Galveston Bay Houston Ship Channel project, calculation of project impact, TAMU/ODU oyster population dynamics model

This document describes the procedure used to estimate the impact of the enlargement of the Houston Ship Channel on the oyster populations of Galveston Bay over a 50 year period from 1999 to 2049. The impacts are calculated from simulations using the TAMU/ODU population dynamics model coupled to the WES hydrodynamics model under three hydrologies, present, 2024, and 2049, and under three freshwater inflow regimes, low, mean and high flow. The impacts have been calculated using two simulation strategies. One uses a standard simulation of the oyster population dynamics model and one uses a reduced level of low-salinity mortality. The rationale for the second simulation using a reduced level of low-salinity mortality is described in reports accompanying the results of the simulation. The estimates of impacts are calculated using oyster distribution in Galveston Bay derived from two data sets, one from Galveston Bay National Estuary Program (GBNEP) health assessment and one from the Texas Parks and Wildlife Department (TPWD) stock assessment program. A comparison of impact estimates was made using these two data sets. A description of each of the steps in the procedure used to estimate the impact of channel enlargement is included as well as the data underlying the calculations presented in tabular form.