Document Type

Report

Department/Program

Virginia Institute of Marine Science

Publication Date

9-2017

Series

Special report in applied marine science and ocean engineering ; no. 456.

Abstract

Previously the VIMS modeling group has studied the impact of channel deepening on the water quality in lower James River, including Norfolk Harbor and Elizabeth River. A study of the response of the water quality to future Sea Level Change (SLC) is required by present USACE guidance (ER 1100-2-8162 and ETL 1100-2-1). ETL 1100-2-1 recommends analyzing the effects of SLC on the projects at three future time periods of post-construction, including 20 years, 50 years, and 100 years. The future change of sea level is mainly caused by the sea level rise (SLR) in this region. This document provides results for water quality model simulations with future SLR to assess the impact of SLR on change of water quality in the lower James River. Since the rate of future SLR is unknown, the USACE guidance specifies that the evaluation should consider the three different SLR curves (low, intermediate, and high) included in the USACE’s online SLR calculator. Fig. 1 shows the high (red), intermediate (green) and low (blue) SLR curves from the USACE calculator, along with markers representing values projected by VIMS in a 2013 study of recurrent flooding in Virginia. The figure includes nine yellow “x”s indicating the SLR values at the three future time periods at each of the three curves. Through the course of several PDT meetings a recommendation is developed to model the effects of a single future SLR value of 3.3 feet to represent a value indicative of a 50-year high level, 100-year intermediate level, and a +100-year low level, as suggested by Fig. 1-1. Selecting a single water level allows the use of a manageable number of additional hydrodynamic and water quality modeling scenarios (four simulations) to represent the range of effects of SLR that would be projected to occur within the Project’s design life. Altogether, four simulations will be added to the eight (8) physical scenarios already being modeled by VIMS. As SLR is not considered a high risk parameter in the plan selection or in evaluating the cumulative project impact, a decision was made to model a single water level. This document provides model results and key findings related to environment assessment, particularly, changes of dissolved oxygen and flushing capacity due to SLR. For detailed model descriptions of hydrodynamic and water quality models and model calibration and verification, readers are referred to a project report submitted earlier (Shen et al., 2017).

DOI

https://doi.org/10.21220/V5GM8Z

Keywords

sea level change, oceanography

Available for download on Sunday, September 30, 2018

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