Sills are an erosion protection measure that combines elements of both revetments and offshore breakwaters that are usually made of stone and are built close to the shore. Typically, they have the same triangular cross-section as breakwaters but tend to be smaller in size and are continuous (Hardaway et al., 1999).

 

Sills are a combination of harder shoreline structures with the use of other natural elements, which allows them to be classified as a living shoreline. This creates a natural buffer which can preserve or create habitats between the rock line and the shoreline, which may increase aquatic life and boost mussel populations.

 

Sills can also be designed to fit irregularly shaped areas such as gaps to provide for wildlife or recreational uses. Marsh fringes are usually placed behind the sills to allow for higher energy situations (Hardaway et al., 1999). This could require more maintenance and periodic replanting.

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Decision Matrices Results:

 

Dublin Hollow site: 2.61 / 5.0

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Dam site: 3.26 / 5.0

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Pros:

1.  Long life span

2. Good habitat potential

3. Optimal wave protection

at the Dam site