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End of an Epoch at the Knapp Tract

Cris

The Knapp Tract (Salt Pond A6) has been kept dry (except for rain water) for a while now. Over the last several years it has been the breeding ground for a colony of California Gulls – on the order of 20,000 nests during the recent breeding season. In a couple of months the former pond’s levee will be breached and it will return to tidal flow. So, this is basically the last month before the current, odd landscape disappears as the next anthropogenic transition begins.

Knapp Tract, South San Francisco Bay Knapp Tract, South San Francisco Bay
Knapp Tract, South San Francisco Bay Bypass ditch in Salt Pond A6

These ground textures in the current state of Salt Pond A6 will (I presume) slowly disappear after the pond is opened to tidal flow.

In these photographs you can see the vestigial shapes of marsh channels that date back to when this area was ebb and flow marsh. Looking through old USGS quads it appears that the marsh was diked around 1950 to create a salt evaporation pond – an intervention that left levees around the perimeter pond with their typical borrow ditch just inside the levee. The northern end of the pond contains an old duck hunting club and high voltage power transmission lines. The north-south axis of the pond features a center-line levee and its borrow ditch. As always, the borrow ditches are punctuated by the scoop marks of the Mallard II clamshell dredge. The long straight centerline levee appears to have been recently manicured and it is the subject of recent interventions. From the aerial photographs it appears that the centerline levee has been interrupted in locations where a former marsh channel was located, I suppose to allow more natural water flow along the old channels after the perimeter levees are breached. In one location there is a straight bypass ditch that seems to be an alternative to additional centerline levee trenching.

Panorama from above the Knapp Tract

This panorama was made from 12 portrait format images taken with a Canon T2i with 18-55mm lens (at 18mm) lofted by a kite. I have posted a version on Flickr at 3.500 x 800 pixels. The source file itself is 22,000 x 5,000 pixels – 92″ x 21″ at 240 pixels/inch.

I was delighted when the folks at the Don Edwards National Wildlife Refuge asked if I would be interested in photographing the pond. Given a green light to visit after 1 August, I made back-to-back visits to photograph on August 5th and 6th, both toward the end of the day. This was only the second time I have flown my new Canon T2i dSLR. On the 5th I used Canon’s 18-55mm kit lens. My impression is that this inexpensive lens is not a particularly good match for the high-resolution sensor of the T2i. During the second day I used the more expensive and regrettably heavy Canon 10-22mm lens, which did a better job.

I particularly enjoyed discovering aspects of the Knapp Tract site that, while visible from the ground, escaped notice until I reviewed the aerial images. For example, the aerial views reveal the tracks of humans and small vehicles all over the place.

Here is a gallery of other images from the session, all of which were taken under my home-sewn, six-foot Rokkaku kite:

I am taking these documentary photographs under a Special Use Permit from the US Fish and Wildlife Service. Kite flying is prohibited over the A Ponds without a Special Use Permit, as is access to this part of the Don Edwards Wildlife Refuge.

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