A technical hydrologic account documents an extreme October 1903 flood in the Passaic River basin, reporting about 11.74 inches of rainfall concentrated in roughly 36 hours and contrasting it with a smaller 1902 event. It analyzes flood timing, stages, and discharges at key dams and gauges (including Dundee, Beattie’s, and Pompton), traces contributions from Highland tributaries and rivers such as the Ramapo, Pequanac, and Wanaque, and catalogs urban and agricultural damages in Paterson, Passaic, and the lower valley. The report evaluates observed flow phenomena, presents photographic and diagrammatic evidence, and appraises reservoir and catchment projects with preferred sites and general preventive recommendations.