Geography - Flooding

Evaporation

when liquid water gets heated and turns in the gas - water vapour

Transpiration

when water used by trees + plants is released as water vapour from the leaves —→ air

Condensation

when water vapour cools and turns back into water

Precipitation

The water droplets get heavier + fall from sky as rain or snow

Infiltration

when water is absorbed by soil

Percolation

when some water sinks through rocks in the ground

Surface runnoff

When water flows on the ground into rivers

Throughflow

When water flows through soil

Groundwater flow

When water flows through rocks in the ground

Interception

When trees + plants’ leaves catch water, slowing its path to the ground

Permeable

When soil/rock allows water to pass

Impermeable

When soil/ rock doesn’t allow water to pass

Saturated

When the pores are full of water

Causes of flooding

urban sprawl, deforestation, heavy/ prolonged rainfall, steep slopes, impermeable rock

Urban sprawl

less permeable surfaces —→ less infiltration, more surface water, more surface runnoff + channels water faster

Deforestation

fewer trees —→ less interception + transpiration, water hits soil faster, increased infiltration, saturated quicker , more surface runnoff

Heavy/ prolonged rainfall

more infiltration in less time, saturated faster, more surface runoff

Steep slope

more influence from gravity, less infiltration, less water stored in soil, more surface runoff

Impermeable rock

still infiltration, no percolation, saturated soil above, more surface runoff

Hard engineering

Human made, artificial structures + actions that works against nature

Soft engineering

Adaptations that work with nature

Increased flood risk

• Climate change → more rainfall & rising sea levels

• Risk from rivers and coasts

More people at risk

Building on floodplains due to land shortage

Higher costs & pressure

• Expensive materials and planning

• Public demand for action

dams + reservoirs (description)

water trapped behind (resevoirs)
water released in controlled way

dams + reservoirs ( positive)

• can produce HEP

• can attract tourists (water sports)

• can be used to manage water for domestic + agriculture uses

dams + reservoirs (negative)

• habitats flooded —→ rotting vegetables —> releases methane

• traps sediment (affects rivers as a whole)

• people displaces - settlements lost

• very expensive

dredging (description)

• removes sediment from bottom of river

• creates more room of water in river (deeper + wider)