Beach Recharge

Beach Recharge, also referred to as beach nourishment or replenishment, describes a process by which sediment (usually sand) lost through longshore drift or erosion is replaced on a beach.

It involves the transport of the nourishment material from one area to the affected area. This process is often expensive depending upon the source (and thus the cost) of the sand.

Source material is normally from offshore dredging but occasionally land sources are available but costs involved are normally prohibitive.

Great care is needed in selecting an appropriate source material and in preventing damage to the source area. The source material grain size and variability is of the utmost importance. A poorly-designed and/or executed beach nourishment project can result in a severely impacted ecosystem, regardless of how much care is taken to deal with the sustainability of the littoral environment.

when recharge is carried out using dredged material, a 10% sediment to water slurry is used which is either pumped t alone a pipe laid from ship to shore or as a free jet (rainbow pumping).

Ship to shore pipeline	rainbow pumping

Once a beach is nourished, it almost always is necessary to regularly renourish it since nourished beaches tend to erode faster than natural beaches.

The economic activity generated through beach tourism may compensate for the cost of both capital and maintenance beach nourishment works, but only in a small number of heavily urbanized areas.

A Beach recharge scheme took place in Swanage Bay, just to the east of the groups' boundary in 2005. During the late 19th and early 20th century it was decided to protect the cliffs from erosion from the sea by building concrete sea walls and promenades which allowed houses to be built on the tops of the cliffs and behind the beaches. Unfortunately this also stopped the natural supply of sand to the beaches causing them to reduce in volume. It was decided that leaving Swanage beach untouched could lead to damages to local properties and roads over the next 50 years amounting to over £35 million. 

As a result during the winter of 2005/2006, 1.1 million cubic metres of sand was dredged from Poole Harbour channels and pumped on to the beaches of Swanage, Poole and Bournemouth to protect them from erosion as part of a £5 million coastal protection project.

20,000 tons of sand, equivalent to 18 million buckets of sand, was dredged from the Swash Channel (entrance to Poole Harbour) and taken by the dredger close to the beach where it was to be deposited.  A 750m long pipeline was used to pump the sand on to the beach.

To assist the sand in being pumped, it was mixed with a considerable amount of water. As the water/sand mixture exits the pipe, the water flows back into the sea leaving the sand behind. The sand was then spread and leveled by bulldozers.

Initially the sand looked darker than that of the current beach but it lightened to a normal colour after exposure to oxygen and daylight.  Within a few weeks, the action of the wind and waves mixed the sand to look more like the existing beach. 

Work was carried out throughout the winter to avoid disruption to the tourist season. As a result the winter work meant the contractors dealt with winter weather as well as difficult tidal conditions. Therefore, work was carried out very early in the morning and quite late at night to take best advantage of the lowest tides.

Although Swanage is discussed here the scheme was part of a much bigger scheme including bournemouth and Poole beaches as well. In excess of 2 million cubic metres of material was dredged by Poole harbour commissioners of which about 1.1million cubic metres was suitable for beach replenishment. Poole beaches received 450,000m3, Bournemouth beaches 600,000m3 and Swanage 90,000m3.

Below is a video of the beach recharge at Bournemouth Beach.