4 Environmental Impacts of Sand Mining

In the last 20 years, the demand for sand mining for building materials has tripled, amounting to 50 billion metric tons annually. However much attention has not been given to the environmental impacts of sand mining. Well, we are here to do justice to that.

Urgent action is needed to avoid a “sand crisis”, says the United Nations Environment Programme.

Five key initiatives are listed in a recent World Economic Forum report to help the cement and concrete industry lessen its environmental effects.

Indeed, cities are constructed on sand. The need for sand-based building materials, glass, and concrete is rising as the world gets more urbanized. Up to 68% of people on the planet are expected to live in cities by 2050.

However, to provide housing for those people, industrial sand mining, also known as aggregate extraction, is occurring more quickly than the replenishment of the materials. This process involves removing sand and gravel from river beds, lakes, the ocean, and beaches for use in construction. This has a negative influence on the ecosystem.

Facts About Sand Mining

Every year, almost six billion tons of sand are dredged from the oceans throughout the globe. Sand dredging may make coastal communities more vulnerable to flooding, according to the UNEP. According to recent UN estimates, almost six billion tons of sand are dredged annually from the world’s ocean floor.

Sand is the most used natural resource worldwide, after water, according to data released by the UN Environment Programme’s (UNEP) Centre for Analytics. Concrete, glass, and technology like solar panels are all made from sand.

Dredging is occurring at a rate that is increasing and getting close to the natural replenishment rate of 10–16 billion tonnes, according to data from Marine Sand Watch.

Six billion of the estimated 50 billion tons of sand and gravel used annually worldwide come from the world’s oceans and seas, according to the association.

Sand dredging may have a major effect on coastal communities and biodiversity. Coastal communities will depend on sand to fortify their coastlines against the threat of increasing sea levels and severe weather events like hurricanes.  

According to the UNEP, adequate sand levels also facilitate the offshore energy sector, which includes the building of wind and wave turbines.

Environmental Impacts of Sand Mining

• Riparian Habitat, Flora and Fauna
• Structural Stability
• Groundwater
• Water Quality

1. Riparian Habitat, Flora and Fauna

Beyond the immediate mine sites, instream mining may have additional expensive repercussions. Every year, riparian areas that support wildlife habitats and abundant supplies of timber are lost, along with many hectares of productive streamside land.

Recreational potential, biodiversity, and fisheries productivity are all negatively impacted by degraded stream ecosystems. Severely damaged channels may diminish land and aesthetic values.

For long-term life, every species needs a certain set of environmental conditions. Native plants in streams have developed special adaptations to the environmental circumstances that prevailed before significant human intervention.

These have led to significant habitat alterations that have benefited some species over others and decreased biological diversity and productivity overall. The stability of the channel bed and banks in the majority of streams and rivers has a direct impact on the quality of the ecosystem.

Most aquatic species cannot survive in unstable stream channels. Variations in the amount of silt available frequently cause bed and bank instability and cause significant channel readjustments.

For instance, riparian forest cutting and instream mining are two examples of human activities that hasten stream bank erosion and turn stream banks into net sources of sediment, which frequently have detrimental effects on aquatic life.

Bed instabilities brought on by anthropogenic activities that artificially lower stream bed elevation create a net release of silt in the surrounding area. Many aquatic animals’ stream habitats are made simpler and worse by unstable sediments. These impacts are beneficial to few animals.

The two main consequences of instream sand mining on aquatic environments are sedimentation and bed deterioration, both of which can seriously harm aquatic life.

The delicate balance between streamflow, sediment supplied from the watershed, and channel design determines the stability of both gravel-bed and sand-bed streams.

Channel and habitat development processes are disrupted by mining-induced changes in sediment supply and channel structure. Additionally, habitats silt downstream as a result of unstable substrate movement. The mining intensity, particle sizes, stream flows, and channel morphology all determine how far something is affected.

Faunal populations decline as a result of habitat loss in the aquatic ecosystem, above and below ground, caused by the total removal of vegetation and degradation of the soil profile.

Fish migration between pools is impeded by channel widening, which shallows the streambed and creates braided or subsurface intergravel flow in riffle zones.

As deep pools fill with gravel and other materials, the channel becomes more uniformly shallow, resulting in a decrease in the diversity of the habitat, the structure of riffle pools, and the population of large predatory fish.

2. Structural Stability

In-stream channels, sand, and gravel mining can cause harm to both public and private property. Gravel mining can generate channel incisions that expose subsurface pipelines and other infrastructure and jeopardize bridge piers.

