Engineering Geology

NRM issues (current, emerging, urgent)

Carbon management• CO2 reduction, sequestration• Carbon tax, carbon market • Biofuels, plantations• Sustaining biodiversity

Socio-geographic management• Urbanisation, peri-urban growth• Coastal development• Changing agricultural communities• Threats to biodiversity

Geohazard management• Soil erosion & landslides• Salinity, waterlogging• Floods, sediment movement• Coastal erosion & deposition

Water management • Surface water, groundwater• Quantity, quality• Environmental allocations, water re-use• land-use vs. water use

Geohazards

Earthquakes

Reactive soils

Volcanic eruptions

TsunamisFloods

Landslides and rockfalls

Karst and soluble rocks

Salinity and sodicity

Soil erosion

Coastal erosion

Sinkholes and collapsing soils

Acid sulfate soils

Contaminated soils

Permafrost

Geohazards – Volcanic hazards

Hawaii

Pyroclastic flowsLaharsGas emissionsDustClimate changesEnvironmental devastation

Geohazards – Volcanic hazards

Washington

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.

Japan11th March 2011

ML 9.020,448 dead

Canterbury, N.Z.2010 & 2011

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…)

Geohazards - Landslides

Wild Dog Road, 1979

Landslide mechanicsGeohazards - Landslides

Destabilising forces

Gravity

Water

Undercutting

Loads

Landslide mechanicsGeohazards - Landslides

Stabilising forces

Drain the slope

Retain the slope

Unload the slope

Anchor the slope

Landslide mechanics

Wild Dog Road, 1979

Barham Valley, 1986 Wongarra, 2000

Wild Dog Road, 1952

Geohazards - Landslides

48 Ha of mature forest slid into the 48 Ha of mature forest slid into the East Branch of the Barwon River inEast Branch of the Barwon River inLate June 1952, following heavy rain.Late June 1952, following heavy rain.

Forming a dam 400 metres wide and Forming a dam 400 metres wide and 30 metres high. 30 metres high.

Lake Elizabeth filledLake Elizabeth filled The top 26 metres of the dam was The top 26 metres of the dam was breached in August 1953 sending a breached in August 1953 sending a

7 metre wall of mud downstream.7 metre wall of mud downstream.

Geohazards - Landslides

Material removed to widen theMaterial removed to widen theGreat Ocean Road, 1968Great Ocean Road, 1968

Rock slide beginsRock slide begins

By 1971, 3000 tonnes of rock areBy 1971, 3000 tonnes of rock areSliding at 2cm per day. Sliding at 2cm per day. A further 150000 tonnes threaten A further 150000 tonnes threaten Movement.Movement.

Great Ocean Road closed July 1971Great Ocean Road closed July 1971Great Ocean Road opened December 1971Great Ocean Road opened December 1971

Cable anchorsCable anchorsinstalledinstalled

Geohazards - Landslides

Wongarra

Birregurra

Elliminyt

MoonlightHead

Geohazards - Landslides

Wye RiverWye RiverBoulevardeBoulevarde

Riverside DrRiverside Dr

Morley AvMorley Av Dunoon AvDunoon Av

Moorabool River 2001

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

Grampians National Park

2011

Grampians 2011

Geohazards - Rockfalls

Barwon Heads October 2000

Geohazards – Soil erosion by water & wind

Elaine

Wind erosion - Chinkapook

Sheet erosion - Morrisons

Tunnel erosion – Separation Creek

Gully erosion - Moreep

Erosion mechanics

Sheet erosion

Universal Soil Loss EquationAnnual soil loss (t/ha/yr)= Rainfall erosivity x soil erodibility x slope length x slope gradient x support practice factorx cover and crop management

Rill erosion

Channels < 0.3m depth

Gully erosion

Sediment transportWater flowHeadward erosion

Channels > 0.3m depth

Tunnel erosion

Soil aggregate stability(slaking and dispersion)

Geohazards – Soil erosion by water

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

Erosion impacts on waterways and wetlands

Illabarook

near Geelong

020406080

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Gullies

Landsl

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Sheet e

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Stream

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Erosion threat to roads. Number of erosion sites within 50 metre buffer.

Sealed Rd Unsealed Rd

St Paul, South Africa - donga

Ground subsidenceSinkholes, 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)

Karst processes

Example: Lake Peigneur, Louisiana1980 drilling causes a lake to drain into a salt mine(Google it and watch the video)

Dissolution of the aquifer

Limestone cavities result from dissolution of the aquifer by groundwater. The cavities grow larger over time and then collapse to form dolines.

Tropical storm “Agatha”

(May 29th – 30th 2010)

Sinkhole in Guatemala CitySunday May 30th 2010

Death toll 179 and rising

Landslides in El Salvador, Sinkhole in

Guatemala

20m diameter, 30m deep

Similar event February 2007

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)

Mexico City

Subsidence due to groundwater extraction threatens historic buildings such as the cathedral (1573 – 1813).

About 1m recent subsidencePlumb-bob to check restoration success

Old Basilica of Guadalupe (1531 – 1709)

Mexico City

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)

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

Geohazards – Acid sulfate soils

Tyrell Crk

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.

Summary

Landscapes are dynamic. Geohazards are natural processes

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

Geohazards can also be man-made (anthropogenic)

Port Campbell