4 - Sedimentary Processes in the Hudson River Estuary

Summary

abstract The Hudson River estuary is narrowly confined in its rocky valley. Unconsolidated sediments available to the estuary are primarily glacial till and glacial lake deposits. Estimates of sediment sources to the estuary range between 365,000 and 1.02 million metric tons (MT) y⁻¹ at the head of tide with an additional amount to be added along the tidal estuary of between 80,000 and 390,000 MT y⁻¹. Tidal resuspension and transport is important throughout the estuary but fine-grained sediment transport associated with the recirculation of salt water is confined to the lower reaches. A substantial marine source of sediment is likely, but of uncertain magnitude. Two turbidity maxima appear to be generated by different mechanisms. One is formed near the head of salt and migrates down the estuary during times of high freshwater discharge. The other arises in mid-estuary. It is generated by tidally modulated and geomorphically controlled salinity fronts. A marine source of sediment is likely to be substantial.

Introduction

The Hudson River estuary, or the lower Hudson as it is sometimes called, begins where the tidal influence is first felt at Troy, New York, 240 kilometers (km) north of the Battery. From this point, the combined discharge of the upper Hudson and Mohawk rivers collects additional water from the drainage basins of twenty other, smaller tributaries. The intrusion of salt water is limited to the lower reaches and can extend 120 km above the Battery at times of low freshwater discharge.