ModelingMinetta a hydrological detective hunt

Photo credit Ye Liu

The brook was a brisk little affair, hurrying along in its well-defined channel, apparently as full of business as it was full of trout. Yes, of trout! They were there in abundance, darting to the higher waters like a streaks of smoke and flame, against the foamy rush of a narrow channel, or sulking under the shadow of the bank in the quiet pool below....

Old Wells and Water-Courses of the Island of Manhattan, by George Everett Hill and George E Waring, Jr, 1897

 

March 27 1901

ModelingMinetta a hydrological detective hunt Critical Dates for Reference Materials: 1782: Eric Sanderson – Mannahatta reconstruction

sources: Randall Farm Map 1820, British Headquarters Map 1782 1865: Egbert Viele – Sanitary & Topographical Map 1987: ground-penetrating radar search for old creek bed 1999: Department of Environmental Protection – reservoirs, protected lands 2000: US Census – population count 2004: NYC LIDAR elevation data 2006: Department of Environmental Protection – sewer, outfalls anecdotal groundwater source evidence

ModelingMinetta a hydrological detective hunt 1782 original stream path: Source: Mannahatta How much flow due to Stormwater? Groundwater? Where is original 1782 watershed boundary?

ModelingMinetta a hydrological detective hunt 1782 vs 2006 •  Derived from Mannahatta data •  LIDAR, streams [250 cells] Best guess surface stream flow & watershed boundary

ModelingMinetta a hydrological detective hunt 2006 Minetta Watershed Street grid

ModelingMinetta a hydrological detective hunt 2006 Minetta Watershed today Impervious surface 51% building roof * 0.95 33% pavement/walks * 0.85 11% other * 0.5 5% softscape * 0.25 Weighted average = 0.8325 If 0.1” rain fell in this watershed, ~15,000 gallons per minute would become runoff

ModelingMinetta a hydrological detective hunt 2006 Minetta Watershed today Sewer lines expand carrying capacity Assumption: groundwater flow through bedrock remains at 1782 rate

ModelingMinetta a hydrological detective hunt 1842 Croton Aqueduct Upstate water supply arrives in NYC

ModelingMinetta a hydrological detective hunt 2006 Minetta Watershed today The average New York City resident uses 125 Gallons/Day 49,725 people live in 0.624sqmi Adding an additional 6,200,000 gallons per day or 4,300 gallons per minute than original watershed would have carried

ModelingMinetta a hydrological detective hunt “Egg”-shaped sewer

ModelingMinetta a hydrological detective hunt Canal Street sewer, with inlet carrying ground water from eponymous “Spring Street” spring.

ModelingMinetta a hydrological detective hunt 1900 Modern Sewage Shed ~1940ʼs re-routed drainage: •  North River WPCP •  Newtown Creek WPCP

Minetta Watershed is divided

ModelingMinetta a hydrological detective hunt 2006 Combined Sewer Overflow +0.1” Rain = Stormwater overflow: Drainage territory shifts to •  Hudson River •  East River

ModelingMinetta a hydrological detective hunt Lalima Chemjong McMillan Helen Oi Lam Cheuk Columbia University, Summer 2010

http://vimeo.com/14647960

ModelingMinetta a hydrological detective hunt Factors affecting the Minnetta Brook in 1782:   Incoming water:

•  Rainfall [variable] •  Groundwater [Assume: 4,000 gallons per minute. Thatʼs about the equivalent of a

4ʼ diameter pipe flowing at about ½ mile per hour, which is my estimate of what the Minetta was like on a decent dry day. Near one of the sources in 1901 a contractor also hit an underground flow of 1,750 gpm in 1901. Also assume evenly spread throughout watershed, just like rainfall.]Flow rate = (1/4)*π*((pipe diameter)^2)*Velocityhttp://www.1728.com/flowrate.htm

  Flow factors:

•  Surface elevations (historic DEM) – •  Porosity (historic)

ModelingMinetta a hydrological detective hunt Factors affecting the Minnetta Brook TODAY:   Incoming water:

•  Rainfall •  Groundwater [Assume: 4,000 gallons per minute, unchanged.] •  NYC Water Supply Water from Croton, Catskill, and Delaware Watersheds

Flow factors:

•  Surface elevations (Current DEM) •  Porosity (historic) •  Sewerage elevations (models from DEP data)

ModelingMinetta a hydrological detective hunt Steve Duncan Liz Barry undercity.org lizbarry.com steve@undercity.org ebarry@gmail.com Special Thanks to: Eymund Diegel Eric Sanderson & Mannahatta GIS team Lalima Chemjong McMillan Helen Oi Lam Cheuk References: Kate Ascher The Works: Anatomy of a City Matthew Gandy Concrete and Clay: Reworking Nature in New York City Nigel Thrift From born to made: technology, biology and space