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

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

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

  1. 1. Epitome 1. 2. 3. 4. 5. • Introduction • Impacts of sand mining / gravel extraction • Fundamental considerations in all sand mining operations • Summary • References
  2. 2. 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
  3. 3. 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 The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  4. 4. 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
  5. 5. 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
  6. 6. The detrimental effects to biota resulting from bed material mining are caused by three main processes 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 The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  7. 7. Aggregate mining involves the channel and boundary but requires land access and material storage Instream habitat Potential impacts of sand mining Riparian habitat The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  8. 8. Figure 2.1: Instream habitat (Left) and Riparian habitat (Right) The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  9. 9. 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
  10. 10. Types of instream habitats a) b) c) d) e) f) g) h) i) Log structures Log jams Cover structures Boulders structures Gabion Brush bundle Spawning pads Rubble mats Sediment traps The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  11. 11. 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
  12. 12. • 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 fish become die The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  13. 13. b. Bed degradation, changes morphology of the channel the 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 The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  14. 14. 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. Figure 2.2: Turbid water due to sand mining The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  15. 15. 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
  16. 16. e. Removal or disturbance instream roughness elements of 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
  17. 17. 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
  18. 18. 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
  19. 19. 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
  20. 20. b. Lowered floodplain groundwater o Riparian vegetation reliant on the groundwater will subsequently be stressed c. Permanent flooding o Subsequently causes annual flooding into the disturbed site. The Impact on River Sand Mining on Environment or frequent W.A.Dulanjali M. Wijethilake
  21. 21. 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
  22. 22. 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
  23. 23. 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
  24. 24. 1 4 2 5 3 6 The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  25. 25.  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
  26. 26. Physical The Impact on River Sand Mining on Environment Water quality Ecological W.A.Dulanjali M. Wijethilake
  27. 27. The potential impacts of sand mining are : Bed degradation and consequent effects on channel and bank stability Figure 2.3: Slumped/Exposed Bank due to Unrestricted Mining Activities The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  28. 28. 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
  29. 29. 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
  30. 30. Figure 2.4 : Extensive Modification to Stream Channel Caused by sand mining The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  31. 31. 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
  32. 32. Figure 2.5 : Yellow boy in a streams The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  33. 33. There are several factors consider when sand mining in particular area 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
  34. 34. 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. The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  35. 35. Epitome 1. 2. 3. 4. 5. 6. • Introduction • Impacts of sand mining / gravel extraction • Fundamental considerations in all sand mining operations • Status of Sri Lanka • Summary • References
  36. 36. 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
  37. 37. 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
  38. 38. The Impact on River Sand Mining on Environment W.A.Dulanjali M. Wijethilake
  39. 39. 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 http://threeissues.sdsu.edu/three_issues_sandminingfacts01.html from Rathnayake, R., (2012). Unregulated / Illicit River Sand Mining in Sri LankaImpact 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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