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.