While we can’t predict storms more than about two weeks in advance, we can very accurately predict what the tides will be like hundreds of years in the future. This means that a homeowner can use a simple tide table to predict the days, weeks, and years when their house will be in danger.
One strategy is to purchase a tide table at the beginning of every year and put boxes around all the days when the tides are expected to go over a certain height—basically, any day over the second-highest digit on the tide table, which corresponds to the height of a typical flood tide. When using a Boston-based table, put a box around all the tides that are over 11 feet. If using a tide table for the Aunt Lydia’s Cove area in Chatham, you will want to put a box around every tide that goes over five feet. Those boxes, combined with a simple weather forecast, tell homeowners when their homes will be vulnerable to severe erosion. Additionally, you can go online, find tide tables for each year decades into the future, and repeat the exercise.
How to understand the changing shape of our fragile coastal landscape.
Erosion has been unkind to Cape Cod and the Islands. Over the last seven years, we have witnessed houses swept off beaches or left teetering on the edge of cliffs. On Nantucket, Sankaty Head Lighthouse and the old ‘Sconset summer homes had to be moved back from the edge of eroding hundred-foot bluffs. By 2008, Chatham was losing 10 feet off the end of North Beach every day when the inlet migrated north. North Beach Island eroded at the rate of 80 feet a year, threatening a dozen camps owned by private homeowners and the Cape Cod National Seashore. The east side of Martha’s Vineyard lost about a foot of beach every day and a troublesome new break opened into Katama Bay, disrupting the Chappaquiddick ferry on the Vineyard. Read more…