Impact of river sand mining on environment by Dulanjali M. Wijethilake

Impact of River Sand Mining on environment

Impact of River Sand Mining on environment

W.A. Dulanjali M. Wijethilake

Aquatic science (Sp.) – Part II

1. • Introduction

2.• Impacts of sand mining /

gravel extraction

3.• Fundamental considerations

in all sand mining operations

4. • Summary

5. • References

Epitome

Introduction Large scale mining of sand and gravel

Increasing demand in the construction sector

Short term benefits

Instream sand mining may not be visible

Sand mining disturbs the equilibrium of a river channel

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

For thousands of years, sand and gravel have been used in the construction of roads and buildings

Excessive instream sand mining is a threat to bridges, river banks and nearby structures

Continued extraction

Sand is an important mineral for our society in protecting the environment

Pollution of the water is evident by the coloration of water which in most of the rivers and streams in the mining area

Contamination of Acid Mine Drainage (AMD)

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Impacts of sand mining / gravel extraction

Direct impact on the stream’s physical habitat characteristics

Channel geometry Bed elevation Substrate composition and stability Instream roughness elements Depth Velocity Turbidity Sediment transport Stream discharge Temperature

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

The detrimental effects to biota resulting from bed material mining are caused by three main processes

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

1. Alteration of the flow patterns resulting from modification of the river bed

2. An excess of suspended sediment

3. Damage to riparian vegetation and instream habitat

Aggregate mining involves the channel and boundary but requires land access and material storage

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Potential impacts of sand mining

Instream habitat

Riparian habitat

Figure 2.1: Instream habitat (Left) and Riparian habitat (Right)

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

01. Instream sand mining & Impacts

Kinds of instream sand mining

Dry-pit Wet pit mining Bar skimming or "scalping." Pits on the adjacent floodplain or river terraces

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Types of instream habitats

a) Log structures

b) Log jams

c) Cover structures

d) Boulders structures

e) Gabion

f) Brush bundle

g) Spawning pads

h) Rubble mats

i) Sediment traps

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Impacts

a. Extraction of bed material in excess of natural replenishment by upstream transport

o This causes bed degradation, increases suspended sediment, sediment transport, water turbidity and sand/gravel siltation

o Becomes unsuitable for many aquatic organisms

o Gravel removal not only impacts for the extraction site

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

• Suspended sediment load

• Reduction in light penetration

• Loss of photosynthesis in micro and macrophytes

• Resulting in reduced food availability and plant biomass

• Reduced visibility of pelagic food, reduced availability of benthic food due to smothering

• Clogging of gill rakers and gill filaments

• Ultimeately

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

fish become die

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

b. Bed degradation, changes the morphology of the channel

o Potential for diversion of flow through

o Migration blockages for fish during low flows

o If the gravel extraction activity is conducted away from the active river channel during low water periods

o As active channels naturally meander, the channel may migrate into

c. Operation of heavy equipment in the channel bed

o Can directly destroy spawning habitat for fish and macroinvertebrate habitat, and produce increased turbidity and suspended sediment downstream.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Figure 2.2: Turbid water due to sand mining

d. Altering channel hydraulics

o Stockpiles and overburden in the floodplain can alter channel hydraulics during high flows.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

e. Removal or disturbance of instream roughness elements

o It negatively affects both quality and quantity of instream habitat.

o Instream roughness elements - particularly large woody debris, play a major role in providing structural integrity to the stream ecosystem.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Many hectares of fertile streamside land are lost annually

Degraded stream habitats result in lost of fisheries productivity, biodiversity, and recreational potential.

Severely degraded channels may reduce land and aesthetic values.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

02. Riparian zone sand mining & Impacts

All species require specific habitat conditions to ensure long-term survival

Unstable stream channels are inhospitable to most aquatic species

The complete removal of vegetation and destruction of the soil profile destroys

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Impacts a. Destruction of the riparian zone

It serves as buffer to pollutants entering a stream from runoff, controls erosion, and provides habitat and nutrient input into the stream.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

b. Lowered floodplain groundwater

o Riparian vegetation reliant on the groundwater will subsequently be stressed

c. Permanent flooding

o Subsequently causes annual or frequent flooding into the disturbed site.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

d. Destruction of riparian vegetation

o This is caused by heavy equipment, processing plants at or near the extraction site

e. Disturbing the natural hydraulics of the riparian zone 

o Generation of recruitment may be lost

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

f. Removal of large woody debris from the riparian zone

o It negatively affects the plant community.

g. Reduced vegetative bank cover

o Resulting in reduced shading and increased water temperatures.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Further impacts ……..

