Flood of July 21, 1975 in Mercer County, New Jersey

Water-Resources Investigations Report 51-75
Prepared in cooperation with the New Jersey Department of Environmental Protection
By: , and 



Intense rainfall during the evening of July 20 and early morning hours of July 21, 1975 caused flooding of unprecedented magnitude in highly urbanized Mercer County, New Jersey. Over 6 inches (152 millimetres) of rainfall was recorded during a 10-hour period at Trenton, the capital of New Jersey. No lives were lost but damages to highways and bridges, to industrial, business, and residential buildings, to farmlands and crops, and to water supply systems were severe. This report illustrates the magnitude of the flood and provides hydrologic data needed for planning and design to control or lessen damages from future floods. It includes discussions of the antecedent conditions and meteorological aspects of the storm; a description of the flood and comparison to previous floods; a summary of flood stages and discharges; a discussion of flood frequency; and photomosaics which show inundated areas. More than 200 high-water marks are described as to location and elevation above mean sea level.

Study Area

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Flood of July 21, 1975 in Mercer County, New Jersey
Series title Water-Resources Investigations Report
Series number 51-75
DOI 10.3133/wri5175
Year Published 1975
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) New Jersey Water Science Center
Description vi, 69 p.
Time Range Start 1975-07-20
Time Range End 1975-07-21
Country United States
State New Jersey
County Mercer
City Trenton
Other Geospatial Delaware River;Assunpink Creek
Online Only (Y/N) Y
Google Analytic Metrics Metrics page