MOBILE, Ala. - Mobile District coastal engineers and engineering technicians regularly get up before dawn and head out to the middle of Mobile Bay, but not for any type of ritualistic recreation activity. Their mission is to service gauges that are part of a data collection effort in the bay and delta for the Mobile Harbor General Reevaluation Report (GRR).
The U.S. Army Corps of Engineers (USACE), Mobile District, is conducting comprehensive engineering, economic, and environmental studies to determine the costs, benefits and impacts of widening and/or deepening Mobile Harbor. As part of this study, gauges have been placed in Mobile Bay and the Mobile-Tensaw Delta to collect data that will be used to assess the existing conditions within the project area. These existing conditions will be used as a baseline for comparison to conditions resulting from any proposed channel modifications.
“The Corps uses these instruments to measure water level, wave height, turbidity, salinity and suspended sediment concentration,” said Richard Allen, one of the district’s coastal engineers. “The Mobile Harbor GRR study includes an extensive field-data collection effort in assessing the feasibility of deepening and widening the federal navigation channel in Mobile Bay.”
In late 2015, Allen partnered with the Corps Engineer Research and Development Center (ERDC) to install six continuously operated gauges. The majority of data collection occurs north of the U.S. 98 Causeway, in the Mobile-Tensaw Delta. This data collection is primarily looking at water motion and water quality in the bay and delta.
Two gauges were placed at the northern limits of the study area on the Mobile River and the same latitude on the Tensaw River. The southern boundary of gauges is located along the U.S. 98 Causeway at the three major openings for the Tensaw, Apalachee, and Blakely Rivers. There is also a water quality station on the Mobile River co-located with the National Oceanic Atmospheric Administration Port, or NOAAPORT, gauge on the north end of the Alabama State Port Authority Docks. The NOAAPORT broadcast system provides a one-way broadcast communication of NOAA environmental data and information in near real-time to NOAA and external users. These sites measure water level, average stream velocity, turbidity, salinity, water temperature, and suspended sediments.
In addition to the continuously operated gauges, Mobile District team members completed tidal and water-quality sampling at 15 sites throughout the delta.
“The purpose of the data-collection effort is to calibrate computer models to accurately reflect conditions in the bay and delta to provide the information necessary to evaluate potential effects of possible future actions,” said Joe Paine, one of Mobile District’s senior planners.
Other field-data collection completed for the Mobile Harbor GRR includes wetland delineation, seagrass surveys, benthos, fisheries, and oysters.
The Mobile District, in conjunction with ERDC, completed one of the most comprehensive wetland delineations for the Mobile-Tensaw Delta. Over a period of 10 days, the team traveled more than 300 miles through the primary channels and tidal creeks of the Mobile-Tensaw Delta, cataloging species and measuring the density of vegetation. In addition, “teams from ERDC completed seagrass and fisheries surveys in fall 2016 and May 2017,” said Allen. “These data (points) are being used to establish diversity of species within the system as well as delineation of their habitats.”
Results from this work will be a critical factor in characterizing the baseline conditions of the study area. These conditions will be compared to the conditions resulting from proposed channel modifications to determine the potential environmental effects to the system.