LACONIA — The recommendations of the Woods Hole Group for stemming the erosion and restoring the extent of Weirs Beach will be presented to the City Council when it meets Monday night.
Under contract by the city, the Massachusetts consulting group began studying the migration of sand at the beach in 2011 and in 2012 reported that each year approximately 1,200-cubic-yards of sand — enough to fill 182 city dump trucks — is swept by wind and water from Weirs Beach into Lake Winnipesaukee and the Weirs Channel.
The team from Woods Hole Group collected data on the direction and strength of prevailing winds and waves, along with records of water levels and measures of water depth. Meanwhile, a crew from the Department of Public Works regularly surveyed the beach over the course of a year to provide a record of its changing topography. He said that analyzing and modeling this data indicated that some 600-cubic-yards of sand was blown from beach by wind, another 500-cubic-yards was lost to the action of waves and less than 100-cubic-yards was carried away by stormwater. The total of 1,200-cubic-yards calculated by the model nearly matched the 1,275-cubic-yards confirmed by the surveys of the beach.
In its final report the Woods Hole Group recommends a handful of measures to mitigate the erosion and stabilize the beach. First and foremost, the report calls for "nourishing" the beach with between 7,300 and 9,000-cubic-yards of additional sand, which would increase the width of the beach by 60 to 75 feet,
The report proposes supplementing the addition of sand with steps to keep it in place. First, installation of sand fence parallel to the jetty at the eastern edge of the beach would capture sand that wind would otherwise sweep into the channel. The group estimates the fencing could trap as much as 600-cubic-yards of sand a year, which is equivalent to the annual loss of sand to the wind. Fencing would be accompanied by what the report calls "manual backpassing", or simply transporting the sand captured at the eastern edge of the beach to the western end of the beach every two or three years. Finally, adding 20 feet to the jetty, which reaches about 100 feet into the lake, would significantly reduce the amount of sand carried around the jetty and into the mouth of the channel.
Finally, the report suggests erecting two adjustable barriers called groins to stabilize the replenished beach would extend the life of the restored beach. The authors of the report estimate that after five years only half the additional sand would remain without the groins compared to three-quarters of the additional sand with the groins. After 25 years only a quarter of the additional sand would remain without the groins compared to nearly half with them.
The estimated cost of the five recommended measures ranges from $438,000 to $576,000, with the cost of adding sand to beach representing the largest single cost at $200,000 to $300,000.
Weirs Beach is not a natural beach, but was built between 1950 and 1960 with sand dredged from the nearby channel and trucked from Gilford. The beach was built in three stages, the northern section first, then the southern section and finally the middle section between, which was bounded by two jetties, or groins, fashioned of iron rails, railroad ties, rocks and sandbags. A third jetty was built along the channel.
By 1958 erosion had already taken its toll, washing away some 2,000-cubic-yards of sand. Although the sand was restored, erosion persisted, shaping a scalloped shoreline framed by the jetties. In 1975 a study concluded that the fine sand could not withstand stormwater and wave action and recommended removing the jetties, raising the elevation of the beach, improving the surrounding drainage and rebuilding the jetty lining the channel. Despite these steps, the beach continued to migrate, forming the crescent there today.
For years business owners at The Weirs longed to restore the beach, but were discouraged by the lack of sufficient funds and the stringency of environmental regulation. Nevertheless, in 2000 the city dedicated revenues from parking in excess of $25,000 a year for "dredging and reconstructing Endicott Rock Park Beach" and five years later created a "beach refurbishment fund," supported by beach fees, which has a balance of some $68,000.
After the boardwalk was damaged by a flash flood in August 2008 the Weirs Action Committee (WAC) suggested restoring the beach along with rebuilding the boardwalk, but the two projects could not be undertaken at once. However, in November 2009 the WAC voted to ask the city to address erosion of the beach and the following spring Robert Ames and Joe Driscoll of the WAC, together with Dunleavy and Luke Powell of the Department of Public, met with officials at DES.
Officials of the DES recognized the importance of the beach, both to the tourist economy of the city and the region and as a major source of public access to Lake Winnipesaukee. Moreover, the Army Corps of Engineers has assured city officials that the agency would not intervene on a project of three acres or less, but instead would follow the recommendations of DES.
Encouraged by the response, the city contracted with the Woods Hole Group in May, 2011 to undertake the study of the beach.
The completed study has been forwarded to DES for review and comment.