|
|
Bournemouth Beach
Top-up (BIS4.4) March 2009
 The
replenishment of a
section of beach at Southbourne by the Fareham-based
Westminster
Dredging Company, using the Dutch dredger Crestway.
The Crestway made her first
delivery to the beach on Wednesday 4th March 2009.
BIS4.4 was
completed on Saturday 21st March, with 74,192 cubic metres added to the
beach between Groynes 50 & 53.
Beach material was dredged off the
Isle of Wight and brought close to the beach by the dredger from where it
was pumped ashore through a 300m long floating pipeline and then levelled
by bulldozers.
The dredge/sail/discharge cycle
from the IoW took approximately 11 hours.
100% Grant Aid
funding was received for this project from The Environment Agency on behalf of Defra
(the government Department for Environment, Food and Rural Affairs).
The Beach Material
The dredging
area off the Isle of Wight was selected because the material there is
so similar to the natural beach material at Bournemouth, and is within
economical reach for the dredger.
The material
is a sand & shingle mix (predominantly sand). The coarser
material is needed to ensure the beach is not washed away, and it is
possible that, from time to time, it will naturally rise to the surface,
particularly at more exposed areas in the east of the bay.
Further Work
One more top
up is planned for 2010; the exact date and location will be confirmed much
closer to the time
The existing
timber groynes 51 and 52 are life expired and will shortly be rebuilt,
using the replenished beach as a working platform.
Contact
Dr David Harlow
Coast Protection Manager
Bournemouth Borough Council
Town Hall Annexe
St Stephens Road
Bournemouth BH2 6EA
Tel: 01202 451389
Fax: 01202 451008
Email David Harlow
|
 |
For more detailed
replenishment process information and pictures see
BIS4.1 (opens in a new window). |
|
About
Beach Improvement Schemes
During the 20th Century, the cliffs were protected from coastal
erosion by building concrete seawalls and groynes. This allowed houses and
roads to be built on the cliff tops, but it also stopped the natural
supply of sand and gravel to the shore. So beach material that is
lost to natural coastal processes cannot be replaced by any other than
artificial means.
Bournemouth beach loses approximately 70,000 m3 of material annually (1 million m3 every 13 years.
Since the predominant direction of longshore
transport in Poole Bay is from west to east, sand gradually feeds
the beaches at Southbourne and Hengistbury Head to the east, and
beyond into Christchurch Bay.
The
shoreline has been
replenished on several occasions in recent years; these projects are referred to as 'Beach
Improvement Schemes' (BIS):
|
Scheme |
Year |
Quantity of Sand (m3) |
|
BIS1 |
1970 |
84,000 |
|
BIS2 |
1974/75 |
1,400,000 |
|
BIS3 |
1988/89 |
1,000,000 |
|
BIS4.1 |
2005/06 |
600,000 |
|
BIS4.2 |
2006/07 |
898,000* |
|
BIS4.3 |
2008 |
70,000 |
|
BIS4.4 |
2009 |
70,000 |
|
*included 15,000m3 stockpiled for the
Boscombe
surf reef |
|
In the past Bournemouth Council has carried out
"boom & bust" replenishment schemes, where the beach is delivered
with a large quantity of material (e.g. 1974/75) and left until much
of it is lost before further replenishment (e.g. 1988/89).
The first stage of Beach Improvement
Scheme 4 (BIS4.1, 2005/06) was
part of a wider scheme that included the replenishment of beaches at
Swanage and Poole using sand dredged from Poole Harbour. The
project continued at Bournemouth during the winter of 2006/2007, between Boscombe and Alum Chine, using a further
supply of sand from a Licensed Dredging Area off the Isle of Wight
[BIS4.2].
During the three years 2008-2010 the council pledged to make good the
annual losses to keep the beach at a constant level and volume
(BIS4.3, BIS4.4 and
BIS4.5).
Replenishment is localised and takes just a few days.
It is undertaken during winter
months in order to minimise disturbance to public access &
enjoyment. |
|
|
