4/13/1978 CONSERVATION COMMISSION Minutes

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.� ar MASHPEE CONSERVATION CMUSSIONSPECIAL 14EETING DATE: April l ., 1978 Mashpee Town Hall TIME: 7:30 . e special meeting was called by Acting Chairperson Pauline DeL ry, with the following members in attendance: Barbara Sloane, Charles Buckingham and Norman Dias. Andy Guttman, of MIT, had been invited to give a slide pre- sentation and to make comments on the perched beach concept. During the- showing of slides., his comments included the following Erosion varies 6 to 101 per year - groins are used to stop erosion, but the problem is that 't causes detrimental effects on property owners with the "down drift". Another form of erosion control. is -the sea wall - concrete i and wooden bulkhead. Another type is the stone mound - large boulders placed on the beach. Beach nourishment is another type - protecting pro- perty inland during storms. He also said that low-cost erosion control is appropriate for bays and estuaries, but is not suitable for areas such as Nauset Beach - would not be suitable for Forth Truro with the huge eaves during the winter. With the perched beach, bags get placed between mean high water and mean low water. It is a cycle - sand being drawn away from beach in the winter and brought back in the summer - they are placed parallel to the shoreline - sand comes from on-shore sediment transport. Another concept is the sand grabber, which is made of concrete - it i very dangerous -- the sand bags are soft. In one case where the sand grabber was employed, two months later the entire structure was destroyed during the big storm. It is not a propriate for high wave energy environment. Also., the sand grabber can break apart easier than the sand bag. sump pump is used to fill the bags with a sand and water mixture - the water escapes through the holes in the bag, leaving the sand behind. He said they are currently in use at Dennis, Morris Island and Bay Road Beach and others are being planned. The perched beach was started at Dead Deck Island in August of 1977 and it did not work - no sand to accumulate where here 'isn't enough sediment transport. It was used at Bay Road, Eastham and three weeks later, the bags were almost covered - you get a Crider beach from it - only about 1 or 12" . If a higher bag was used., here would be a much�more significant perch. He mentioned Morris is Island in Chatham - he also said the best time to pint it in is in the spring for the best accumulation of sand. Morris Island includes 10001 beach owned by the Wildlife Refuge -- in November they put in sill bags the sand that was eroded from the dyne was caught by the perch. It was put in in November rather than the spring and they will have to wait until next fail to see what is going onf He also said that the bags will never have any effect in controlling erosion caused by storms like the one in February. she bags would probably function well during a mild store but not in a 'huge nor .l easter. He added that all these pro- jects so far are experimental - he's monitoring thea now, In Chesapeake Bad` the concept has worked well - rather than going straight across the level of the beach, the perch is following the original proffille of the beach - due to the differencein the tide range., they don't know If it works real we'-.1 in Massachusetts. The bags don't have a very long life if not covered with sand -- they could break - they are not a permanent structure - they have a limited life span and are subject to van- dalism. He also said that the bags we ren't damaged by ice, i