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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
THANK YOU