IMPACT OF SAND AND GRAVEL DREDGING ON THE ENVIRONMENT

jane doe

4 weeks ago

IMPACT OF SAND AND GRAVEL DREDGING ON THE ENVIRONMENT

ABSTRACT

For thousands of years, sand and gravel have been used to build roads and structures. Today, the demand for sand and gravel is increasing. Mining operators, in collaboration with relevant resource agencies, must work to ensure that sand mining is done responsibly.

Excessive in-stream sand and gravel mining degrades rivers. In-stream mining lowers the stream bottom, potentially leading to bank erosion. Sand depletion in the streambed and along coastal areas causes rivers and estuaries to deepen, as well as the expansion of river mouths and coastal inlets. It may also cause saline-water intrusion from the nearby sea. The impact of mining is exacerbated by the effects of sea level rise. Any amount of sand exported from streambeds and coastal areas is a loss for the system.

Chapter one

1.1 Background of the Study

Excessive instream sand and gravel mining degrades rivers. Instream mining lowers the stream bottom, potentially leading to bank erosion. Sand depletion in the streambed and along coastal areas causes rivers and estuaries to deepen, as well as the expansion of river mouths and coastal inlets. It may also cause saline-water intrusion from the nearby sea. The impact of mining is exacerbated by the effects of sea level rise. Any amount of sand exported from streambeds and coastal areas is a loss for the system.

Excessive instream sand mining is a threat to bridges, river banks and other infrastructure. Sand mining also impacts the nearby groundwater system and the uses that local people make of the river.

Instream sand mining results in the degradation of aquatic and riparian ecosystems through substantial changes in the channel morphology. Impacts include bed degradation, bed coarsening, decreasing water tables near the streambed, and channel instability. These physical consequences induce degradation of riparian and aquatic biota and may lead to the crumbling of bridges and other infrastructure. Continued extraction may potentially cause the entire streambed to erode to the depth of excavation.

Sand mining causes more vehicle traffic, which negatively degrades 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). They were formed by erosive processes over thousands of years and are now being extracted at a much faster rate than they are being renewed.

Despite our growing reliance on massive amounts of sand and gravel, as well as the enormous negative environmental impact of their extraction, policymakers have mostly neglected this issue, and the general public is largely unaware of it. Indeed, the lack of global data on aggregates mining complicates environmental assessment and contributes to a lack of awareness about the problem. As a result, there is a significant disparity between the size of the problem and public knowledge of it.

1.2 Statement of the Problem

The impact of sand and gravel dredging or mining on the ecosystem is considerable, since when people see it dredge Excessive stream sand and gravel mining degrades waterways. Any amount of sand exported from streambeds and coastal areas is a loss for the system. Excessive in stream sand mining is a threat to bridges, river banks and other infrastructure.

With growth in technology and infrastructural development, the requirement for sand and gravel is on the high side, and dredging occurs to be the sole method to meet this needs. However if dredging and is not control it influence on the infrastructure might be very catastrophic.

1.3 OBJECTIVE OF THE STUDY

The major purpose of this study was to assess the influence of sand and gravel dredging on environment. However at the completion of the study, the researcher seeks to achieve the following objectives:

The impact of gravel dredging on the Lagos bar beach coastal area
The influence of sand dredging on Nigerian seas
To ascertain the consequences of gravel dredging in coastal area
The challenges of dredging on Nigeria coastal area
1.4 RESEARCH QUESTION

To ensure the successful completion of these studies, the following research question was developed:

What is the impact of dredging on the Lagos coastline?
What is the impact of sand dredging in Nigerian waterways, with a focus on the Lagos coastline?
What impact does gravel dredging have on infrastructure development in the Lagos coastal area?
How has dredging affected the region’s infrastructure development?
1.5 Significance of the Study

It is expected that once the studies are completed, the findings will be beneficial to the environmental agency and coastal guard who are in charge of protecting the region. The study will also benefit NIMASA, which is in charge of protecting Nigerian waterways.

Finally, the study will also benefit academia, instructors, lecturers, researchers, and the general public.

1.6 SCOPE AND LIMITATION OF THE STUDIES

The scope of this study covers the impact of sand and gravel dredging on the Lagos coastal area, but the studies have some constraints, which are:

a) AVAILABILITY OF RESEARCH MATERIAL: The researcher has insufficient research material, which limits the investigation.
b) TIME: The study’s time frame does not allow for wider coverage because the researcher must combine other academic activities and examinations with the study.
c) FINANCE: The funding available for the research does not allow for broader coverage because the researcher’s resources are limited due to other academic obligations.
1.7 Definition of Terms

DREDGING

Dredging is an excavation activity that is typically carried out underwater, in shallow seas or freshwater areas, with the goal of collecting 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 substance made up of finely split rock and mineral particles. It is distinguished by size, being finer than gravel but coarser than silt. Sand can also refer to a soil’s textural class or kind, such as a soil that contains more than 85% sand particles by mass.

Sand composition varies depending on local rock sources and conditions, but the most frequent ingredient of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the form of quartz. Calcium carbonate, such as aragonite, is the second most frequent type of sand and was mostly formed during the last half billion years by various forms of life, such as coral and shellfish. For example, it is the predominant type of sand found in regions where reefs have dominated the ecology for millions of years, such as 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 streets are surfaced with gravel, especially in rural areas where there is little traffic. Globally, much more roads are paved with gravel than with concrete or tarmac; Russia alone has over 400,000 km (250,000 mi) of gravel roads.[1] Sand and tiny gravel are also crucial for the production of concrete.

1.8 Organisation of the Study

This research study is organised into five chapters for simple understanding, as follows:

The first chapter is concerned with the introduction, which includes the (overview of the study), statement of problem, aims of the investigation, research question, significance of the study, research methods, term definitions, and historical backdrop of the study. The second chapter is on the theoretical framework that underpins the study, as well as a review of relevant literature. Chapter three discusses the research design and technique used in the study. Chapter four focusses on data gathering, analysis, and presenting of findings. Chapter five presents the study’s summary, conclusion, and recommendations.