Anticipating Significant Water Rise within the Indian River Lagoon

Located within east central Florida, the Indian River Lagoon (IRL) system is comprised of a collection of intracoastal waterways among a connected grouping of three sub-lagoons including the Indian River, the Banana River, and Mosquito Lagoon. It stretches over 150 miles (over 250 km) and extends north to south from Ponce De León Inlet in Volusia County, southward through Brevard, Indian River, Saint Lucie, and Martin Counties, to Jupiter Inlet in Palm Beach County. It is best described as a shallow water estuary of brackish water realizing maritime tidal effects as well as river flow and rainfall runoff sourced from the peninsula’s interior. It generally represents the body of water that separates the local barrier islands from the mainland. Nearly one million people live and work near (or on) the lagoon system. It is the most biodiverse lagoon ecosystem in the Northern Hemisphere. During hurricanes and other high wind situations, the IRL is subject to situational storm surge and coastal flooding which threatens adjacent communities and the sensitive ecosystem. It can also have a serious influence on storm evacuation and preparedness strategies.

Through the NOAA/CSTAR (Collaborative Science Technology, and Applied Research) program, the National Weather Service in Melbourne, FL (NWS/MLB) recently collaborated with researchers at the Florida Institute of Technology (FIT) to understand the physical nature of the IRL and circumstances which may significantly affect observed water levels at different locations within its basin. The intent is to anticipate when water levels might have a significant impact and the extent of potential coastal flooding for places around its shoreline. To this end, forecasters at NWS/MLB are employing several tools devised by FIT. First, a diagnostic nomogram has been tailored for assessing set-up on the IRL in Brevard County defined as the difference in water levels between Titusville (north-end) and Sebastian (south-end). Thresholds of increasing set-up levels prompt more deliberate forecaster actions ranging from notifying local officials of a growing flood concern to the formal issuance of coastal flood watches and warnings for the IRL. Second, GFS-based ensemble plume diagrams are routinely generated to help with projecting plausible outcomes and to offer a relative measure of forecast confidence. The IRL forecast guidance is provided via an FIT-maintained website. This presentation will elaborate on the veracity of the tools and their operational application with examples. Considerations will also be explored for acquiring near real-time high-resolution guidance whenever IRL flooding might be of high impact and specialized decision-support services requested.