Storm Tide Pathways: A Collaborative Effort to Mitigate the Impacts of Coastal Flooding

Coastal flooding along the eastern Massachusetts coastline has become a more frequent occurrence in the context of sea level rise over the past several years. Flooding occurs from the combination of tide and storm surge (referred to as total water level) and damage is exacerbated by wave action on top of the surge. The more significant events, which can cause structural damage, are often associated with strong coastal storms such as nor’easters but even minor impacts do occur during high astronomical tides when no storm is present.

For decades, the National Weather Service (NWS) has issued Coastal Flood Watches, Warnings, and Advisories in a text-based format to inform decision makers and the public of coastal flooding. These products cover long reaches of coastline with limited specificity. Over the past several years, the NWS Weather Forecast Office (WFO) in Boston/Norton, MA has produced gridded forecasts of total water level and more recently integrated Geographic Information System (GIS) technology to highlight specific areas at risk through visualization.

Storm tide pathways, by virtue of their elevation relative to the elevation of a storm tide, provide a direct hydraulic connection between coastal waters and low lying inland areas. Examples of pathways that can carry elevated coastal waters inland include low spots in the built environment (e.g., roads, walkways, dikes, and seawalls) and low spots in natural topography (e.g. low lying earthen berms, barrier beaches, and dune systems susceptible to erosion and breaching). Using state-of-the-art Lidar information and GPS technology, the Center for Coastal Studies (CCS) identifies and maps current storm tide pathways and those that may function as pathways in the future. When integrated with WFO Boston/Norton’s inundation mapping of total water level forecasts, the storm tide pathway information can be used by emergency managers to prepare for coastal flooding events and to plan for future improvements.

This presentation will describe the NWS forecast process and show the methods used by CCS to develop Storm Tide Pathways for a community. Examples of how the information has been used by officials in Provincetown, Massachusetts to mitigate flood impacts will be shown in order to demonstrate the utility for other communities that are affected by coastal flooding.