The two main types of instream mining that induce bed deterioration are:

• Pit excavation
• Bar skimming

Channel incision, another name for bed degradation, is caused by two main processes:

• Headcutting
• “Hungry” water

Headcutting involves excavating a mining hole in the active channel, which lowers the stream bed and produces a nick point that enhances flow energy and locally steepens the channel slope. A nick point experiences bed erosion that progressively spreads upstream during heavy floods.

Significant amounts of streambed silt are mobilized by headcutting and are subsequently carried downstream to deposit in the excavated region and other downstream areas.

Effects downstream of mining sites in gravel-rich streams may not last long after mining is completed because the equilibrium between sediment input and conveyance at a site can quickly recover.

In streams with little gravel, effects might arise quickly and last for many years after mining is completed. Headcutting is still a problem in both gravel-rich and gravel-poor streams, regardless of the effects it has downstream.

Headcuts frequently travel great distances upstream and into tributaries; in certain watersheds, they may even travel as far as the headwaters before being stopped by natural or man-made barriers.

When minerals are extracted, the channel’s flow capacity is increased, which results in a second type of bed degradation. Locally, bar skimming increases flow width and pit excavation increases flow depth.

Sediments from upstream locations deposit at the mining site as a result of both circumstances producing slower streamflow velocities and lower flow energy.

The amount of transported material leaving the site is now smaller than the flow’s capacity to carry sediment as streamflow advances beyond the site and flow energy rises in response to the “normal” channel form downstream.

This “hungry” water, or sediment-deficient flow, pulls up more sediment from the stream that runs beneath the mining site, hastening the process of bed degradation. This state of affairs persists until the site’s input and output of sediments are again in balance.

Below dams, where material is trapped and “hungry” water is released downstream, channel incision typically results. This has a similar effect. This issue is exacerbated by instream mineral extraction occurring downstream of dams.

While levees, bank protection, and modified flow regimes also encourage channel incision, mineral extraction rates in many streams are frequently orders of magnitude higher than the watershed’s supply of sediment, indicating that extraction is primarily to blame for the observed changes in channels.

Hunger-water impacts susceptibility would depend on the extraction rate and the rate of replenishment. Streams with little gravel content would be more vulnerable to disruption.

In addition to creating vertical instability in the channel bed, the channel incision also widens the channel and accelerates stream bank erosion, which results in lateral instability.

When the mechanical qualities of the bank material are unable to support the weight of the material, the incision raises the height of the stream bank and causes bank failure. When deep pools fill with gravel and other sediments, channel widening results in the streambed becoming shallower.

Extreme temperature fluctuations in the stream are further increased by channel enlargement and sinking, and sediment transfer downstream is accelerated by channel instability.

Before significant channel-adjustment flows happen, it may take several years for mining-induced bed degradation and other channel alterations to manifest, and these changes may last long after extraction is completed.

3. Groundwater

In addition to endangering bridges, sand mining turns riverbeds into sizable, deep holes. This causes the groundwater table to fall, which dries out the drinking water wells on the embankments of these rivers.

Bed degradation from instream mining decreases the height of streamflow and the floodplain water table, which in turn can destroy water table-dependent woody plants in riparian areas and decrease wetted periods in riparian wetlands. Saline water may seep into freshwater bodies in areas that are near the sea.

4. Water Quality

The water quality of the river will be impacted by instream sand mining operations.

The effects include higher short-term turbidity at the mining site from sediment resuspension, sedimentation from organic particle matter and excess mining material stockpiling and dumping, and oil spills or leaks from excavation equipment and moving vehicles.

The amount of suspended particles in the water at the excavation site and downstream increases due to increased riverbed and bank erosion. Aquatic ecosystems and water users may be negatively impacted by suspended particles.

If water users downstream of the property are abstracting water for residential use, the impact will be especially great. Costs associated with treating water can be greatly increased by suspended particles.

What can be done to avoid a sand crisis?

Governments are under increasing pressure to regulate sand mining, but more work needs to be done to discover alternatives for use in building and to address the ongoing housing issues that the globe is facing. In Singapore, for instance, recovered glass trash is being utilized instead of sand in 3D-printed concrete.

Ten suggestions are listed in the UNEP report to prevent a sand crisis, which would strike a compromise between environmental preservation and the needs of the construction sector:

How the UNEP says we can prevent a sand disaster. Picture: UNEP

According to UNEP, sand needs to be recognized as a “strategic resource at all levels of government and society,” and ecosystems that have been harmed by sand mining operations need to be repaired for sand resource management to be “just, sustainable, and responsible.”

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