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Abstract/ Summary

On April 9-10, 2020, a spring tide combined with a storm surge to flood the upper Machias Bay, including downtown Machias. There is not a gaged water level measurement for the bay, but the combined tide was estimated to be 11.4 feet. This is 8.4 inches above the base flood elevation (BFE). There is supposed to be a 1% chance of water levels reaching BFE in a given year. A 1% storm is called a "100 year" flood – such an event would be expected to happen, on average, once every 100 years. The Machias Bay has had floods within a few inches of BFE multiple times in the last 6 years, and they seem to be increasing in frequency with sea level rise and increased storm frequency and intensity due to climate change. The April 9-10th flood was significantly higher than BFE. These maps model the resultant water level in the upper Machias Bay and downtown Machias, Maine.

It should be noted that this model overestimates the amount of water above the dike, because the water levels didn't get high enough to actually equalize that area with the bay. Efforts were made to remove the effect of wave action, but that is difficult to assess. It is believed that this model overestimates the flooding in the Bluebird and Skywalker's lots. Water was observed right up to the backs of both buildings and partially into both lots, but not to the extent shown. The water on that side comes from storm drains and not directly from the bay, so that slows it down somewhat.



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