Depth and Discharge at Burke Avenue Bridge
A pressure transducer was installed at the foot of the Burke Avenue Bridge in the Bronx Forest in April, 2002, by the Natural Resources Group. The instrument calculates water depth from measurements of water column pressure.
Depth is used as a proxy for measuring discharge. Discharge, or streamflow, is the volume of water that flows past a fixed point per unit of time. It affects floodplain dynamics, instream habitat and water quality. Because discharge can't be measured continuously with a fixed instrument, an elevation-discharge rating curve is used to estimate streamflow from depth. The velocity distribution at Burke Avenue Bridge was used to calculate streamflow.
Burke Avenue Bridge depth data is periodically downloaded from the depth sensor to a laptop computer. Water depth is converted to water surface elevation. The sensor elevation was calculated from elevation surveyed at the top of the Burke Avenue Bridge.
Stream velocity was measured across a cross-section 20 feet south of the Burke Avenue Bridge. Measurements were taken on the following dates: November 11, 2002; March 13, 2003; April 12, 2003; May 12, 2003; June 5, 2003 and June 6, 2003. The cross-sectional area of each segment was multiplied by the segment velocity. The volumes were summarized across the section to find total discharge.
To produce the elevation-discharge rating curve, stream depth and flow velocity were measured on the following dates: November 20, 2002; April 3, 2003; June 25, 2003; September 30, 2003; August 13, 2004; August 16, 2004; September 2, 2004; September 30, 2004. Water elevations were based on crest stage gage height surveyed by USGS.
Bronx River Depth at Burke Avenue Bridge
June 19 - December 31, 2002
January 1 - December 31, 2003
January 1 - October 13, 2004
April 4 - August 1, 2005
Elevation-Discharge Rating Curve