**2.3 Historical storms**

Two storm events were chosen for this study. The Blizzard of 1978, herein referred to as the 1978 event, was selected for the peak sea levels recorded at

#### **Figure 1.**

*Points of interest in Saco Bay and Casco Bay. In this study, the model domain south of point 17 (Cape Elizabeth) is considered "Saco Bay," while all points north of 17 are considered to be within "Casco Bay." The mesh designed for the Saco-Casco model is shown in the bottom right.*

*Linear and Nonlinear Responses to Northeasters Coupled with Sea Level Rise: A Tale of Two Bays DOI: http://dx.doi.org/10.5772/intechopen.87780*

Portland Station, identified as a 100-year event. The Patriots Day storm, herein referred to as the 2007 event, was chosen for the peak freshwater discharge that occurred following the storm, offering an opportunity to relate the dynamics of river flooding to SLR.

First identified as an extratropical cyclone on February 5, the 1978 event reached a low pressure of 984 mbar as it retrograded from well off the mid-Atlantic coast to Long Island, moving northward toward the New England coastline [17]. On February 7, northeasterly wind gusts of 83 and 92 mph were reported in Boston and Cape Cod, respectively, along with sustained hurricane force winds [17]. The record surge resulting from the cyclone makes it a focal point for this study, as sea level heights reached their 100-year maximum during this event both in Portland, Maine, and in Boston. Specifically looking at Portland, historical archives report 14.17 ft. (equivalent to 4.32 m) above the MLLW as the peak water level ever recorded [4].

The 2007 event was initially reported on April 15 as a low pressure in the southeastern United States before it traveled north along the coastline. NOAA records indicate a barometric low of 972 mbar and wind gusts up to 59 mph over Portland [18]. The Portland Harbor tide gauge reported a peak water level of 13.28 ft. during this event [4]. Rainfall totaled 5.6 inches in Portland, Maine. River flooding was severe with near record levels reported for the Presumpscot River. This provides an effective case study of rainfall vs. snowfall effects on bay responses between this storm and the 1978 event, as icing resulted in decreased river flow following the 1978 event, whereas a surge in freshwater discharge resulted from the precipitation during the 2007 event. The National Weather Service (NWS) Storm Events Database (SED) and the National Centers for Environmental Information (NCEI) database also reported that the Patriots Day storm destroyed two homes due to flooding, and significant flooding was reported along with high levels of coastal erosion along the bays' coastlines.

Northeasterly coastal winds associated with the northeaster events were captured by the NECOFS model simulation (**Figure 2**). The storm window of the 2007 event over the Saco and Casco domain was defined as April 16, 01:00, when the upward climb of observed winds at buoy C0201 exceeded the maximum winds prior to the storm, to April 19, 20:00, when winds dropped below the monthly mean winds for April 2007. The NECOFS output wind fields for April 2007 differed

#### **Figure 2.**

*Wind velocities during February 1978 (a) and April 2007 (b) at buoy C0201. Observed winds, available only for the latter period, are shown in red, while NECOFS-predicted winds are shown in blue. Storm windows are indicated by vertical black lines. The black arrow in the top left of each plot indicates velocity scale.*

significantly in magnitude and direction from buoy observations. At buoy C0201, NECOFS-modeled storm winds were initially directed in nearly the opposite direction from observed winds, with roughly half the speed. Saco River discharge rates increased rapidly from an estimated minimum of ~60 m3 /s to an estimated peak of ~500 m3 /s on April 16 at 22:00 and remained high for the remainder of the month due to spring freshet. For the 1978 event, no such observations were available, so its storm window was defined purely from NECOFS wind output as Feb 6, 12:00, to Feb 8, 16:00, when storm winds rose above the maximum February 1978 winds not associated with the storm.
