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Impact Of Sand And Gravel Dredging On The Environment
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1.7 DEFINITION OF TERMS
DREDGING
Dredging
is an excavation activity usually carried out underwater, in shallow
seas or freshwater areas with the purpose of gathering up bottom
sediments and disposing of them at a different location. This technique
is often used to keep waterways navigable. It is also used as a way to
replenish sand on some public beaches, where sand has been lost because
of coastal erosion. Fishing dredges are used as a technique for catching
certain species of edible clams and crabs.
SAND
Sand is a
naturally occurring granular material composed of finely divided rock
and mineral particles. It is defined by size, being finer than gravel
and coarser than silt. Sand can also refer to a textural class of soil
or soil type; i.e. a soil containing more than 85% sand-sized particles
by mass.
The composition of sand varies, depending on the local rock
sources and conditions, but the most common constituent of sand in
inland continental settings and non-tropical coastal settings is silica
(silicon dioxide, or SiO2), usually in the form of quartz. The second
most common type of sand is calcium carbonate, for example aragonite,
which has mostly been created, over the past half billion years, by
various forms of life, like coral and shellfish. For example, it is the
primary form of sand apparent in areas where reefs have dominated the
ecosystem for millions of years like the Caribbean.
GRAVEL
Gravel
is composed of unconsolidated rock fragments that have a general
particle size range and include size classes from granule– to
boulder-sized fragments. Gravel is categorized by the Udden-Wentworth
scale into granular gravel (2 to 4 mm or 0.079 to 0.157 in) and pebble
gravel (4 to 64 mm or 0.2 to 2.5 in). One cubic metre of gravel
typically weighs about 1,800 kg (or a cubic yard weighs about 3,000
pounds).
Gravel is an important commercial product, with a number of
applications. Many roadways are surfaced with gravel, especially in
rural areas where there is little traffic. Globally, far more roads are
surfaced with gravel than with concrete or tarmac; Russia alone has over
400,000 km (250,000 mi) of gravel roads.[1] Both sand and small gravel
are also important for the manufacture of concrete
1.8 ORGANIZATION OF THE STUDY
This research work is organized in five chapters, for easy understanding, as follows
Chapter
one is concern with the introduction, which consist of the (overview,
of the study), statement of problem, objectives of the study, research
question, significance or the study, research methodology, definition of
terms and historical background of the study. Chapter two highlight the
theoretical framework on which the study its based, thus the review of
related literature. Chapter three deals on the research design and
methodology adopted in the study. Chapter four concentrate on the data
collection and analysis and presentation of finding. Chapter five gives
summary, conclusion, and recommendations made of the study.
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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---
