New real-time storm surge monitoring network in Mobile Bay, Alabama

In the spring of 2012, NOAA's Center for Operational Oceanographic Products and Services (CO-OPS), in partnership with the Mobile County Commission, established the first of it's kind Mobile Bay Storm Surge Monitoring Network (MBSSMN). The combination of Mobile Bay's long and narrow coastline boundaries, unique bathymetry, mouth opening to the Gulf of Mexico, and extensive tributary network results in a complex hydrodynamic system where water levels can vary significantly in space and time depending on the combined forcing from tides, winds, and pressure that may occur. The task of establishing a storm surge monitoring network involved installation of five new hurricane-hardened water level stations strategically located throughout coastal Mobile County. With permission from the Alabama State Port Authority, this project's data is combined with the data provided by multiple stations in CO-OPS' existing Mobile Physical Oceanographic Real Time System (PORTS)®. This provides stakeholders with a unique offering of spatially densified water level, meteorological, and tidal current data available on the Mobile PORTS® web page. Mobile County now has a total of eight real time water level observatories to provide full data coverage of its coastline from the Mississippi State line to Chickasaw in the Mobile River Delta at the north end of the county. MBSSMN is also the first local storm surge network in the country to have five of its monitoring stations elevated to Category Five modeled storm surge heights, ensuring the collection of data when it is needed most critically. The network will provide data and products that are critical for coastal resource management across the region on an ongoing basis, but most importantly supporting emergency management decisions before and during the passage of the most severe episodic storm events. Due to challenging station requirements and limited infrastructure in key locations, CO-OPS opted to employ remote radar range sensors to measure water level. Utilization of radar gauges for this purpose provided many operational advantages. After several years of testing, this radar sensor is being used operationally for the first time by CO-OPS, with excellent results after its first year of data collection. The first three MBSSMN stations were installed atop state highway bridges in southern Mobile County. This setup was possible due to the radar water level sensor's ability to measure the sea surface remotely from above, with no components in contact with the water column. Installation of the first three stations was completed in July 2011 and the first storm surge event to be captured was during the passage of Tropical Storm Lee in September 2011. The final two stations are elevated four pile structures that were constructed to raise the instrumentation above the maximum modeled Category Five hurricane storm surge height (22–25 feet above NAVD88). This paper will summarize the unique project requirements, committed stakeholder support, inventive problem resolution, and superb data quality that identify the MBSSMN as a template for future collaborative efforts of this type. A summary overview of the water level station designs will be presented along with observations collected during the passage of Tropical Storm Lee and other high wind surge events. Sample water level data that have been collected across the five network stations during storm events provide examples of temporal and spatial variability of a surge event in Mobile Bay.