It does not have to rain to cause flooding. Floods can result from a number of other causes. These include:
Tsunamis such as the Indian Ocean Tsunami of 2004 can flood significant areas of low lying coastal areas with sea water. Flooding affects not only coastal areas but may extend along estuaries and coastal lakes and rivers some distance from the ocean. Flooding caused by tsunamis may carry very large amounts of debris.
Although dam failures are rare, their effects can be significant. Dam safety is monitored and some dams have early warning systems for communities that lie downstream of the dam and close to the dam. Should dam failure occur, significant downstream flooding with potentially swift flowing water and high amounts of debris can occur.
Sometimes pipelines carrying water can rupture causing localised flooding. The effects can range from minor inconvenience to significant releases of water that can erode roads and flood yards and houses.
Sea levels can be elevated above the highest high tide of the year due to the action of tropical and mid-latitude cyclones.
Under tropical and mid-latitude cyclones locally low pressure can cause sea levels to rise as there is less air pressing down on the sea. This is a particular problem with tropical cyclones where atmospheric pressures can be very low.
Persistent very strong onshore winds can result in the sea being 'piled up' against the shore locally raising sea levels and potentially flooding low lying coastal areas.