21 Mar 2024

A Beneficial Placement Decision Support Framework for Wetlands: Case Study for Mobile Harbor, USA

Abstract: The US Army Corps of Engineers, in the responsibility of maintaining navigational infrastructure, has a unique opportunity to improve coastal wetland resiliency and conserve coastal natural infrastructure through the beneficial use of dredged material for wetland restoration. Opportunities are widespread, and tools such as biophysical models can aid coastal managers in assessing habitat vulnerability and planning restoration. In this study, the Marsh Equilibrium Model was utilized in concert with observed data to predict future conditions and evaluate potential effects of beneficial use of dredged material to restore marshes in Mobile Harbor, Alabama. A range of site conditions and two restoration strategies were considered, and the subsequent impact to dredged material management area volumes evaluated. Results showed that wetland restoration via the thin-layer placement of dredged material can restore marsh elevation to combat sea level rise and conserve fill capacity at dredged material management areas. This approach is demonstrated for adoption nationwide by coastal managers.

14 Sep 2023

Surge Analysis in Mobile Harbor, Alabama: Ship-Simulation Report

Abstract: A navigation channel improvement study for Mobile Harbor was conducted by the US Army Corps of Engineers, Mobile District (CESAM), and the Alabama State Port Authority. The US Army Engineer Research and Development Center (ERDC) assisted CESAM in assessing channel modifications using ERDC’s Ship/Tow Simulator through a Feasibility Level Screening Simulation study in 2017 and through a more comprehensive ship-simulation study in 2020. During the 2020 study, a safety concern was identified related to vessel interactions between a transiting vessel passing docked vessels at the McDuffie Coal Terminal located along the main federal channel. In the previous ship-simulation studies, the docked vessels were represented as targets, which means the ships are visually represented but no hydrodynamic interaction is captured. To fully assess this interaction, a surge-analysis study was completed in 2022 that used hydrodynamic models to represent docked vessels with representative mooring conditions. This study assessed several proposed navigation channel expansions across from the McDuffie Coal Terminal over the course of six testing days with four pilots. Assessment of the proposed modifications was accomplished through analysis of ship simulations completed by experienced local pilots, track plots, run sheets, and final pilot questionnaires.

29 Oct 2021

Mobile Harbor, Alabama Navigation Study: Ship Simulation Report

Abstract: Mobile Bay is a large estuary located in the southwest corner of Alabama, which connects to the Gulf of Mexico. Mobile Harbor contains the only port in the state that supports ocean-going vessels. Some of the larger vessels calling on the port experience transit delays and limited cargo capacity, so a study was conducted by the US Army Corps of Engineers, Mobile District (CESAM), and the Alabama State Port Authority to investigate channel improvements. In 2017, the US Army Engineer Research and Development Center (ERDC) assisted CESAM in screening proposed deepening and widening alternatives in Mobile Bay by completing a Feasibility Level Ship Simulation (FLSS) study using the ERDC Ship/Tow Simulator. These lower-resolution databases from the FLSS study were used as a foundation to complete a more robust navigation study in 2020 to test the proposed modifications to Mobile Harbor. During this study, three main areas were focused on: a bend easing, a passing lane, and a turning basin. Testing of the proposed design was evaluated over the course of 2 weeks with eight pilots. Assessment of the proposed modifications was accomplished through analysis of ship simulations completed by experienced local pilots, discussions, track plots, run sheets, and final pilot surveys.

27 Apr 2020

PUBLICATION NOTICE: Evaluation of the Potential Impacts of the Proposed Mobile Harbor Navigation Channel Expansion on the Aquatic Resources of Mobile Bay, Alabama

Abstract: This report assesses potential impacts to aquatic resources resulting from proposed navigation channel expansion activities within Mobile Bay, Alabama. This work was conducted for the U.S. Army Corps of Engineers (USACE) Mobile District, to support development of a supplemental Environmental Impact Statement. Changes in water quality and hydrodynamics were evaluated for potential impacts to benthic macroinvertebrates, wetlands, submerged aquatic vegetation, oysters, and fish. The assessment includes extensive characterization of baseline conditions, evaluation of estimated post-project conditions related to aquatic resource habitat (e.g., changes in salinity, dissolved oxygen). An analysis of potential impacts related to a 0.5-m sea level rise scenario were also evaluated. Results suggest that no substantial impacts in aquatic resources within the study area are anticipated due to project implementation, as the area of greatest potential changes to environmental conditions are already adapted to natural shifts in salinity (and other factors), and to conditions resulting from the existing navigation channel. Although sea level rise has the potential to alter aquatic resource habitats with Mobile Bay, additional impacts related to project implementation remain negligible under the 0.5-m sea level rise scenario.

22 Apr 2020

PUBLICATION NOTICE: SPDAT Rainfall and Streamflow Analysis at Mobile, Alabama

ABSTRACT: This Dredging Operations and Environmental Research (DOER) program technical note (TN) seeks to explain how the Storm and Precipitation Dredging Analysis Tool (SPDAT) can be used to determine dredging response to varying rainfall levels at a given site. This TN will focus on the historical dredging records in the Mobile Bay Ship Channel and rainfall levels in that area. The analysis presented in this TN will form the basis for how the tool methodology can be used to and compare rainfall and dredging records to determine response trends at other sites. The results from the tool analysis can inform dredging managers about how much dredging may be expected under similar rainfall or tropical storm conditions for future cycles.