Feedback: Designing the Dredge Cycle

1100 AM EDT WED OCT 31 2012

The National Weather Service’s Hydrometeorological Prediction Center issues its final official prediction for the storm, Remnants of Sandy Advisory Number 37: “…WINDS…ACCUMULATING SNOWS…AND RAIN FROM THE REMNANTS OF SANDY CONTINUE TO DIMINISH…” [1]

Yet the effects of Hurricane Sandy linger.

Homes on Staten Island, the Rockaways, and the Jersey Shore have been tossed inland by floodwaters, broken apart, or burnt by fires. Floodwaters dislodge contaminated sediments from Superfund sites [2]. The US Army Corps of Engineers sends its “Dewatering SWAT Team” to lower Manhattan, where it “removes more than an Olympic-size swimming pool’s worth of water per minute from New York’s flooded mass transit tunnels” [3]. Sand has filled streets, beaches have been thrown back at the city, and it will take months to sort, clean, and replace the sand. “That is a job so big that, in one stretch of the Rockaways alone, the process has been going on 24 hours a day, seven days a week, for more than a month — truckload after truckload of sand being poured through super-size versions of children’s toy sifters” [4]. Fifteen thousand water-damaged cars sit at a remote airport on Long Island, awaiting auction [5].

The damage wrought on the New York and New Jersey coast by Hurricane Sandy, the subsequent efforts to cope with that damage, and plans to put systems in place that could defend the coast against future storms all received significant media attention in the wake of the storm. But another topography scrambled by Sandy was much less reported, though it is essential to the economic life of the New York metropolitan area: the carefully-managed underwater contours of the harbor and its bays. After Sandy, ports along the east coast path of the hurricane were closed, including the Port of Virginia in Hampton Roads and, of course, the Port of New York and New Jersey, in large part because the underwater approach terrain leading to those ports, usually groomed by dredgers to match the lines delineated on NOAA’s navigational charts, had suddenly been rendered uncertain, potentially containing hazardous underwater debris or otherwise blocked by storm-induced shoaling. In order to re-open the ports, NOAA deployed its “navigation response teams” to urgently re-chart harbor bathymetry, in a vital act of emergency landscape measurement [6]. After the surveys were completed, the emergency dredging began, repairs to ensure that no unseen hazards would interfere with the arrival and departure of container ships, oil tankers, and the other commercial vessels plying the harbor [7].

Dredging, the very activity that restored the clean geometries of the harbor channels after the storm, is, in conjunction with a range of other sedimentary handling practices, also responsible for exacerbating the damage produced by the storm. If, as we contend, dredging constitutes a sedimentary infrastructure essential to the functioning of contemporary coastal urban systems, then the first important thing to recognize about this sedimentary infrastructure is that it is rife with feedback mechanisms. To illustrate this, we’ll turn to Jamaica Bay.