Storm Surge and High Tide Relationships in the Delaware Inland Bays

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It has been widely documented that Delaware is highly vulnerable to the impacts of coastal flooding along its Delaware Bay, Atlantic Ocean, and Delaware Inland Bay shores. This is due to surge from coastal storms as well as astronomical high tides, which are both predicted to get worse as relative mean sea levels increase due to climate change. Delaware’s coastal regions contain large areas of low, open, flat coastal terrain, where small vertical changes in water levels result in large horizontal extent of flooding, with growing residential and commercial development and critical natural resources within or adjacent to these coastal regions. The entire mid-Atlantic region is susceptible to both tropical storms in the summer/fall and extratropical storms in the winter/spring. As well, the region resides in a hotspot of relative sea-level rise due to subsiding land surface and rising seas. Hence, coastal flooding is a real threat to the region, and was ranked as the top risk hazard in statewide across Delaware, with loss of life and damages done to the natural and built-up environment likely the most significant natural hazard facing Delaware today.

This project will focus on the Delaware Inland Bays (consisting of Rehoboth Bay, Indian River Bay, and Little Assawoman Bay), an area which has undergone rapid change in development and landuse in recent years and has experienced significant impacts of storm surge and high tide coastal flooding. All of the Bays, tributaries, and ditched and unditched marsh wetlands in this region are complex hyrologically and tidally connected to each other, making hydrodynamic predictions difficult.

Tidal water levels in the DIB have been monitored for almost 20 years, although only at a limited number of sites, by the USGS (5 sites) and NOAA (2 sites.) Recent research projects (including this one) have added 10-15 additional monitoring sites for a temporary time period, primarily maintained by the UD Center for Environmental Monitoring and Analysis (http://www.cema.udel.edu/). DGS and UD CEMA will work together to continue to collect tidal data in the DIB through early 2020 and analyze this data for relationships of coastal flooding throughout the region. In particular, the timing and severity of high tides, and meteorological drivers (wind speed, atmospheric surface pressure, precipitation) will be investigated. It is the hope that results of this work will result in better understanding of the complex hydrodynamics of the region and support application of a coastal flooding early warning system for DIB communities.