Minor floods of 1938 in the North Atlantic States

Abstract

Five noteworthy floods occurred during 1938 in the North Atlantic States. The first flood was in January, the others were in June, July, August, and September. The floods of January, June, and August were relatively local events in Connecticut, New Jersey, and New York, respectively. The floods of July and September were widespread, reaching from New Jersey and New York to New Hampshire in generally coincident locations. The flood of September, the most severe, is described in appropriate detail in Water-Supply Paper 867; the others in this volume are in separate sections arranged chronologically. Extraordinary floods in Connecticut during January 1938 resulted from a critical combination of warm rainfall and virtual overnight melting of the accumulated snowfall of winter. Seven small streams in central and western Connecticut rose to levels on January 25 higher than those reached during the great floods of March 1936. Crest discharge of these streams approximated 100 second-feet per square mile. Ice cover was loosened and sent downstream in recurrent jams. In general, the larger rivers did not attain extraordinary stages. The Connecticut River at Hartford peaked at a stage 3.6 feet above ordinary flood level. Direct damage by the flood was relatively small. Snow cover on January 20, at the beginning of the rains, varied from 0.25 inch along the coast to 2.75 inches water equivalent in the northern part of the State. Precipitation between January 24 and 26 exceeded 2.75 inches in only three small areas. Total supply as water in snow and precipitation did not exceed 4.8 inches over any tributary area. Maximum measured flood run-off was 2.7 inches. The flood of June 1938 in New Jersey was the immediate result of a 30-hour rainstorm on June 26-27 that centered along a line extending from Odessa, Del., to Milton, N. J. Storm rainfall exceeded 5 inches over a total area of 2,900 square miles. River stages in the central parts of the storm area rose to levels that approached and on a few rivers exceeded previous maxima of record. Damage was extensive throughout the storm area, especially in Burlington, N. J., where Sylvan Lake Dam failed. The highest rate of flow per unit of area measured was 88 second-feet per square mile. However, all peak discharges were exceeded during the later floods of 1938 or by the flood of September 1, 1940, which produced discharges over 1,000 second-feet per square mile in southern New Jersey. The maximum volume of direct runoff during the flood, expressed in mean depth in inches on the drainage area, was 2.1 inches. From July 17 to 25, 1938, there was an irregular series of rainstorms over the eastern seaboard that brought more than 10 inches of rain over an area of 2,000 square miles and more than 6 inches over 23,000 square miles. Nearly 14 inches of rain fell at Long Branch, N. J. Extraordinary floods occurred mainly in the smaller tributary streams. Damage to highways, homes, factories, and crops, particularly the tobacco co-op in Connecticut, was extensive. Crest discharges at 12 gaging stations exceeded those previously observed. Maximum rates of discharge varied from 601 second-feet per square mile for an area of 2.91 square miles in New Jersey to 35 second-feet per square mile for an area of 711 square miles in Connecticut. Antecedent soil moisture prior to the storm was probably normal or a little above. The maximum volume of direct runoff was 4.75 inches in Massachusetts, 5.6 inches in eastern Connecticut, 6.75 inches in the Catskill Mountain region of New York, and 4.95 inches in the Raritan River Basin of New Jersey. Infiltration indices from 0.09 .to 0.21 inch per hour were computed, such rates being within the range defined for basins in the same areas during the floods of September 1938. The flood of August 6-11, 1938, in the Catskill Mountain region of New York resulted from heavy rains with a maximum of 8 inches at two centers. Rainfall exceeded 3 inches over more than 3,000