HARPSWELL — An environmental consultant told the town he could find “absolutely no justification” for the flood lines drawn in the preliminary flood hazard maps released in April by the Federal Emergency Management Agency.

Selectmen met with consultant Nate Dill of Ransom Consulting Wednesday afternoon to discuss appealing the maps. If they decide to go forward, the town could join an appeal with a handful of other towns in Cumberland and York counties.

The maps will affect insurance rates for property owners within the redrawn lines; an area proposed by the new maps significantly expands the flood hazard in Harpswell, which has 216 miles of coastline.

Based on his review of the town, Dill said the analysis generalized areas of the coastline, and drew lines “with too broad a brush.”

He also argued the data is not as accurate as it could be.

He attributed the imprecision to FEMA’s data collection models. In the last 10 years, the agency altered its model to calculate flood zones by factoring not just the average sea level elevation, but also the “wave setup” – the water that accumulates above sea level onshore after a wave crashes against a coastal feature or structure.

The change took effect after Hurricane Katrina in 2005 devastated New Orleans, where coverage areas did not properly account for wave setup, Dill said.

However, Dill said the model isn’t as appropriate in New England, and described it as “overly conservative.”

If Harpswell hires Ransom, he said, the consulting firm would apply more modernized, advanced models to calculate Harpswell’s flood hazard zone.

To do that, he said, the firm needs to study all of Casco Bay. That is part of the reason why he is advocating for York and Cumberland counties to file a joint appeal; he added that an appeal from an entire county or multiple counties would strengthen the case.

The town will have 90 days to appeal the maps after FEMA announces the appeal period; Dill said he believes it will begin in late summer.

With time running out, he said he needs to hear from Harpswell and surrounding towns by the end of July about whether they will join the appeal.

Harpswell would be the fifth town to join, although selectmen Wednesday expressed their intention to urge other towns in the county to get on board for the effort. Not only would it bring costs down, they said, but the data should theoretically benefit the other towns, too.

The analysis will cost $210,000, divided evenly among the number of participating towns. Town Administrator Kristi Eiane said Harpswell has a budget of $55,000.

Dill repeatedly emphasized that the lines impact the entire town by spurring a cascading effect where the insurance premiums drive up property values along the coast, which can affect the overall tax rate.

“Everyone lives on the shore here,” Selectman David Chipman said.

Since the 1970s, Harpswell has collectively paid about $180,000 in flood insurance premiums annually, Eiane said. But in that time, only 32 claims were paid, totaling about $60,000.

Based on that data, Dill echoed selectmen in surmising that the risk of flooding in Harpswell, even with its vast coastline, has been overestimated for years.

Callie Ferguson can be reached at 781-3661, ext. 100, or cferguson@theforecaster.net. Follow Callie on Twitter: @calliecferguson.

Edited 7/21: To remove paragraph that mistakenly stated the number of property owners affected by the proposed new floodmaps.

Harpswell Selectmen David Chipman, left, Rick Daniel, and Kevin Johnson discuss with a consultant on July 19 whether the town will appeal updated flood plain hazard maps released by the Federal Emergency Management Agency.