There are fields along river banks called flood plains. They are called flood plains because in times of heavy rain when the water level rises in the river it overflows into the nearby fields or flood plains. When the heavy rain stopped the water receded back into the river. In Ireland during the boom when a lot of houses were built some of these houses were built on flood plains. So the houses that were built on flood plains got flooded during times of really heavy rain. Sometimes the flood plains were raised with stone & soil before building the houses so the new houses would not get flooded. But this resulted in the river bursting it banks further downstream probably in land that never used to get flooded in days gone by. I hope this makes sense!
There is also “groundwater flooding” which persists much longer than flooding through rainfall and rising rivers. Also, groudnwater flooding extends over a much larger area in Ireland, than any river flooding does.
Preventing groundwater flooding means understanding where/when/how floods occur, and just not build infrastructure in areas where flooding occurs (or elevate it, e.g. roads)
There are many factors that cause places to flood, and here is a list of them below. A key point in this list is heavy rain, urban drainage basins and not enough trees or plants. If you live in an area that is mostly concrete and very few plants.. nothing ill stop the water flowing. However, if there is grass, trees and plants, they take in the water into the soil and block the rain, the soil or other water sources act as basin or hole for the extra water to go too.
1. Heavy Rains
2. Rivers bursting because of too much water
3. Broken Dams
4. Urban Drainage Basins
5. Storm Surges and Tsunamis
6. Channels with Steep Sides
7. Not enough trees and plants
8. Snow and Ice melting
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