Effects of Stream Restoration and Bank Stabilization on Suspended Sediment in Tributaries to the Upper Esopus Creek

Science Center Objects

Introduction The upper Esopus Creek watershed is located in the eastern Catskill Mountains of New York State and covers 497 km2 from Slide Mountain, the highest peak in the Catskills at 1,274 m, to the Ashokan Reservoir at 193 m elevation (fig. 1). Suspended sediment and turbidity are primary water quality concerns in the Ashokan Reservoir watershed, part of the New York City Catskill-Delaw...

 

Introduction

The upper Esopus Creek watershed is located in the eastern Catskill Mountains of New York State and covers 497 km2 from Slide Mountain, the highest peak in the Catskills at 1,274 m, to the Ashokan Reservoir at 193 m elevation (fig. 1). Suspended sediment and turbidity are primary water quality concerns in the Ashokan Reservoir watershed, part of the New York City Catskill-Delaware water supply system that supplies more than 10 million people a day with clean drinking water. Stream corridor assessments of tributaries to the Upper Esopus Creek by Ulster County Soil and Water Conservation District, New York City Department of Environmental Protection, and State University of New York at New Paltz summer undergraduate researchers have revealed that some tributaries have distributed and concentrated sources of suspended sediment and associated turbidity. Distributed sources of suspended sediment include surface runoff from terrestrial portions of the watershed and stream bank and stream bed erosion during storms. Concentrated sources of suspended sediment include eroding hill sides and stream banks, particularly when these areas intersect glacial lacustrine deposits.

Stream bank and stream bed stabilization projects are scheduled to take place in the Beaver Kill, Stony Clove, and Warner Creek (a tributary to Stony Clove) watersheds beginning in 2012 and continuing for several years. These projects are intended to help reduce suspended sediment and associated turbidity in the streams. Proposed projects include the removal of a large woody debris dam, a possible bridge extension, stabilization of eroding hill slopes, and streambed realignment. Changes in stream suspended sediment and turbidity concentrations are important measures needed to assess the effectiveness of stream stabilization projects.

 

Approach

Monitoring of streamflow, suspended sediment concentration, and turbidity is conducted at the outlet of each watershed, with additional monitoring stations along the stream channel located above and below individual stabilization projects.  Suspended sediment concentrations and turbidity are determined by collecting stream water samples through the range in flow conditions. These data will be used to: 1) analyze the relation between suspended sediment concentration and turbidity, 2) develop stage-to-discharge rating curves, 3) analyze the relation between streamflow and suspended, 4) analyze the relation between streamflow and turbidity, and 5) calculate sediment loads. These data will be collected before, during, and for several years after completion of stream stabilization projects to evaluate the effectiveness of the stabilization projects on reducing suspended sediment and turbidity concentrations and sediment loads within the monitored watersheds. Additionally, longitudinal stream sampling will be conducted along the length of the 3 streams through the range in streamflows to identify the location of significant concentrated sources of suspended sediment and turbidity and distinguish those sources from distributed sources. The results of longitudinal stream sampling will also be used to isolate the effect of each individual stream stabilization project within the watersheds.

The results of this project will provide the Ashokan Watershed Stream Management Program, the New York City Department of Environmental Protection, Ulster County Soil and Water Conservation District, and other watershed planners and managers with the information needed to determine the effectiveness of stream stabilization projects.

Project
Location by County

Catskill Region: Delaware County, NY, Greene County, NY, Schoharie
County, NY, Sullivan County, NY, Ulster County, NY