Flood Magnitude and Frequency of the Delaware River in New Jersey, New York, and Pennsylvania

Abstract

From September 2004 to June 2006, the Delaware River in New Jersey, New York, and Pennsylvania experienced three major floods that caused extensive damage. The Federal Emergency Management Agency (FEMA) needed updated information on the flood magnitude and frequency for the eight active streamflow-gaging stations along the main stem Delaware River in New Jersey, New York, and Pennsylvania that included the three recent floods in order to update its flood insurance studies. Therefore, the U.S. Geological Survey (USGS) computed updated flood magnitude and frequency values following the guidelines published by the Interagency Advisory Committee on Water Data in its Bulletin 17B. The updated flood-frequency values indicate that the recurrence interval of the September 2004 flood ranged from 20 to 35 years, the recurrence interval of the April 2005 flood ranged from 40 to 70 years, and the recurrence interval of the June 2006 flood ranged from 70 to greater than 100 years. Examination of trends in flood discharges indicate no statistically significant trends in peak flows during the period of record for any of the eight streamflow-gaging stations.

Simulation of Runoff and Reservoir Inflow for Use in a Flood-Analysis Model for the Delaware River, Pennsylvania, New Jersey, and New York, 2004-2006

“…The river length from the confluence of the West Branch Delaware River and the East Branch Delaware River at Hancock, N.Y., to Trenton, N.J., is approximately 200 mi. Watershed characteristics are briefly summarized in this report; additional detailed descriptions are provided by previous investigators, including Schopp and Firda (2008), Ayers and others (1994), Parker and others (1964), Fischer (1999), and Fischer and others (2004).…”

“…The magnitude and recurrence of floods have been evaluated by many previous authors and updated as the period of record has been extended. Schopp and Firda (2008) evaluate flood frequency and magnitude for the main-stem Delaware River to Trenton, N.J., updating the statistical model of flood recurrence using data from the three recent flood events. Roland and Stuckey (2007) present flood-frequency models for selected smaller streams in the basin.…”

Maximum known stages and discharges of New York streams and their annual exceedance probabilities through September 2011

“…Flood frequency statistics at streamgages with at least 10 years of record and substantial regulation or urbanization were calculated from statistical analyses of annual peak discharges during the regulated period only, except for three sites along the main stem of the Delaware River at Callicoon, N.Y. (USGS Site ID 01427405); above the Lackawaxen River near Barryville, N.Y. 01428500; and at Port Jervis, N.Y. (01434000); these frequency statistics were calculated as part of a multiagency workgroup (Schopp and Firda, 2008) and have not been updated. These sites, indicated as "Urban" or "Regulated" in table 1, are not weighted with results from regional flood-frequency equations because these equations are only appropriate in rural settings.…”

Flood of June 26-29, 2006, Mohawk, Delaware, and Susquehanna River Basins, New York

“…No adjustments were made for the amount of available storage in the reservoirs before or during floods, or for changes in regulation procedures during the period of regulation. Recurrence intervals at stream-gaging stations along the main stem of the Delaware River from Callicoon, NY, to Montague, NJ, were computed by fitting systematic annual peak-discharge data to a log-Pearson type III distribution for the entire period of record (Schopp and Firda, 2008).…”

“…4. ***Sites in green indicate recurrence intervals computed from statistical analyses of annual peak discharges using the entire period of record and agreed upon by a multi-agency committee (Schopp and Firda, 2008 0.10 1.00 10 100 1,000 10,000 100,000 1,000,000 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 WATER YEAR ANNUAL PEAK DISCHARGE, IN CUBIC FEET PER SECOND Figure 7A. (A-1, A-2) Annual peak discharges through 2006, and discharges of the 10-, 50-, and 100year recurrence intervals for selected stations in the Mohawk River basin, NY.…”