1. Mitigation measures
1.1. Regulation (a law)
1.1.1. Zoning
1.1.1.1. How the government plans its development of the land
1.1.1.2. Flood-prone areas: reserved for Low-value developments like Parks and fields
1.1.1.3. Fewer casualties and less economic losses
1.1.1.4. Example: Minnesota, Minnesota river is surrounded by Parks, residential areas are further away
1.1.2. Elevated properties
1.1.2.1. Elevate or raise properties to a certain height
1.1.2.2. Minimum Platform Level (MPL): minimum ground level for a development
1.1.2.3. Development is protected against floods because of the elevated flood
1.1.2.4. But need to add slope and stairs, increased cost of development
1.2. Investment in infrastructure
1.2.1. Levees and floodwalls
1.2.1.1. Barriers against floods and protect the developments from floodwater
1.2.1.2. Levees: raised river banks
1.2.1.3. Floodwalls: man-made structures to keep out the floodwater
1.2.1.4. Example: flood-prone city of Sacramento builds kilometres of levees along the Sacramento River to protect surrounding land from floods
1.2.2. Channel improvement
1.2.2.1. Increase the capacity of a water body to hold water
1.2.2.2. Canals and river channels can be widened and deepened to carry more water
1.2.2.3. Or straightened so water can be drained away quickly
1.2.2.4. Example: expansion of Bukit Timah canal to increase channel capacity, allowing moderate to high-value developments LIKE NYGH to be built along the Cana
1.3. Disaster preparedness
1.3.1. Forecasting and warning system
1.3.1.1. Cities monitor the water levels in water bodies
1.3.1.2. Detect when the water level is exceeding the water body, about to overflow
1.3.1.3. Flood warnings will be issued to public in the event of a flood
1.3.1.4. Weather forecast: look at weather conditions, predict if a flood might occur
1.3.2. Evacuation drills
1.3.2.1. Plan to evacuate a large number of people in the shortest time
1.3.2.2. Purpose: raise awareness among the people, reduce panic during an actual flood as they are more prepared
1.3.2.3. Hence reduce the number of casualties as people are aware of how to evacuate
1.3.3. Public advisory
1.3.3.1. What to do in the event of a flood?
2. Effects of floods
2.1. SOCIAL impacts
2.1.1. Injuries, diseases, deaths
2.1.1.1. Debris and random "things" washed by the fast-moving floodwaters, cause people to be injured
2.1.1.2. Water-borne diseases eg cholera
2.1.1.3. Water is contaminated
2.1.1.4. Puddles of stagnant water, mosquitoes breed - dengue :(
2.1.1.5. Floods cause buildings to collapse, cause casualties
2.1.2. Disruption to water supply
2.1.2.1. Sewage pipes burst, sewage spills out and contaminates the water
2.1.2.2. No clean water, people cannot consume the water
2.1.2.3. No water supply to run the machines
2.1.3. Houses washed away
2.1.3.1. Floodwaters cause damage to property, sweep houses away
2.1.3.1.1. Case study: Hurricane Katrina, nearly 1.5 million people in New Orleans were displaced or left homeless
2.1.3.2. Evacuate to shelters
2.2. ECONOMIC impacts
2.2.1. Damage of machines
2.2.1.1. Equipment submerged in water; cause damage to motors and electrical components
2.2.1.2. Factories cannot operate at full capacity; economic losses
2.2.1.3. Example: 2011 Thailand floods, industrial Parks flooded, factories cannot operate and people lose their jobs - extensive damage to manufacturing industry
2.2.2. Disruption to transport infrastructure
2.2.2.1. During a flood: infrastructure submerged or damaged, becomes impassable
2.2.2.2. A lot of time and money needed to repair the damaged infrastructure
2.2.2.3. Example: 2014 heavy rain in Bosnia, destroying roads and bridges, slowing down rescue and relief works
2.2.3. Disruption to energy supply
2.2.3.1. Affect distribution of supply of energy
2.2.3.2. Flooded road conditions - trucks cannot transport gasoline from terminals to gas stations
2.2.3.3. Power lines damaged - power outages
