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Geohazards

Engineering Geology. Geohazards. Planning with nature. Water management. Surface water, groundwater Quantity, quality Environmental allocations, water re-use land-use vs. water use. Carbon management. CO 2 reduction, sequestration Carbon tax, carbon market Biofuels, plantations

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Geohazards

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  1. Engineering Geology Geohazards Planning with nature

  2. Water management • Surface water, groundwater • Quantity, quality • Environmental allocations, water re-use • land-use vs. water use Carbon management • CO2 reduction, sequestration • Carbon tax, carbon market • Biofuels, plantations • Sustaining biodiversity Geohazard management • Soil erosion & landslides • Salinity, waterlogging • Floods, sediment movement • Coastal erosion & deposition Socio-geographic management • Urbanisation, peri-urban growth • Coastal development • Changing agricultural communities • Threats to biodiversity NRM issues (current, emerging, urgent)

  3. Geohazards Earthquakes Tsunamis Floods Coastal erosion Volcanic eruptions Permafrost Soil erosion Landslides and rockfalls Sinkholes and collapsing soils Acid sulfate soils Reactive soils Salinity and sodicity Karst and soluble rocks Contaminated soils

  4. Geohazards – Volcanic hazards Hawaii

  5. Geohazards – Volcanic hazards Pyroclastic flows Lahars Gas emissions Dust Climate changes Environmental devastation Washington

  6. Geohazards - Earthquakes Measured by magnitude & intensity Earthquake wave components – P, S, L, R • Greatest loss of life for geohazards e.g. • Aleppo, Syria 1138, 230,000 dead • Shaanxi, China 1556, 830,000 dead • Lisbon, Portugal 1755, 100,000 dead • Gansu, China 1920, 200,000 dead • Tokyo, Japan 1923, 140,000 dead • Tangshan, China 1976, 242,000 dead • Sumatra, Indonesia 2004, 230,000 dead Knock-on effects = Tsunamis, landslides, fires, diseases, famine, etc.

  7. Japan 11th March 2011 ML 9.0 20,448 dead

  8. Canterbury, N.Z. 2010 & 2011

  9. Geohazards - Earthquakes • Likelihood • Historic data collection and collation • Seismic record • Geology mapping • Fault mapping • Soil mapping • Microsiesmic surveys • Consequence • Historic data collection and collation • Building susceptibility (homes, hospitals, public offices…) • Infrastructure susceptibility (road, bridges, sewerage…) • Utility conduits (gas, power, water, telecommunications…) • Industry (refineries, biohazards, nuclear hazards…) • Emergency services (police, ambulance, fire…)

  10. Geohazards - Landslides Wild Dog Road, 1979

  11. Geohazards - Landslides Landslide mechanics

  12. Geohazards - Landslides Landslide mechanics Gravity Water Loads Destabilising forces Undercutting

  13. Landslide mechanics Retain the slope Anchor the slope Stabilising forces Unload the slope Drain the slope

  14. Geohazards - Landslides Wild Dog Road, 1952 Wild Dog Road, 1979 Barham Valley, 1986 Wongarra, 2000

  15. Geohazards - Landslides Lake Elizabeth Landslide 48 Ha of mature forest slid into the East Branch of the Barwon River in Late June 1952, following heavy rain. Forming a dam 400 metres wide and 30 metres high. The top 26 metres of the dam was breached in August 1953 sending a 7 metre wall of mud downstream. Lake Elizabeth filled

  16. Geohazards - Landslides Rock slide begins Cable anchors installed By 1971, 3000 tonnes of rock are Sliding at 2cm per day. A further 150000 tonnes threaten Movement. Material removed to widen the Great Ocean Road, 1968 Windy Point Rockslide Great Ocean Road opened December 1971 Great Ocean Road closed July 1971

