Coastal Flooding and Erosion Forecast

NERACOOS has worked with meteorologists at the National Weather Service in Gray, Maine to prototype a decision-support tool for NERACOOS that predicts coastal storm damage. The tool uses forecasts of water level and waves to predict coastal damage near Saco, Maine. A prototype was recently adapted to Scituate, Massachusetts and is being validated with storm data from the weather service and local emergency management community.

The Coastal Flooding and Erosion Forecast is now available in real-time for the following locations:

How does it work?

An empirical relationship exists between storm tide, waves and coastal flooding or splash-over damage which allow us to predict when flooding and splash-over events (such as beach erosion) might occur based on forecast water level (tide height) and wave height data.

  • The red line (horizontal) represents the point at which the water level is at flood stage (FS).
  • A yellow line (slight diagonal left to right) represents when splash over begins.
  • Progressively darkening horizontal bands (light orange to red), represents when minor, moderate and severe coastal flooding will occur.

When the nomgram is in motion, a real-time indicator moves through the 48 hour forecast as a series of red circles. The leading circle of the indicator represents the most recent reading, and the trailing circles are previous readings (in 1 hour increments).

These retrospective animations from three historic storms show the tool in action for Saco, ME:

Saco road erosion

St. Patrick's Day Storm
March 16-17, 2007

  • High waves caused significant erosion due to splash over
  • Forecast predicted days in advance there was a high likelihood of this happening


St Pats Storm

Saco Storm

Patriot's Day Nor'easter
April 15-17, 2007

  • Four high tide cycles with waves greater than 20’
  • Combination caused tremendous damage during the storm
  • Forecast predicted days in advance there was a high likelihood of this happening

Patriot's Day Storm


Low Water

Just another Storm
November 15-16, 2008

While not a forecast to be a significant event, this storm showed the value of the forecast tool for predicting coastal flooding.

  • Forecast was for a high water level event, with minimal waves - coastal flooding
  • Nomogram showed minimal splashover
  • Targeted forecast to low-lying areas that would be impacted by high water level
Nov 15 08