2.2.3.4. Lack of electricity: factories and anything cannot operate
2.3. PSYCHOLOGICAL impacts
2.3.1. Stress from loss of loved ones
2.3.1.1. Emotional distress
2.3.1.2. Example: adults who have experienced floods more likely to suffer from depression and anxiety
2.3.2. Loss of belongings
2.3.2.1. Items washed away by floodwater can be things the people greatly treasure
2.3.2.2. Even the house can hold a special meaning, rebuilding cannot bring back the memories of the house
2.3.3. Loss of a home - stress of rebuilding a new one
2.3.3.1. Cost involved
2.4. ENVIRONMENTAL impacts
2.4.1. Soil erosion
2.4.1.1. Floodwater washes the soil away, into the water bodies
2.4.1.2. Leads to potential water pollution
3. New node
3.1. Height of land above sea level
3.1.1. Mean sea level: average height of the sea surface
3.1.2. Below sea level: more prone to floods
3.2. Proximity to water bodies
3.2.1. Cities nearer water bodies: more prone to floods
3.2.2. Or cities with rivers running through them
3.3. Permeability of surface cover
3.3.1. Vegetated surfaces - more permeable, water can infiltrate ground more easily
3.3.2. Concrete surface - higher surface runoff
3.3.3. Higher proportion of impermeable surfaces - more prone to floods
3.4. Channel capacity
3.4.1. Volume of water that can be held in a water body without overflowing
3.4.2. Why floods occur? Too much rainfall, capacity of the channel is exceeded
3.4.3. City has high proportion of built-up areas; needs to drain water away quickly
4. New node
5. New node
5.1. SOCIAL impacts
5.1.1. Injuries, spread of diseases, loss of lives
5.1.1.1. Injured by objects and debris washed along by fast-moving floodwater
5.1.1.2. Floods cause buildings to collapse - result in casualties
5.1.1.3. Caught in the flood: suffer from hypothermia
5.1.1.3.1. Constant shivering
5.1.1.3.2. Confusion
5.1.1.4. Water-borne diseases spread, water supplies contaminated by chemical spills
5.1.1.5. Water puddles cause mosquitoes to breed - dengue
5.1.2. Homelessness
5.1.2.1. Floods: damage property, sweep houses away
5.1.2.2. Victims evacuate to emergency shelters
5.1.2.3. Cities most affected: high population density, most houses washed away
5.1.3. Disruption to clean water supply
5.1.3.1. Damaged water pipes
5.1.3.2. Sewage pipes burst - contaminate water supplies
5.1.3.3. Water supply and sanitation facilities are affected
5.2. ECONOMIC impacts
5.2.1. Damage to machinery / equipment
5.2.2. Damage to transport infrastructure
6. Types of floods
6.1. Coastal flood
6.1.1. Tropical storms
6.1.1.1. A lot of rain
6.1.1.1.1. New node
6.1.2. Tropical cyclones
6.1.2.1. Typhoon
6.1.2.2. Hyrricane
6.1.3. Storm surges
6.1.3.1. Strong wind
6.1.3.2. Large waves
6.1.4. Tsunamis
6.1.4.1. Huge ocean waves
6.1.5. New node
6.2. River flood
6.2.1. Water in the river overflows
6.2.1.1. Snowmelt (snow melting from mountains)
6.2.1.2. Heavy rainfall (too much for the river)
6.2.1.3. Dam failure (china dam always fails)
6.2.1.4. Too much
6.2.2. Low-lying land around the river
6.3. Flash flood
6.3.1. Heavy rainfall
6.3.1.1. Short period of time
6.3.1.2. Quick rise in water level
7. Causes of floods
7.1. Rainfall
7.1.1. Rainfall intensity
7.1.1.1. Rate at which rain falls
7.1.1.2. High rainfall intensity: a lot of rain
7.1.2. Rainfall duration
7.1.2.1. Duration of the rain
7.1.3. Rainfall frequency
7.1.3.1. Probability of occurrence of a certain amount of rain falling within a certain period of time
7.2. Snowmelt
7.2.1. Surface runoff from melting snow
7.2.2. - temperate countries
7.2.3. - spring season, when temperature increases
7.3. Storm surge
7.3.1. During a storm
7.3.2. Strong winds push water towards the coast
7.3.3. High tides, water piled up against coastline beyond normal conditions
7.4. Failure of man-made structures
7.4.1. Example: dams and levees
7.4.2. Dam failure: amount of water cannot be regulated, areas downstream will be flooded