Moon Power

At the turn of the year the moon bulked up and flexed its muscles.  It heaved the waters of the Pacific to a royal high, and hours later dropped them again as if it had pulled the plug on a tub. 

At 9:36 Sunday morning December 31, a King Tide rated at 7.08 flooded parts of the foot and bicycle trail along Marina Boulevard, just opposite the Hilton hotel.  Later, at 4:43 pm, minutes before sunset the same day, the waters receded and exposed acres of wet mud at the bottom of the North Basin, in a low tide rated at minus 1.24. 

The next day, New Year’s, came an even higher King Tide, rated 7.23, at 10:30 a.m., with an even lower negative low tide, minus 1.56, at 5:30 p.m., unfortunately after sunset.  Tuesday, January 2, a 7.24 high tide is due at around 11:12 a.m., with an amazing minus 1.67 set for 6:18 p.m., in the dark.  Wednesday will see further highs and lows, not quite so extreme.  Thereafter the peaks and valleys mellow out for a while. 

The high tide of these few days equalled the highest tides seen in the year 2017, on January 11, June 22-25, and earlier in December.  The lows are in the same extreme league as the minus 1.7 tide of May 27, the minus 1.6 of June 24-25, and the minus 1.5 of December 4-5.  

As my short video made on Sunday shows (below), the tide comes in almost on cat’s feet, in soft little waves barely half an inch high.  At least that’s the case on a calm day. The maximum level occurs within a half hour of the scheduled peak listed in the NOAA tables.  A tide aficionada, Joan, disabused me of the notion that the NOAA times ruled the tides.  The peak lasts just minutes.  Little waves continue to creep in, but they don’t penetrate as far, and the net flow is out.  I made a time lapse video on Monday that shows a half hour’s advancing water in a bit over three seconds; see below.  

The City of Berkeley, which is responsible for the foot/bike path along Marina Boulevard in front of the Hilton hotel, shows no indication of caring that the much-used path floods at every high tide above 6.0.  The water comes in mainly via an obvious gap not six feet wide.  A smaller secondary gap is in the “V” where the Marina Boulevard path intersects with the Virginia Street extension.  It would take a worker with a front-end loader maybe an hour, transportation included, to plug them both with rocks, gravel, and dirt.  The East Bay Regional Parks District, which appears to be responsible for the Virginia Street side that forms the southern boundary of the North Basin, has shored up the seawall enough to prevent the pond-size floods seen there in 2012, but an obvious gap not three feet wide remains that could be plugged by a worker with a shovel in half an hour.  Neither the City nor the District see the saltwater intrusion and pathway blockage as a concern.  

The peaks and valleys of the tide make a striking drama in a shallow body of water like the North Basin estuary.  At flood tide, you can’t see the Schoolhouse Creek outfall in the southeast corner of the basin, nor the rough beach to its right; it’s all just water.  At ebb, a four-foot concrete pipe emerges, from which a meandering channel snakes out through the pock-marked mudflats toward the deeper water.  Low tide also reveals a wreck that looks like part of a steel boat of unknown origin.  (If you know something about it, please contact me!)    

An odd thing about the super low tide is that relatively few shorebirds turned out to feed.  More modest minus tides typically draw birds in large numbers, as I’ve documented here several times — for example December 15 2017, February 4 2016, and others.  I would have thought more mud, more birds.  Not so.  There’s something about the vast exposure of bottom that occurs at major low tides a few times per year that keeps the birds away.  I saw the usual hundreds of Greater Scaup and a few Grebes further out in the deeper water, mostly sleeping.  There were dozens of Coot and their freeloading companions, the American Wigeons.  I saw a modest flock of what were probably Least Sandpipers.  A scattering of Bufflehead, mostly females. Some Ruddies.  One Black-necked Stilt.  But egrets, herons, Yellowlegs, Turnstones, Dowitchers, Godwits, Whimbrels and the rest of the mud-pecking shorebird crowd — absent.  Curious are the ways of birds.   



Click on image below to see it larger:

P.S. January 2.  The King Tide around 11 this morning ran a bit higher than yesterday, but not dramatically so.  (Pic below.) When I mentioned to a couple of other tide observers that I hoped to motivate the City to plug the breach, I ran into some pushback. “Don’t do that, how will we tell the level it’s reached if it can’t flood the path?” Another couple of observers, much younger, considered jumping over the gap that lets the tide in, but thought better of it.  (Pic below)  They could have easily done it, but then where would they be?  

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