amenity2
Joined: 10 Jul 2008
Posts: 798
Location: Dovercourt
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 Posted: Sun Feb 22, 2009 8:01 pm Post subject: |
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Got this today, if erosion is of interest to you this might be it?
REVIEW OF UK MARINE AGGREGATE EXTRACTION ACTIVITIES from The Crown Estate and BMAPA showing historic
patterns of marine aggregate extraction in metric tonnes for 2000 - 2005, excluding beach replenishment and fill contracts.
EXTRACTION AREA 2000 2001 2002 2003 2004 2005 Total
HUMBER 3,122,080 2,933,623 2,710,881 2,928,366 3,031,699 3,392,015 18,118,664
EAST COAST 9,129,635 9,636,697 9,011,323 8,611,199 8,538,073 7,881,670 52,808,597
THAMES 854,483 909,141 1,291,103 838,185 758,257 696,012 5,347,181
SOUTH COAST 5,613,538 5,628,008 5,399,080 5,658,262 5,148,959 5,389,346 32,837,193
S. WEST COAST 1,602,394 1,549,431 1,467,122 1,515,241 1,633,383 1,591,610 9,359,181
N. WEST COAST 316,090 421,068 482,270 470,962 558,398 611,983 2,860,771
RIVERS & MISC 46,120 73,047 78,597 85,153 99,079 124,506 506,502
------------------------ --------------- --------------- ---------------- ---------------- --------------- --------------- -----------------
YEARLY TOTAL 20,684,340 21,151,015 20,440,376 20,107,368 19,767,848 19,687,142 121,838,089
According to moisture content and stone to sand ratio, there's usually between 1.6 and 1.9 metric tonnes weight for
each cubic metre of aggregate. That related to uses a dry weight ratio of 1.72:1. Therefore, the six year total take of
121,838,089 tonnes would mean a removal of 70,836,052 cubic metres.The level given is undoubtedly that landed to
destination. In practice over twice this would have been extracted as some half is rejected by washing off back to the
sea so as to hold the prime coarse cohesive sand and gravel to be used for the best grade concrete.
Such a quantity is difficult to visualise, but can be estimated by theoretically placing it on top of a town or city of a
known area. (Don't try this in practice unless you can chose Westminster) and calculating how high it would reach,
or how many times it would fill the Albert Hall. If any of you feel like showing this graphically or pictorially and letting
me have a copy for our website it would be appreciated as it would help visualise the situation we now have.
It is interesting to note that the findings of erosion of each area correlate quite powerfully with the levels taken, as does
the lowering of the seabed when related to the cumulative active dredging areas.
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