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Impact Of Sand And Gravel Dredging On The Environment
CHAPTER ONE -- [Total Page(s) 3]
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CHAPTER ONE
1.1 BACKGROUND OF THE STUDY
For thousands of years,
sand and gravel have been used in the construction of roads and
buildings. Today, demand for sand and gravel continues to increase.
Mining operators, in conjunction with cognizant resource agencies, must
work to ensure that sand mining is conducted in a responsible manner.
Excessive
instream sand-and-gravel mining causes the degradation of rivers.
Instream mining lowers the stream bottom, which may lead to bank
erosion. Depletion of sand in the streambed and along coastal areas
causes the deepening of rivers and estuaries, and the enlargement of
river mouths and coastal inlets. It may also lead to saline-water
intrusion from the nearby sea. The effect of mining is compounded by the
effect of sea level rise. Any volume of sand exported from streambeds
and coastal areas is a loss to the system.
Excessive instream sand
mining is a threat to bridges, river banks and nearby structures. Sand
mining also affects the adjoining groundwater system and the uses that
local people make of the river.
Instream sand mining results in the
destruction of aquatic and riparian habitat through large changes in the
channel morphology. Impacts include bed degradation, bed coarsening,
lowered water tables near the streambed, and channel instability. These
physical impacts cause degradation of riparian and aquatic biota and may
lead to the undermining of bridges and other structures. Continued
extraction may also cause the entire streambed to degrade to the depth
of excavation.
Sand mining generates extra vehicle traffic, which
negatively impairs the environment. Where access roads cross riparian
areas, the local environment may be impacted.
Sand and gravel are
used extensively in construction. In the preparation of concrete, for
each tonne of cement, the building industry needs about six to seven
times more tonnes of sand and gravel (USGS, 2013b). Thus, the world’s
use of aggregates for concrete can be estimated at 25.9 billion to 29.6
billion tonnes a year for 2012 alone. This production represents enough
concrete to build a wall 27 metres high by 27 metres wide around the
equator. Aggregates also contribute to 90% of asphalt pavements and 80%
of concrete roads and the demand for aggregates stems from a wide range
of other sectors, including production of glass, electronics and
aeronautics. Added to this are all the aggregates used in land
reclamation, shoreline developments and road embankments (for which the
global statistics are unavailable), plus the 180 million tonnes of sand
used in industry. This sand and gravel are mined world-wide and account
for the largest volume of solid material extracted globally and the
highest volume of raw material used on earth after water (about 70-80%
of the 50 billion tons material mined/year). Formed by erosive processes
over thousands of years, they are now being extracted at a rate far
greater than their renewal.
Despite our increasing dependence on the
colossal quantities of sand and gravel being used and the significant
negative impact that their extraction has on the environment, this issue
has been mostly ignored by policy makers and remains largely unknown by
the general public. Indeed, the absence of global data on aggregates
mining makes environmental assessment very difficult and has contributed
to the lack of awareness about this issue. As a consequence, a large
discrepancy exists between the magnitude of the problem and public
awareness of it.
1.2 STATEMENT OF THE PROBLEM
The impact of sand
and gravel dredging or mining on the environment is enormous; this is so
because when they see is dredge Excessive in stream sand-and-gravel
mining causes the degradation of rivers. … Any volume of sand exported
from streambeds and coastal areas is a loss to the system. Excessive in
stream sand mining is a threat to bridges, river banks and nearby
structures.
With advancement in technology and infrastructural
development, the need for sand and gravel is on the high side, and
dredging happens to be the only solution to meet this needs. However if
dredging and is not control it impact on the infrastructure can be very
fatal.
CHAPTER ONE -- [Total Page(s) 3]
Page 1 of 3
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ABSRACT - [ Total Page(s): 1 ]For thousands of years, sand and gravel have been used in the construction of roads and buildings. Today, demand for sand and gravel continues to increase. Mining operators, in conjunction with cognizant resource agencies, must work to ensure that sand mining is conducted in a responsible manner.Excessive in-stream sand-and-gravel mining causes the degradation of rivers. In-stream mining lowers the stream bottom, which may lead to bank erosion. Depletion of sand in the streambed and along coasta ... Continue reading---
