 of the Fan as well.

The northern leg takes you to the well-appointed sidewalks of Piedmont, saving you a tedious climb. But there’s scenery on the way. First you pass the north arm of Lake Merritt, then cross lobe 3 of the Fan and reach bedrock right after crossing upper Grand Avenue.

Destinations in Piedmont include the former quarries of Dracena Park and Davie Tennis Stadium, the canyon and creek of Piedmont Park, and the headwaters of Trestle Glen Creek, plus smaller attractions like the slickensided roadcut of St. James Drive.

The southern leg of the 33 takes you to central Montclair, a jumping-off point for hikes in all directions. But first you pass the mouth of Lake Merritt, then enjoy a scenic ride up the valley of Park Avenue Creek and past the views over the glens (Trestle Glen and Dimond Canyon) in Glenview.

Above Glenview you could get off at Leimert Boulevard and trek through Oakmore, or go the other direction into easternmost Piedmont; your call. But then you’d miss the passage through Dimond Canyon.

From Montclair you can head west back downtown through Piedmont; north to Thornhill Canyon or past Lake Temescal to the Rockridge BART station; south to the trails of Joaquin Miller Park; or east to the high hills through Shepherd Canyon, up the Colton spine, and even all the way through Sibley Preserve, shown below, to Orinda.

None of those possibilities appear on AC Transit’s map of the 33 line, just a lot of human destinations and transit connections.

So climb aboard the 33 some time. Maybe I’ll see you there.