Floods occur when the ground becomes saturated from heavy rain and can no longer absorb water, causing the water to remain on the surface and flow into rivers and seas. Severe storms can also cause rivers to overflow their banks, spilling water onto surrounding lands and creating devastating floods. Floods are the most common and costly natural disasters, responsible for around 90% of all natural disaster damage. Proper management of runoff and absorptive ground is needed to prevent flood waters from overflowing onto property.