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Lincoln County Sea Level Rise – Flood Study

 

Lincoln County Regional Planning Commission

Lincoln County Commission

Maine Geological Survey

Maine Coastal program 

 

This presentation was prepared by the LCRPC under award NOAA CZM NA11NOS4190077 and NA11NOS4190188 to the Maine Coastal Program from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce.  The statements, findings,conclusions,and recommendations are those of the author(s) and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration or the Department of Commerce.

 

 

In 2013 the Lincoln County Regional Planning Commission (LCRPC) and the Maine Geological Survey (MGS) with support from the Maine Coastal Program jointly conducted The Lincoln County Sea Level Rise – Coastal Hazard Study. The purpose of the study was to determine the potential impact of increasing sea level on the county’s 450 miles of tidal shoreline. There is clear evidence that sea level has increased in mid-coast Maine over the past hundred years. There are also strong indications that the rate of increase has accelerated over the past two decades and that sea level will likely continue to increase in the foreseeable future due to environmental factors. What was (is) not known, however, is exactly how much sea level will rise or how it will potentially affect public infrastructure such as roads and culverts or public and private structures.

The 2013 study examined the impact of potential increases in sea level on top of the highest annual tide (HAT), in addition to the "storm of record", which for Lincoln County was the February 1978 storm, which resulted in the highest observed stillwater elevations along the Maine coastline. The storm combined an approximate 3.5 feet of storm surge with astronomically high tides which resulted in the highest observed stillwater elevations along the Maine coastline.  Because this analysis only used effective stillwater elevations and did not include impacts associated with wave set-up and run-up, the predicted inundation associated with sea level rise and the storm of record was considered conservative.

In 2015 FEMA issued new flood insurance rate maps (FIRMS) for Lincoln County, that incorporated wave set-up and run-up on top of stillwater elevation. LCRPC and Lincoln County applied for and funding for the Lincoln County Sea Level Rise – Flood Studyto expand the work completed in 2013 to use this updated data and add sea level rise scenarios to create new inundation data in fourteen of the county’s coastal communities. Peter Slovinsky of the MGS was the principal scientist overseeing both projects with assistance from Bowdoin College Department of Environmental Studies Program and the LCRPC GIS staff. New maps were developed to demonstrate the areas that may be inundated by 1- and 3-foot increases in sea level on top of the 100-year base flood elevations, or BFEs, from the FEMA FIRMS.

It is important to note that the newly mapped data took the effective 100-year base flood elevation data and added 1 and 3 feet of sea level rise, respectively.  No new analyses for potential changes to flood zone types (e.g., an AE-zone becoming a VE-zone) or additional wave run-up or wave set-up calculations were completed.  For example, if an area had an effective AE zone of BFE15 feet NAVD, the new flood zones would simply be AE zones with BFEs of 16 and 18 feet, respectively.   Thus, these results should be used for planning purposes only, and not used to determine potential flood insurance rates.

The results of this study will be presented individually to the coastal communities.  In addition, LCRPC staff has prepared amendments to each coastal community’s flood ordinance that, if enacted, will help protect new construction and major additions to existing structures from predicted increase in sea level. 

In order to view the mapping produced by this work effort, the following links are provided.  For those who already have Google Earth on their computer, click on the Lincoln County link for county-wide mapping or one of the town links to focus on an individual community.  For those who wish to install Google Earth click here

Boothbay
Boothbay Harbor
Bremen
Bristol
Damariscotta
Dresden
Edgecomb
Monhegan
Newcastle
Nobleboro
South Bristol
Southport
Waldoboro
Westport
Wiscasset

The 2013 study examined the impact of potential increases in sea level on top of the highest annual tide (HAT), in addition to the “storm of record”, which for Lincoln County was the February 1978 storm which resulted in the highest observed stillwater elevations along the Maine coastline. The storm combined an approximate 3.5 feet of storm surge with astronomically high tides, which resulted in the highest observed stillwater elevations along the Maine coastline.  Because this analysis the study  only used effective stillwater elevations and  did not include impacts associated with wave set-up and run-up, the predicted inundation associated with sea level rise and the storm of record was considered conservative.In 2015 FEMA issued new flood insurance rate maps (FIRMS) for Lincoln County, which included data layers suitable for incorporating that incorporated wave set-up and run-up on top of stillwater levels into the sea level rise model.  LCRPC and Lincoln County applied for and funding for the Lincoln County Sea Level Rise – Flood Study to expand the work completed in 2013 to use this updated data and add sea level rise scenarios to create new inundation data  include wave set-up and run-up in fourteen of the county’s coastal communities. Peter Slovinsky of the MGS was the principal scientist overseeing both projects with assistance from Bowdoin College Department of Environmental Studies Program and the LCRPC GIS staff.   Using the newly issued FEMA 1% storm layer, New maps were developed to demonstrate the areas predicted to that may be inundated by 1- and 3-foot increases in sea level on top of the 100-year base flood elevations, or BFEs, from the FEMA FIRMS.