Marine Sand
Shareef of GSI Marine Wing Mangalore has these suggestions in his Current Science article
| Offshore sand: An alternative? | |
| N. M. Shareef |
Sand is an essential material for construction purpose, and there is no alternative to it till date. The demand for constructiongrade sand in our country is increasing day by day due to the boom in construction fuelled by economic prosperity. Such a huge demand is pushing people to dig into the deeper bosoms of the traditional sources of sand, like riverbeds, lagoons, beach dunes, etc. exerting severe stress on these sources. Unmindful and indiscriminate sand mining not only depletes these natural resources, but also creates environmental problems. The environmental impact of unscientific and unscrupulous exploitation of these precious natural resources is well documented in the scientific literature. The impact of such exploitation is of late being felt by the people who are living inthe vicinity of the mining areas. The administration and civil society seem to be callous in their approach to such issues and remain contented by satiating their wants without thinking about the planet earth, which they owe to the next generation.
Consequences of riverbed sand mining include depletion of groundwater, saline intrusion, destruction of agricultural land, loss of employment to farm workers, threats to livelihood, destruction of ecosystems and even human rights violation. Uncontrolled sand mining from the riverbed leads to the destruction of the entire river system. Sand acts like a sponge, which helps in recharging the water table. Once this layer is removed, the hydrodynamics of the river gets disturbed and affects the velocity of water flow. This also enhances the penetration of sunlight deep into the soil, which aggravates the groundwater evaporation. Excessive instream sand and gravel mining lower the river bottom, which distorts the flow regime leading to the river bank erosion. As the trucks race to the middle of the river to collect sand, a bit of the riverbed dies every day. Such destruction destroys the entire habitat in the area. Depletion of the sand in the stream bed and along the coastal areas causes deepening of rivers and estuaries and enlargement of river mouth and coastal inlets. The direct consequences of this is the easy intrusion of saline, water especially during high tides. Once the saline water intrudes into the stream, it destroys the ecosystem. Widening of the river mouths and tidal inlets may expose the entire area to become vulnerable to storm surges and cyclones.
The booming construction industry however requires sand, as there is no alternative to substitute it. The time has come to explore an alternate to this traditional source, and offshore sand gives a ray of hope. Whenever there is a mention about offshore sand, people have a misconception that its refers to the beach and near beach sand. No doubt, these areas are ecologically highly sensitive and any disturbance to it will have serious implications on the beach and its processes.
Sand occurring beyond 25 m water depth and beyond the territorial waters seems to be the answer to the imperatives. The Marine Wing of the Geological Survey of India has already established the reserves of several million tonnes of construction-grade sand in the offshore of Kerala coast (Marine Wing Newsl., Geological Survey of India, vol. xx, No. 1 & 2, March–September 2006). Such a huge resource, if exploited commercially without destroying the environment, will be a viable substitute for the over-exploited traditional sources of sand. Offshore sand mining will have minimum effect on the physical environment of the sea as it does not affect the wave dynamics and beach profile. Mining them will have minimum impact on the beach process because there is no cross transportation either from the beach to these deposits or vice versa. Also the said resource is beyond 30 km from the shoreline. These sand bodies are remnants of submerged strand line deposits left behind when thesea moved landward during the last transgression. Similarly, the shelf break in the west coast is wider compared to that in the east coast and the gradient of the shelf is roughly 1 m ´ 500–1000 m. This offshore sand as we understand, is naked sand without any overburden and its extraction will not require any removal of the overburden which may again agitate the sea bottom. The main attraction of these sand bodies is that they comprise all the grades of sand, both for construction as well as for the glass industry.
Although the impact of offshore sand mining on the physical environment of the sea will be minimal, its impact on the biological environment has to be studied in detail before taking any decision. Since sand mining at these depths has not been carried out before, provision must be made to enable scientific monitoring and gathering of information. Specific impact assessment should be done for each area. Understanding the impact of any aggression on the planet earth is essential for sustainable development.
N. M. SHAREEF
Geological Survey of India,
Marine Wing,
Mangalore 575 001, India
e-mail: Shareef_n123@rediffmail.com
Consequences of riverbed sand mining include depletion of groundwater, saline intrusion, destruction of agricultural land, loss of employment to farm workers, threats to livelihood, destruction of ecosystems and even human rights violation. Uncontrolled sand mining from the riverbed leads to the destruction of the entire river system. Sand acts like a sponge, which helps in recharging the water table. Once this layer is removed, the hydrodynamics of the river gets disturbed and affects the velocity of water flow. This also enhances the penetration of sunlight deep into the soil, which aggravates the groundwater evaporation. Excessive instream sand and gravel mining lower the river bottom, which distorts the flow regime leading to the river bank erosion. As the trucks race to the middle of the river to collect sand, a bit of the riverbed dies every day. Such destruction destroys the entire habitat in the area. Depletion of the sand in the stream bed and along the coastal areas causes deepening of rivers and estuaries and enlargement of river mouth and coastal inlets. The direct consequences of this is the easy intrusion of saline, water especially during high tides. Once the saline water intrudes into the stream, it destroys the ecosystem. Widening of the river mouths and tidal inlets may expose the entire area to become vulnerable to storm surges and cyclones.
The booming construction industry however requires sand, as there is no alternative to substitute it. The time has come to explore an alternate to this traditional source, and offshore sand gives a ray of hope. Whenever there is a mention about offshore sand, people have a misconception that its refers to the beach and near beach sand. No doubt, these areas are ecologically highly sensitive and any disturbance to it will have serious implications on the beach and its processes.
Sand occurring beyond 25 m water depth and beyond the territorial waters seems to be the answer to the imperatives. The Marine Wing of the Geological Survey of India has already established the reserves of several million tonnes of construction-grade sand in the offshore of Kerala coast (Marine Wing Newsl., Geological Survey of India, vol. xx, No. 1 & 2, March–September 2006). Such a huge resource, if exploited commercially without destroying the environment, will be a viable substitute for the over-exploited traditional sources of sand. Offshore sand mining will have minimum effect on the physical environment of the sea as it does not affect the wave dynamics and beach profile. Mining them will have minimum impact on the beach process because there is no cross transportation either from the beach to these deposits or vice versa. Also the said resource is beyond 30 km from the shoreline. These sand bodies are remnants of submerged strand line deposits left behind when thesea moved landward during the last transgression. Similarly, the shelf break in the west coast is wider compared to that in the east coast and the gradient of the shelf is roughly 1 m ´ 500–1000 m. This offshore sand as we understand, is naked sand without any overburden and its extraction will not require any removal of the overburden which may again agitate the sea bottom. The main attraction of these sand bodies is that they comprise all the grades of sand, both for construction as well as for the glass industry.
Although the impact of offshore sand mining on the physical environment of the sea will be minimal, its impact on the biological environment has to be studied in detail before taking any decision. Since sand mining at these depths has not been carried out before, provision must be made to enable scientific monitoring and gathering of information. Specific impact assessment should be done for each area. Understanding the impact of any aggression on the planet earth is essential for sustainable development.
N. M. SHAREEF
Geological Survey of India,
Marine Wing,
Mangalore 575 001, India
e-mail: Shareef_n123@rediffmail.com
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