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Definitions of Events



Water that overflows rivers or streams and runs slowly or quickly on small or large areas.

Urban Flood

Storm water that gets collected in city or urban areas after heavy rains due to blocking or under capacity of storm water drains.


The sudden overflowing of a river; or violent water flow in a river or stream; or unexpected violent water flow on drainage path or land. Flash floods can be caused by rain; a reservoir dam overflowing / bursting / breaching; or abundant landslides on a watershed or basin. Flash-floods usually carry tree trunks and/or fine to bulky sediment.


  • On land - This can be a surge of water mass due to overflowing or breach of a reservoir dam. This would be synonymous with flash floods.
  • Sea surge - Sea tides breaking on the shore and flooding the coastal areas. Can result in erosion of beaches and sand banks.


All mass movements other than surface erosion of a hillside. This event includes terms such as precipitation of earth, settling, horizontal land thrust, mass movement, displacement and detachment of soil masses on watersheds or hillsides.

The following can be identified as separate events:
  • Rock falls - Movement of rock on hillside or watersheds slowly or rapidly.
  • Land subsidence - Subsidence, collapse of caves or mines due to a vacuum / void formed under the ground surface naturally or as a result of human activities
  • Cutting failures –
  • Retaining wall failures -