Natural Hazards: Australia and Japan

• Natural hazards include earthquakes, volcanic eruptions etc.

Natural Hazards Examples (Australia vs Japan)

• An earthquake with a magnitude of 5.9 struck a remote area of central Australia early on a Saturday morning.
• The quake's center was 460 kilometers west-southwest of Alice Springs, 10 kilometers deep, with no reported injuries or damage.
• A 6.4 magnitude earthquake hit Japan's southwestern island of Kyushu, heavily damaging Kumamoto Castle.
• Structures collapsed, water and electricity were cut off, and at least three people died with four hundreds injured.
• The earthquake caused loss of life and property

Natural Events

• When natural events occur in remote areas, they do not cause damage and are considered natural events.
• When natural events occur in populated areas and cause loss of life and property, they become natural hazards
• When natural hazards cause great loss of life and severe property damage, they become natural disasters.

Major Natural Hazards

• Tectonic hazards: earthquakes, volcanic eruptions, tsunamis
• Geologic hazards: Landslides
• Meteorological/Climatic hazards: typhoons, tornadoes, heat waves, cold surges, wildfire, floods, droughts
• Biological hazards: pests, infectious disease

Global Distribution of Volcanic Eruptions

• Volcanic eruptions have an uneven global distribution, occurring on continents and in oceans at any latitude.
• Volcanic eruptions form a linear pattern surrounding the Pacific Ocean.
• Isolated eruptions are found in the middle of the Atlantic Ocean.

Global Distribution of Earthquakes

• Earthquakes have an uneven global distribution, occurring on continents and in oceans at any latitude.
• Earthquakes form a linear pattern along plate boundaries.

Tropical Cyclones

• Tropical cyclones are also called typhoons.
• Typhoons are unevenly distributed and usually form over oceans in low latitudes.

Relief of Hong Kong

• Relief refers to the height, steepness, and shape of land.
• Hong Kong's relief is hilly, with many areas over 200 meters high, mainly composed of ranges of low hills.
• Over 60% of HK is made up of steep slopes.
• Natural lowland is limited, mainly located in river valleys and narrow coastal plains.
• Lowland areas: Yuen Long (largest extent), Kam Tin, and Fanling.
• Highest mountains: Tai Mo Shan, Lantau Peak and Sunset Peak

Coastline

• There are 263 islands in Hong Kong.
• Coastlines are long and irregular.

Map Skills

• Features on maps are represented by colouring and trigonometric stations.
• Other relief methods: contouring and spot height.
• Linear scales represent the ratio between actual and reduced size.
• Determining distance requires multiplying the scale ratio by map distance.

Vertical Exaggeration

• Vertical exaggeration - degree of enlargement of a cross-section.
• Ratio: Vertical Scale / Horizontal Scale.

Steepness of a Slope

• Identified by drawing a cross-section .
• Observing contour spacing: wide = gentle slope, close = steep slope
• Calculating gradient: Vertical distance / Horizontal distance.

Gradient of Slopes

• Steeper slopes have more closely spaced contour lines.

Map Scale

• Map scales can be linear, statement, or representative fraction types.
• Conversion between map scales is possible.

Measuring Curved Distances

• Involves marking straight paper segments, finding the actual distance on the map and adding them together.

Landslides

• Landslides - collapse of slopes where a mass of soil and rock rapidly descends, due to gravity.

Causes of Landslides

• Driving forces include slope gradient and weight of slope materials; greater force increases landslide risk.
• Resisting forces as shear strength includes cohesion and friction.
• Landslides when shear stress is greater than shear strength.

Landslides in Hong Kong

• Occur over an extensive area, close to built-up areas.
• Factors include natural (heavy rainfall, strong weathering, steep slopes) and human (cut slopes during construction, building roads and buildings, and removal of vegetation).
• Heavy rainfall increases weight and reduces friction and cohesion slope materials.
• Human activities increase slope destabilization.
• Broken slope cover and drainage channels allow water seepage, increasing weight.
• Hong Kong granite weathers easily, increasing loose materials.
• Hilly terrain with steep slopes raises landslide risk.

