What do groyne measurements show?
Groyne measurement shows the height and how much sediment is being built up on either side of the Groyne. This allowed me to find out whether long shore drift was taking place. From looking at my graph I found out that there was more build up of beach sediment on the west than the east of the groyne.
How far apart are groynes?
three long groynes with spacing equal to 1200 m, i.e. 3 times the length of the groynes. three short groynes with a spacing of 600 m. three short groynes with a spacing of 1200 m.
What is a timber groyne?
Timber groynes are fence-like structures, and can often provide substantial advantages over other forms of groynes. These include the ease with which the level and profile of the groyne may be adapted (by adding or removing planks), ease of maintenance and their appearance.
How do you do a groyne survey?
Methodology
- Using the compass, identify and record the aspect of each side of the groyne, for example the western and eastern side of each groyne.
- Use the meter ruler to measure from the top of the groyne to the surface of the sediment on each side.
- Take digital pictures to illustrate differences in sediment levels.
How is groyne drop measured?
Groyne measurements Use a tape measure to find the height of beach material on either side of a groyne. Measure in at least three heights along the beach profile for each groyne. You can compare a series of groynes along a length of beach. Beach material is higher on one side of the groyne.
How long is a groyne?
The life span of a groyne is around 25 years. They must be replaced periodically to ensure the coastline continues to be protected. The process for removing and replacing each groyne can take up to two months.
Where is there a groyne in the UK?
Groynes are positioned to trap beach material and are most effective on shingle or gravel beaches which is why the Sussex and Kent shores have an abundance. These pictures were taken on the West Sussex stretch between Littlehampton West beach and Middleton-on-Sea beach.
Is a groyne hard or soft engineering?
Groynes are relatively soft hard engineering techniques. They’re low lying wooden walls that extend out to sea. Groynes will remove a lot of the sand that’s present down-drift of the beach which will result in a thinner beach at this area.
What is a groyne and how does it work?
How do groynes work? When waves approach a beach at an angle, they tend to move sediment along the beach. When there is a barrier in the beach, such as a groyne, this captures sand which is moving along a coast and thus builds up a beach.
What does a groyne look like?
Steel groynes most often consist of vertical sheet piles, single or double, with various profiles, located perpendicularly to the shoreline. They are impermeable structures. Experiments have shown that groynes made of single sheet pile walls are not durable, due to corrosion of the material and abrasion by moving sand.
What is the groyne designed to do?
A groyne functions as a physical barrier by intercepting sand moving along the shore. Sand is gradually trapped against the updrift side of the structure, resulting in a wider beach on this “supply-side” of the structure.
How is the length of a groyne determined?
Appropriate choice of shapes, dimensions and location of groynes is crucial for the effectiveness of shore protection. Groyne length is usually related to the mean width of the surf zone and to the longshore spacing in the groyne field. The active length of the groyne increases with increasing wave incidence angle.
How tall do groynes have to be to cause scouring?
Generally, groynes are designed to stick out about h s =0.5-1.0 m above mean sea level (MSL). Groynes that are too high cause wave reflection, resulting in local scouring. Considering the shape in plan view, the groynes can be straight, bent or curved, as well as L-shaped, T-shaped or Y-shaped.
What do you need to know about groynes?
Groynes built of stacked sand- or ground-filled bags should be considered as a short-term protection measure. Some additional protection measures are necessary, especially at the groyne head. A special filter cloth should be used under the bags to reduce settlement in soft bottoms.
What is the life expectancy of a groyne?
A typical wooden groyne has a life expectancy of around 25 years. The groynes in the image are partly of an open costruction, so they allow some water and sediment to pass through them. This takes some of the energy out of the waves whilst completely solid groynes take all the energy out of the waves that strike them.