Southwest Ameland Climate Buffer
The mudflats and sandflats on the southwest side of the island of Ameland are bordered by a deep channel. These mudflats and sandflats have been eroding for more than a hundred years. The erosion is caused by the shifting location of the deep channel and the loss of shell deposits that used to form a buffer. The dams, mudflats, and sandflats complex may come under pressure if the channel should continue to shift eastwards. These dynamics are affected by a range of factors.
Results
The southwest Ameland Climate Buffer involves an implementation-oriented experiment with natural processes, such as the formation of shellfish deposits, and the extent to which these could constitute a buffer to the mudflats and sandflats southeast of Ameland. In the past, solid flood defences have been used, such as a rockfill parallel dam and a wicker dam. East of the rockfill parallel dam, a sandflat has developed, with a shell deposit immediately adjacent to the sea wall, along the old “Feugelpôlle” sandflat. This shell deposit is a good breeding habitat for many coastal birds and is well-known for its large colony of Sandwich terns.
As yet, data on the function of sandflats in relation to coastal safety and natural processes is insufficient. The southwest side of Ameland, along the deep channel, is one of the locations that can be properly monitored, in order to gain experience with practical experiments.
Conducting experiments improves the potential for anticipating future changes to the climate. The implementation measures are:
1. Building up a clay shell supply to protect the Feugelpôlle sandflat.
2. Re-introducing a shellfish deposit (mussels) on the Vrijheidsplaat sandflat.
3. Maintenance of the existing wicker dam in the Westerkwelder mudflat.
Sub-project 1 comprises depositing a clay shell buffer on the borders of the existing Feugelpôlle, and constructing wicker dams to counteract erosion on the west side, while slowing down and reducing further deterioration of the remaining mudflat. The most recent shells were deposited here in August 2013.
Sub-project 2 focuses on the long-term restoration of the natural formation of shellfish deposits along the deep channel on the Vrijheidsplaat sandflat. As a result of overfishing in the entire Wadden region, tidal mussel beds have all but disappeared south of Ameland. The experience gained in the Waddensleutels research project will be used in the restoration of a mussel bed on the Vrijheidsplaat sandflat along the deep channel. The initial aim of introducing live mussels turned out to be quite complicated in terms of permits. For that reason, further considerations resulted in the choice of biodegradable crates without live mussels (see photo). The University of Groningen has had positive experiences with this method. The crates should eventually lead to the development of a live mussel bed, because they provide a good adhesive surface for the breeding of mussels. This fosters the formation of a mussel bed, cockle bed, or oyster bed. The bank of mussel crates, interspaced with coconut matting, was constructed in the spring of 2014. From this bank, sediment could grow on the mudflat. In the past, the current location has seen some mussel beds at a slightly greater distance, but these had all but disappeared in the 1990s.
The chances of success are unknown. An additional option is introducing dead oyster shell material, provided this is available. The presence of mussels breeding in the vicinity is demonstrated by the quite recent attachment of mussels to the rockfill dam near the locations.
Sub-project 3 pertains to the maintenance of the existing wicker dam in the Westerkwelder mudflat. The dam affects the physical conditions, causing local changes in the supply and transport of sand, sludge, and shells. Screening of the Westerkwelder mudflat with two wicker dams between the dyke and the rockfill dam is intended to create peaceful conditions. This will promote the deposit of (fine) sediment on the Westerkwelder mudflat.
The film below shows the process and the first interim results of the Zuidwest Ameland climate buffer.
At the end of 2014, the Zuidwest Ameland project was completed and its results were incorporated into this brochure.