Flooding Redux – Or – “I have never seen water why am I in a flood zone?”

“I have never seen water why am I in a flood zone?”

A question we have heard often over the past year or more. Repeatedly we have told callers that the Cape has not seen a 1% storm in many years, in fact, the closest would be 1954 when the region experienced two hurricanes in short succession.

Often I have mentioned that Hurricane Edna most closely matches a 1% storm in our region. Hurricane Edna produced a 6 foot storm surge over much of Cape Cod. A six foot surge, at high tide, pushes water to, roughly, ground elevation 12.

Looking at the land area southeast of Swan Pond, Hurricane Edna pushed water into much of the area covered by a 1% storm. Pushing water through the cottage colonies and the Plashes to the southern edges of Dennis Port Village Center. At the same time, waters from the Swan River flow through the wetlands between Route 28 and Upper County Road, reaching the westerly edges of the village in the area of the Dennis Port Post Office.

6 foot surge

 

Edna was not the strongest storm ever experienced on the Cape, nor the highest storm surge. However, it provides the closest match for discussing the impacts of a 1% storm.

Earlier in 1954 Hurricane Carol struck parts of the Cape with a larger surge (New Bedford Harbor recorded a 20 foot storm tide) even as it happened just after high tide. The Hurricane of 1938 is also documented as having larger impacts, if not the largest impacts ever, on Cape Cod.

Anecdotal information tells us that the Great Atlantic Hurricane of 1944 had the largest storm surge impact of any past storm on Dennis – even though, according to the September 1944 Monthly Weather Review, it hit at low tide.

So, if your property is in the red areas on the map above, your property probably experienced some level of flooding in 1954, 1944 and 1938.

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