Brazos Santiago Pass Hydrographic Surveys 2012-2013

Project Description

Larry Lloyd
Research Specialist II

From 2000 to 2005, an annual average of over 1.5 million metric tons of liquid petroleum was handled by the Port of Brownsville as waterborne cargo transported through the Brazos Santiago Pass and the Gulf Intracoastal Waterway (GIWW). Hydrodynamic and oil spill models are available for most Texas Bay systems that assist oil spill responders in determining the most effective early response strategies to mitigate the harmful effects of an oil spill. A need for data to create and validate predictive hydrodynamic models to prepare for the possible event of an oil spill for the lower Laguna Madre was identified. Additionally, surface currents, 3D currents and bathymetric data will also help assist marine scientists better understand the water exchange volumes of the lower Laguna Madre and the Gulf of Mexico and will serve as a tool to assist barge captains with safe navigation.  A Coastal Impact Assistance Program (CIAP) grant was awarded to Cameron County to gather the data needed for models, navigation and oil spill planning. Cameron County commissioned the University of Texas Pan-American (UTPA) Coastal Studies Lab (CSL) and the Conrad Blucher Institute for Surveying and Science (CBI) at Texas A&M University – Corpus Christi (TAMUCC) to conduct hydrographic surveys of the Brazos Santiago Pass and surrounding inlets, disseminate the data to the public, and create maps that will visually summarize the data. The data gathered was intended to establish a baseline to which future data can be compared.

Project Methods

Twenty one hydrographic surveys of the Brazos Santiago Pass and surrounding inlets were conducted from November 16th, 2012 to November 13th, 2013. A Sontek RiverSurveyor M9 acoustic Doppler current profiler with GPS was outfitted on a boat to collect survey data. The RiverSurveyor and GPS were interfaced to collect a sample every second consisting of 3D water velocity, water depth and GPS coordinates. Transects were repeated once during each survey day in the same areas: Port Isabel Harbor, South Bay inlet, Brownsville Ship Channel, Tompkins Channel, and the along the Queen Isabella causeway. Additionally, several surveys of the mouth of the Brazos Santiago pass were conducted at the beginning and again at the end of each survey. The transects were chosen so that every single area of water exchange were surveyed to gather data on total water inflow and outflows of the section of the lower Laguna Madre most likely to experience an oil spill from a transportation barge or be effected from an offshore oil spill. Surveys were conducted during different water level and wind regimes to gather data from as many natural scenarios as possible. Water level, wind speed, wind gusts and wind direction data were gathered from a local Texas Coastal Ocean Observation Network (TCOON) located at the South Padre Coast Guard Station (26.072474°, -97.166835°). All data were recorded internally on the RiverSurvey during the surveys and then downloaded and stored internally after each survey was completed. Binary files for each survey were converted to ASCII text files and complied in a spreadsheet that was imported into ArcMap to create maps to visually summarize the data. Separate maps were created for water depth and surface water currents to show all transects completed during each survey. Maps, spreadsheets and raw comma delimited ASCII is available for download on CBI’s webpage:

All maps were created by Paul van Oldenmark.

BSP survey_121116_bathymetery overview

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