Effects of Landslides

• Landslides in built-up areas cause great damage.
• Loss of life and property occurs.
• Infrastructure as water pipes, gas pipes, and power lines can be damaged.
• Roads can be blocked due to material that has fallen.

Preventing Landslides

• Barriers: construction of flexible barriers or check dams.

Managing Slopes

• Engineering measures: plants, drainage channels, retaining walls, soil nails, shotcrete, weepholes, gabion walls.
• The Lands Department maintains man-made slopes records.
• The Geotechnical Engineering Office monitors and maintains slopes.
• Setup laws to restrict development on steep slopes.
• No slopes can be cut without careful study and government authorisation.
• Property owners are required to carry out proper slope maintenance measures.

Landslip Warning System

• The Hong Kong Observatory issues warnings when rainfall is heavy.
• Warnings alert the public to take precautions.

Education

• Educating the public to take appropriate actions when the landslip warning is in force.
• Provides well-trained rescue teams and emergency aid.
• Aid includes temporary shelters, financial aid and insurance.

Weather and Climate

• Weather - condition of the air around us over a short period.
• Seven elements of weather and climate: air temperature, wind direction, wind speed, air pressure, precipitation, relative humidity, and sunshine.
• Climate - average weather conditions over many years.

Measurement Units

• Air temperature: °C/°F
• Wind direction: E, S, W, N
• Wind speed: m/s
• Air pressure: Hectopascals (hPa)
• Precipitation: mm
• Relative humidity: %
• Sunshine: hours

Climate of Hong Kong

• Hot summer, with the highest mean monthly temperature at 29°C
• Cool winter, with the lowest mean monthly temperature at 16°C.
• The annual range of temperature is about 13°C
• The annual temperature is about 23.4°C.
• The annual high rainfall is about 2388 mm.
• Rainfall is uneven, and concentrated in summer.

Climate of Guangzhou

• Hot summer, with the highest mean monthly temperature at 28°C
• Cool winter, with the lowest mean monthly temperature is 14°C
• The annual average temperature is moderate, about 14°C
• The annual rainfall is high, about 1670mm / 1673mm
• Rainfall distribution is uneven, concentrated in summer

Climatic Characteristics of South China

• Four seasons, with unique characteristics for each.

Spring

• Mild, wet, and humid with foggy conditions.

Summer

• Hot, wet; typhoons and rainstorms are common

Autumn

• Warm, dry, and fine.

Winter

• Cool and dry

Monsoon Winds

• Monsoons change direction with the seasons.
• Eastern and southern China have a monsoon climate.

Summer Monsoon in Hong Kong

• Southwest winds that bring warm, moist, onshore air
• In summer, land absorbs heat faster than sea. Air therefore rises over the hot land surface.
• A low pressure system is formed over mainland China.

Winter Monsoon in Hong Kong

• Northeast winds, also call offshore winds, brings cool, dry weather.
• In winter, land releases heat faster than sea. Air therefore sinks over the cold land surface.
• A high pressure system is formed over mainland China.

Weather Symbols

• Used to describe precipitation, wind speed and direction
• Other symbols for fog or thunderstorms

Typhoon Characteristics

• Tropical storms, also known as tropical cyclones, are a low pressure system.
• Commonly developed in summer and in warm tropical waters.
• Most affect Hong Kong and other areas in the Philippines

Required Conditions To form a Typhoon

• Abundant supply of moist air.
• Warm water with surface temperatures over 26.5°C

Effects of Typhoons

• Includes strong winds, heavy rains, and storm surges.
• Causes deaths and injuries.
• Destroys buildings and crops.
• Triggers landslides.
• Flooding, damage power lines, traffic and disrupts economic activities.

Strategies for Storms

• Building typhoon-proof buildings and adopting better land use planning.
• Setting up monitoring and warning systems.
• Educating people to take precautionary actions.

Remedial Measures

• Support well-trained rescue teams and providing temporary shelters.