Analysis of Storm Surge and Tidal Data Relationships in the Delaware Inland Bays based on Meteorological Conditions

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In the U.S. Mid-Atlantic and Northeastern states, both tropical systems and extra-tropical storms (particularly nor’easters) frequently cause significant loss of life, injuries and property damages reaching many billions of dollars. Delaware has been significantly affected by many great storms throughout its history, particularly the Hurricane of October 1878, Ash Wednesday storm in March of 1962, the Mother’s Day storm in May of 2008, and most recently Hurricane Sandy in October of 2012. Although coastal events bring many types of natural hazards (beach and dune erosion, winds, waves, precipitation) and public infrastructure damage (powers loss, road damages), storm surge is a leading cause of coastal inundation and often the greatest threat to life and property from a tropical or extra-tropical storm. Additionally, Delaware falls within a “hot spot” of relative sea level rise due to both eustatic (global sea level rise) and isostatic (land subsidence) processes with local SLR rates nearly double to global rate of 1.7 mm/year. The Delaware Inland Bays, comprised of the Rehoboth Bay and Indian River Bay, are a primary concern due to direct connection to the Atlantic Ocean through Indian River Inlet, population and development along the Bays’ coasts, and low-lying elevation.

In response to Delaware’s concern of sea-level rise, frequency and intensity of meteorological events, susceptibility to high tides and storm surge, and increasing community population along the coast, the Delaware Environmental Observing System (DEOS) and Delaware Geological Survey (DGS), with support and funding from DNREC Delaware Coastal Programs (DCP), developed the Delaware Coastal Flooding Monitoring System (CFMS). (More information on the Delaware CFMS can be found here.) Unfortunately, the Delaware Inland Bays are not included in the current implementation of the Delaware CFMS. Because of the complex hydrology of the Inland Bay system, the modeling approach used in the CFMS for the Delaware Bay and River coastline cannot be used for the Inland Bays.

This project will study the water level behavior throughout the Delaware Inland Bays, with a focus on populated areas, during times of both storm and non-storm events through analysis of observational data from tide gages. It will also support the inclusion of the Delaware Inland Bays into the Delaware CFMS by developing a statistical relationships between the water levels along the Atlantic Ocean coast near the mouth of the Inland Bays system and those observed within the Inland Bays based on varying weather conditions. Water level data from both USGS and National Ocean Service (NOS) tide gages as well as data from state, federal and other sources will be collected and merged into a common vertical datum, such as NAVD88 meters, and reviewed for quality control. New sensors will be installed within the Inland Bays where sparse data coverage exists. Harmonic analysis then will be performed to separate the astronomical tide from the non-tidal, meteorological residuals, with these data then being used for developing the statistical relationships. The statistical analysis will include a breakdown based on meteorological conditions, particularly wind and type of flooding caused from (sub-tidal) storm events. Meteorological data will be provided by National Weather Service (NWS) and Delaware Environmental Observing System (DEOS) meteorological stations. The results of the project can facilitate the inclusion of the Inland Bays into the Delaware CFMS in order to provide an early warning and monitoring system for those communities. This information will assist emergency managers and local officials to prepare for impending flooding events.