GROUNDWATER FLOW MODELING TO EVALUATE THE IMPACT OF GROUNDWATER ON STREAM BANK EROSION IN THE STONY CLOVE CREEK WATERSHED, NEW YORK

Ashokan Reservoir in the Catskill Mountains, New York, has been experiencing an increase in turbidity, which is affecting water quality. The Stony Clove Creek has been identified as the primary contributor of these sediments. The turbidity problem can be attributed to the failing slopes along the banks of the Espous Creek, and other tributaries. While increasing frequency of severe storms is a factor it is not the single cause. Localized morphology and stream patterns has lead areas of high ground water pressure. These zones of groundwater convergence create failures along the banks of the river. These banks consist of glacially derived clay material, which is the source of the suspended solids and geologic mapping was used to identify areas critical to the study. These areas are particularly prone to failure in high precipitation events because of the pre-existing ground water pressure.

A groundwater flow model has been created for an active failing site along the bank of Warner creek, a tributary of Stony Clove creek to simulate these groundwater convergence zones. Three different layers of glacially derived sediments along these banks were identfied. We utilized field surveying data as an input to make these layers in the Visual Modflow software. Hydraulic conductivity values for the different layers of sediments were calculated in the lab using permeameters. We ran the model after assigning the appropriate boundary conditions. The modeling output calibration will be performed using hydraulic head data in the piezometers that were installed in the site. We have not yet been able to simulate the groundwater zones of convergence as predicted. Additional information will be collected to run the groundwater flow model for better simulation.