  17. Geohazards - Landslides Wongarra Moonlight Head Birregurra Elliminyt

  18. Riverside Dr Boulevarde Dunoon Av Morley Av Wye River

  19. Moorabool River 2001 Element at risk = urban water supply for Bannockburn & Geelong. Remediation costs ~ $500,000

  20. Grampians National Park 2011

  21. Grampians 2011

  22. Geohazards - Rockfalls Barwon Heads October 2000

  23. Geohazards – Soil erosion by water & wind Elaine

  24. Tunnel erosion – Separation Creek Sheet erosion - Morrisons Wind erosion - Chinkapook Gully erosion - Moreep

  25. Geohazards – Soil erosion by water Sheet erosion Rill erosion Channels < 0.3m depth Universal Soil Loss Equation Annual soil loss (t/ha/yr) = Rainfall erosivity x soil erodibility x slope length x slope gradient x support practice factor x cover and crop management Gully erosion Channels > 0.3m depth Sediment transport Water flow Headward erosion Tunnel erosion Soil aggregate stability (slaking and dispersion) Erosion mechanics

  26. Regional cost Infrastructure: roads, pipelines, buildings, cables, reservoirs Agricultural: dairy pasture, farm dams, farm infrastructure, horticultural land, grazing land, cropping land Environmental: environmental stream flows, lakes and wetlands, native forests, coastal cliffs, public access to tourist sites, and river gorges. Water quality: turbidity, sediment load Cultural and Heritage: public access (particularly coastal), historic buildings Estimated at ~ $2 million/yr since 1950

  27. Erosion impacts on waterways and wetlands Illabarook

  28. near Geelong

  29. St Paul, South Africa - donga

  30. Ground subsidence • Sinkholes, collapsing ground caused by: • Groundwater extraction from confined aquifers (see week 7) • Dissolution of aquifer materials (e.g. karst processes) • Dispersive or slaking soils • Man made cavities (e.g. Mines)

  31. Dissolution of the aquifer Example: Lake Peigneur, Louisiana 1980 drilling causes a lake to drain into a salt mine (Google it and watch the video) Karst processes Limestone cavities result from dissolution of the aquifer by groundwater. The cavities grow larger over time and then collapse to form dolines.

  32. Tropical storm “Agatha” (May 29th – 30th 2010) Death toll 179 and rising Landslides in El Salvador, Sinkhole in Guatemala 20m diameter, 30m deep Sinkhole in Guatemala City Sunday May 30th 2010 Similar event February 2007

  33. Geohazards - Subsidence • Subsidence over old mine workings (Ballarat, Bendigo, Wonthaggi) abandoned quarries (Yarraville), • Karst solution cavities (Port Campbell, Peterborough), • Dispersive soils (Kennet River, Melton, Parwan Valley)

  34. Mexico City Subsidence due to groundwater extraction threatens historic buildings such as the cathedral (1573 – 1813). About 1m recent subsidence Plumb-bob to check restoration success

  35. Mexico City Old Basilica of Guadalupe (1531 – 1709) Up to 8.5m of subsidence has been recorded in Mexico City Earth fractures on the outskirts of Mexico City show the extents of the subsidence (tensile cracks around the rim of the subsidence crater)

  36. Geohazards – Acid sulfate soils • Acid sulfate soils (ASS) • Coastal ASS (CASS) • Inland ASS (IASS) • Potential ASS (PASS) • Actual ASS (AASS) • Contain iron sulfides (e.g. pyrite) • Produce sulfuric acid when disturbed • Irreversible process • Severe damage to built and natural environment • Often contaminate soils with other toxins • AASS has pH <4 Breamlea

  37. Geohazards – Acid sulfate soils Tyrell Crk

  38. Geohazards – Reactive soils • Soils which swell when wetted and shrink when dried. • Victoria’s most prevalent geohazard • Costs $millions per year in damage to houses, roads, utility services, etc. • Whole industry dedicated to soil tests for building. • Australian Standard AS2870 • Soils which contain certain clay minerals usually montmorillonite, but may be others. • Easily identified by soil classification tests. • Managed by building codes and specialist engineering solutions. • Can be stabilised by the use of soil additives.

  39. Summary Landscapes are dynamic. Geohazards are natural processes Geohazards can also be man-made (anthropogenic) Identify the processes that occur in different landscapes, and the main factors (natural or man-made) that are acting on those processes Assess the risk to assets (life, property, environment, social, etc.) Where risk is unacceptable, reduce the risk by changing the likelihood of an event or its consequence Port Campbell

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