Having a 50-year career as a professional coastal scientist with the Army Corps of Engineers and US Geological Survey, I have been following the dismal record of the town, state and Corps dealing with erosion of the Sandwich beaches for the past two decades. I concluded in 2001 that the Corps’ jetties were the principal factor in disrupting sand transport to the east and thus causing the widespread erosion of the beaches and dunes at Sandwich and well to the east. I suggested in 2001 to the town that they pursue the Corps’ Section 111 process. That was ignored until recently.
Finally, the town made agreement with the Corps for sand placement to mitigate erosion. I read, however, with disappointment that Massachusetts Coastal Zone Management is objecting to use of the borrow sand due to less-than-ideal grain size and concern about habitat damage. That makes no sense. The sand dredged from the canal and sand impounded by the north jetty have the same glacial source. And CZM has permitted the Corps to dispose of canal sand offshore for years, thus wasting the sand and covering offshore benthic habitat.
Sand dredged from the canal should routinely be placed on the downdrift beaches during every dredging event. As for the grain size mismatch, I wonder how the analyses were done. Clearly, samples from Sandwich beaches are coarser than they would have been prior to the jetties due to erosion of the finer-grain sediment fraction. A program for allowing sand to be used for beach nourishment should be approved. Placement of somewhat smaller grain size is certainly better than allowing continuing erosion; thus the reason for employing sand “overfill” in such cases.
Last, in the longer term, what is needed is emplacement of a permanent sand bypass system to periodically transfer sand east across the canal mouth and thus mitigate the jetty effects in causing erosion. Such a system is used in several places around the United States and world. This situation in Sandwich will become more common for the Massachusetts coast as climate change impacts increase. It is vital that the state CZM takes an active role in permitting responsible actions to mitigate erosion and climate warming impacts
S. Jeffress Williams