1. Human-made Causes
1.1. Deforestation
1.1.1. The large area of trees being cutdown reduces the interception from the trees
1.1.2. Also reduces the rate of infiltration into the soil
1.2. Cultivation
1.2.1. Some cultivation method can lead to increase water flow
1.3. Urbanisation
1.3.1. Building materials like concrete and tarmac are impermeable, meaning water cannot go through it
1.3.2. Man made buildings like dams can cause a jam in the rivers and when dams rapture are large amount of water gets overboard
1.4. Climate change
1.4.1. The unpredictable weather patterns caused by climate change can cause flooding
1.4.1.1. Unexpected drought
1.4.1.2. Unexpected snow
1.4.1.3. Unexpected tropical cyclones
1.4.1.4. Unexpected heavy rianfall
2. Flood prevention
2.1. Stormwater pumps
2.2. Improved stormwater drainage systems
2.3. Levees and dams
2.4. Tide and flood gates
2.5. Sea walls and flood walls
2.6. Education and awareness
2.7. Flood control measures
2.8. Improved urban planning
3. Flooding occurs when a discharge of a river exceeds the capacity of the river's channel.
4. Natural Causes
4.1. Prolonged rainfall
4.1.1. Saturates the soil
4.1.1.1. Less water being able to infiltrate the soil
4.1.2. Causes water table to rise, reducing infiltration capacity
4.2. Heavy rainfall
4.2.1. Could reduce the amount of water being infiltrated into the soil
4.2.2. Could overflow the river if the heavy rain was above the river
4.3. Saturated soil
4.3.1. The more saturated the soil, lesser infiltration and more overland flow
4.3.2. Less water infiltrating the soil will lead to a build up of water above the ground
4.4. Snowmelt
4.4.1. The snow that fell on soil can hold rainfall for a long period of time rather than it infiltrating into the soil
4.4.2. When these snow melt, the amount of water stored in the snow is too much for the soil to hold
4.4.2.1. Resulting in the excess water running off into a river/stream and overflowing it
4.5. Ice/debris jam
4.5.1. The ice and debris jams the river/stream when they fell in them causing the river to overflow
4.5.1.1. Ice jams are often resolved when the ice melts
4.5.1.2. With the case of debris jam, the options are to take measures remove them or to wait for the debris to break free
4.5.1.3. They also have an affect to economic and ecological implications
4.6. Earthquakes
4.6.1. The aftershock of the earthquakes can cause tsunamis
4.6.1.1. Tsunamis are series of giant waves caused by the displacement of large volume of water
4.6.1.2. These series of large waves can flood habitants who live near coasts
4.7. Tropical cyclones
4.7.1. Storm surges
4.7.1.1. an abnormal rise of water generated by a storm
4.7.1.2. causes large amount of water to be brought inland by the heavy winds of the storms