By Vladimir Brezina
These tropical storms have certainly stirred things up! Hurricane Irene came through ten days ago and deluged the entire region, and a couple of days ago Tropical Storm Lee repeated the performance. This morning, looking out of the window on Manhattan’s Upper East Side, we saw a strange sight in Hell Gate…
Hell Gate is the three-way confluence of the Lower East River (to the right in the photo below), the Upper East River (through Hell Gate proper, under the bridges to the left rear), and the Harlem River (to the left front). In the middle (behind the two tall buildings) is Mill Rock island. (Click on the photos to expand.)
About two hours after the start of the ebb in the East River, a powerful ebb current was bringing blue Long Island Sound water down the East River. But, demarcated from the blue water by a meandering but sharp boundary, the Harlem River water was a light, even slightly reddish, brown.
The complicated boundary between the blue and brown water changed as we watched over the next couple of hours, in a nice visualization of the complex dynamics of the currents in Hell Gate (well known to us as kayakers!).
Interestingly, boat wakes cleaved through the brown water to blue water underneath, revealing a vertical separation as well:
What was the brown stuff?
It could have been runoff sediment. Huge amounts of silt and mud have been coming down the Hudson River (to which the Harlem River connects at its other end) ever since Irene:
The sediment flux from Irene is really massive…unusual, but not unheard of,” said coastal oceanographer David Ralston of the Woods Hole Oceanographic Institution. “One big event like this can move and deposit as much sediment as you might get in several years of regular flow on the Hudson.
The runoff has brought down with it, too, vast quantities of larger floating debris—tree branches, logs, and all kinds of plastic trash—that have accumulated in embayments around the harbor, and which the skim boats of the Army Corps of Engineers are busy scooping up.
Altogether, New York Harbor has taken quite a few hits this summer. In July, there was the massive sewage release from Manhattan’s North River Wastewater Treatment Plant that closed beaches and disrupted recreational activities and businesses throughout New York City. Soon after, there was another significant sewage spill at Ossining that spread sewage up and down the Hudson River. And now, the lasting mess made by Irene and Lee…
On the bright side, though, the fast ebb current due to Irene’s runoff has contributed to at least one swim record in New York Harbor…