900 Marshy Cove is outside of the FEMA defined flood zone.
Our need for insurance is optional. The MC Board of Directors has a quotation in hand and is considering insurance. A decision will most likely be made at the next meeting.
For this report, I make no recommendations regarding the need for flood insurance. Just the facts will be presented. You should read this and make up your own mind regarding the risk of flood damage.
Here is measurement data and observations to consider regarding flood risk.
Observations:
The highest
water level that I have seen in Cambridge Creek was just above the marina
finger piers. That occurred
during a Nor'easter on December 21, 2012.
See photographs.
Hurricane
Sandy on October, 2012: the water was even with the tops of the finger piers or a few inches lower than 12/21/2012.
Hurricane Isabel on September 19, 2003, was measured as the highest since the early 1970's. (I haven't been able to find data before 1970 for Cambridge.)
Some charts from NOAA.
MHHW = Mean High-Higher Water Level = "typical highest tide"
The blue lines represent normal lunar predicted tides.
The green lines represent verified measurements.
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December 21, 2012 - 2.64 feet = 32 inches above MHHW
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Hurricane Sandy: October 29, 2012 - 2.49 feet = 30 inches above MHHW
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Hurricane Isabel: September 19, 2003 - 4.14 feet = 49.6 inches above MHHW
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Summary of facts and calculations.
For water to enter 900 Marshy Cove at floor level, the water would have to
rise to 50 inches above MHHW.
- MHHW is 33 inches lower than the bulk head
- The nor'easter of December 21, 2012 shown in the photos was 32 inches above
MHHW.
- Hurricane Isabel reached 49.6 inches above MHHW or 1/2
below our doorway.
- Accuracy of my measurements and NOAA are estimated to be within one
inch.
Conclusion:
- Isabel is the record High Water Level measured by the Cambridge Weather
Station since its installation in 1971.
- It would take another worst case storm for us to experience water entry at
50 inches above MHHW.
- A storm surge of 33 inches would spill over the bulkhead.
- Above 33 to 40 inches, perimeter damage to gardens and surroundings would
occur along with flotsam debris.
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Sea Level Rising?
Yes, It is confirmed that a long term trend has been clearly confirmed by
measurement since the 1940’s. This data from Cambridge shows a steady rise of 3.48 millimeters per year
with a statistically certainty of 95%. 3.48 millimeters equals 0.137 inches. A little more a than an eighth of an
inch.
At this rate, which seems to be continuing, the water level will rise about
one inch every 7 1/2 years. For our purposes today, this is not significant enough to consider.
In fifty years, it may be concerning.
What do you think? Express your opinion at the next board meeting.
