physical and human factors that effect flood risk

• heavy rainfall means water arrives too quickly for it to infiltrate in the ground, so there is a lot of surface runoff
• impermeable rocks dont allow infiltration so surface runoff is increased
• relief of land- water will run down the land faster so less infiltration
• buildings and roads are often made from impermeable materials, this increases surface runoff
• trees intercept rainwater on their leaves, which then evaporates. they also take up water from the soil and store it