DISCHARGE RATES AND FLOOD VOLUMES FOR GLACIAL LAKE PASSAIC, NEW JERSEY
Bankfull discharge for the Chatham sluiceway is 1,800 m3/s, at a velocity of 3 m/s, and for the Moggy Hollow sluiceway it is 1,500 m3/s, at a velocity of 8 m/s. The Great Notch sluiceway was initially cut by flood discharge during the 24-m drop from the Moggy Hollow to the Great Notch stage, which released 10.4 km3 of water. Bankfull discharge for this channel is 3,500 m3/s, at a velocity of 7 m/s. At this rate, the flood would take about a month to drain. Drainage of the Great Notch stage released 5 km3 through the Weasel Brook sluiceway. Bankfull discharge in this channel is 5,000 m3/s, at a velocity of 5 m/s. At this rate, the flood would drain in 11 days.
The 1903 flood of record for the lake basin, which is equivalent to the modern Passaic River basin above Paterson, discharged 960 m3/s, so the maximum glacial discharge was nearly double the maximum meteoric discharge. At the glacier's terminal position, drainage from 38 km of ice front exited the basin through Moggy Hollow. The bankfull discharge of 1,500 m3/s implies a maximum melt rate of 3,800 m3/day of ice per meter of ice front, assuming no meteoric contribution. This melt rate converts to 0.13 m/day of ice-surface lowering over the 30-km length of glacier in the basin, assuming stagnant ice with no resupply. This lowering yields an ice-front retreat rate of 45-50 m/yr. In contrast, ice-margin chronology gives a retreat rate of about 30 m/yr during deglaciation in Lake Passaic. This discrepancy shows that the glacier was not stagnant.