Hydrological Hazards

Term Level Definition Source
Hydrological hazard Subgroup A hazard caused by the occurrence, movement, and distribution of surface and subsurface freshwater and saltwater. IRDR
Flood Type Subtype (General) A general term for the overflow of water from a stream channel onto normally dry land in the floodplain (riverine flooding), higher-than-normal levels along the coast (coastal flooding) and in lakes or reservoirs as well as ponding of water at or near the point where the rain fell (flash floods). IRDR
Coastal flood Subtype Higher-than-normal water levels along the coast caused by tidal changes or thunderstorms that result in flooding, which can last from days to weeks. IRDR
Flash flood Subtype Heavy or excessive rainfall in a short period of time that produces immediate runoff, creating flooding conditions within minutes or a few hours during or after the rainfall. IRDR
Riverine flood Subtype A type of flooding resulting from the overflow of water from a stream or river channel onto normally dry land in the floodplain adjacent to the channel. IRDR
Ice jam flood Subtype The accumulation of floating ice restricting or blocking a river’s flow and drainage. Ice jams tend to develop near river bends and obstructions (e.g., bridges). IRDR
Mass movement (wet) Type Types of mass movement that occur when heavy rain or rapid snow/ice melt send large amounts of vegetation, mud, or rock down a slope driven by gravitational forces. IRDR1
Avalanche (wet) Subtype A large mass of loosened earth material, snow, or ice that slides, flows, or falls rapidly down a mountainside under the force of gravity. Snow Avalanche: Rapid downslope movement of a mix of snow and ice. IRDR
Landslide (wet) Subtype Any kind of moderate to rapid soil movement incl. lahars, mudslides, and debris flows (under wet conditions). A landslide is the movement of soil or rock controlled by gravity and the speed of the movement usually ranges between slow and rapid, but it is not very slow. It can be superficial or deep, but the materials must make up a mass that is a portion of the slope or the slope itself. The movement has to be downward and outward with a free face. EM-DAT
Rockfall (wet) Subtype
Sudden subsidence (wet) Sinking of the ground due to groundwater removal, mining, dissolution of limestone (e.g., karst sinkholes), extraction of natural gas, and earthquakes. In this case, the sinking occurs under wet conditions as a result of a hydrological trigger (e.g., rain). IRDR2
Mudslide Subtype
Wave action Type Wind-generated surface waves that can occur on the surface of any open body of water such as oceans, rivers, or lakes. The size of the wave depends on the strength of the wind and the distance traveled (fetch). IRDR
Rogue wave Subtype An unusual single crest of an ocean wave far out at sea that is much higher and/or steeper than other waves in the prevailing swell system. IRDR
Seiche Subtype A standing wave of water in a large semi- or fully-enclosed body of water (lakes or bays) created by strong winds and/or a large barometric pressure gradient. IRDR

  1. The “Mass movement (wet)” definition is adapted from the IRDR definition of “Debris flow, mud flow, rock fall”. ↩︎

  2. The first definition sentence of “Sudden subsidence (wet)” is the definition of “Subsidence” in the IRDR glossary. The second sentence has been added to distinguish this class from “Sudden subsidence (dry)” in the geophysical group. ↩︎