3/23/1978 CONSERVATION COMMISSION Minutes

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or The Cape Coddr t`-' . 1 i 1-Fred ay,Jd d •I 0;01-971j! ge F BgO thes M imr - ed� ays.A.`V,�. .B Old�lj SCn S db gToN' CoHect cr� f The idea behind the "'perched"' beach is to raise and and the entire face of the beach is elevated—hence the intain the level of an eroding beach above-what it term "perched" beach. uld be normally. This .is done by' installing, The higher, wider backshore allows more room for rallel to the shore and usually at the mean low water the dissipation of wave energy. The reservoir sand e, a long, low embankment called a sill. behind a sill protects shoreline structures during st.or- After in tall tion of a sill the beach v it fills-in ms, in 'the same way a non-ero-ding natural beach th sand suspended in the sea water that isw shed would. er the sill by v ind-g'enerat d waves. Sand washed away by' a storm quickly builds u The water dribbles back o the sea 'through the sill 'again behind the sill, protecting the shore from the t the sand is,left behind. The result is that the width next storm. the backshore of the beach increase's significantly For the last four years, Dr. Robert Byrne and Gary, i b ' f Page Five '' � Perched—Continued tors and none have so far been dislodged by ware ac- lion. -tion. If the Dural-bags can withstand wind'and waves on the Cape that are more severe than on Chesapeake 4 Bay, there is still the problem of winter ice to contend 5 with. However, both Dr. Byrne and Dr. Connor still feel the bugs are likely to be successful he' But both men said an important condition to the successful use of sills- is proper placement on the � • F beach. The hags are usually placed near men low 4 { tide, but because of Cape Cod Bay's extensive low tide. flats, the bags will have to be placed closer to the high title line, near or at the Knee of the beach — the point , where.the slope of the beach changes and wet-sand merges with dry sand. - j The precise placement of the bags will depend also ; on the special character of individual leaches. s lf•the Sea Grant experiment with the bags ,is suc- cessful, -eessful, r. Connor said, it may eventually mean a savings of millions of dollars for the bayside residents f Cape Cock.