Sand budget

Determining the sand budget for a particular stream reach requires site-specific topographic, hydrologic, and hydraulic information.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Littoral cell

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

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Impacts for groundwater

Bed degradation from instream mining lowers the elevation of stream flow

Saline water may intrude into the fresh water body

Impacts for Water Quality

Increased riverbed and bank erosion

Increased short-term turbidity

Suspended solids can increase water treatment costs

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Impacts of sand mining can be broadly classified into three categories:

Physical Water quality Ecological

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

The potential impacts of sand mining are :

Bed degradation and consequent effects on channel and bank stability

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Figure 2.3: Slumped/Exposed Bank due to Unrestricted Mining Activities

Increased sediment loads, decreased water clarity

Changes in channel morphology and disturbance of ecologically important roughness elements in the river bed

Ecological effects on bird nesting, fish migration etc.

Modification of the riparian zone including bank erosion

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Direct destruction from heavy equipment operation

Discharges from equipment and refueling

Impacts on structures and access

Biosecurity and pest risks

Impacts on coastal processes

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Figure 2.4 : Extensive Modification to Stream Channel Caused by sand mining

Special attention …

Acid Mine Drainage- Threat to water resources 

Acid mine drainage also dissolves toxic metals such as copper, aluminum, cadmium, arsenic, lead and mercury from the surrounding rock

Yellow boy

The impacts to aquatic life may range from immediate fish kills to sub lethal, impact affecting growth, behavior or ability to reproduce

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Figure 2.5 : Yellow boy in a streams

Fundamental considerations in all sand mining operations

There are several factors consider when sand mining in particular area

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

1. Sand mining sites should be situated outside the active floodplain and excavation should not take place from below the water table.

2. Larger rivers and streams should be used preferentially than small rivers and streams.

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

3. bar skimming should not be allowed.

4. Pit excavations located on adjacent floodplain or terraces should be separated from the active channel.

5. The removal or disturbance of instream roughness elements during gravel extraction activities should be avoided.

6. Turbidity levels should be monitored

7. Sand extraction in vegetated riparian areas should be avoided.

8. Operation and storage of heavy equipment within riparian habitat should be restricted.

1. • Introduction

2.• Impacts of sand mining /

gravel extraction

3.• Fundamental considerations

in all sand mining operations

4. • Status of Sri Lanka

5. • Summary

6. • References

Epitome

Summary

The geomorphic effects of river sand mining have involved extraction rates lasting over a decade or more

Instream sand mining results in the destruction of aquatic and riparian habitat through large changes in the channel morphology

Physical impacts cause degradation of riparian and aquatic biota

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

Basically sand mining carrying in two locations. Those are instream sand mining and riparian zone sand mining

In addition sand mining alter the sand budget, ground water and water quality. Special attention goes to Acid Mine Drainage (AMD)

There are 103 river basins in Sri Lanka

The situation is more severe in certain major rivers including Kalu Ganga, Walawe ganga, Kelani ganga , Nilwala ganga , Deduru Oya, Ma Oya and Kirindi Oya

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

According to discussed information, we could clearly realized

river sand mining cause detrimental impacts on environment.

References Concise report of the study done by Volunteer team of Net water. Impact of river sand mining in Ratnapura district in Sabaragamuwa province

Hill, L., Kleynhans, C.J., (1999). Preliminary Guidance document for Authorization and Licensing of Sand Mining / Gravel Extraction, in terms of Impacts on Instream and Riparian Habitats

Impacts of sand mining from http://threeissues.sdsu.edu/three_issues_sandminingfacts01.html

Rathnayake, R., (2012). Unregulated / Illicit River Sand Mining in Sri Lanka- Impact of Awareness Campaign and Legal Recourse

River sand mining management guideline , Ministry of natural resources and environment. Department of irrigation and management in Malaysia. pp 15-20

Saviour, N.M., (2012). Environmental impact of soil and sand mining : A review, International Journal of Science, Environment and Technology, Vol. 1, No 3. pp 126 – 127, 132

The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake

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