What are Floodplain Types?

Riverine Floodplains

• Riverine floodplains are usually defined as wide, flat areas that lie adjacent to a river, creek, lake or coastline. Riverine flooding can inundate the plain for days or weeks. The water covering a riverine floodplain is generally shallow, but it can rise if rains continue to fill a river channel hundreds of miles upstream.

Mountainous Floodplains

• Mountainous floodplains are frequently located within ranges characterized by steep river valleys or a peak that has eroded into an alluvial fan. Floods in these areas are often of the "flash" variety, occurring with little warning. Mountainous floodplains may be decimated by walls of debris-filled water which possess incredible force but are of short duration.

Estuarine Floodplains

• Estuarine floodplains are the areas lying between the mouth of a river and an ocean. Bays, harbors, sounds, inlets and marshlands are estuaries. Estuarine floodplains are usually submerged when tides suddenly rise and a storm surge takes place, as in the case of hurricanes or cyclones.

Periodic Floodplains

• Periodic floodplains are categorized by names such as "100-year" floodplain. The statistical reference does not mean that a gigantic flood will happen every 100 years. It instead refers to the idea that there is a one in 100 chance, in any given year, that a specific land area will be covered by a certain amount of water. Periodic floodplains may rarely experience flooding, but when they do, the results can be catastrophic.

Coastal Floodplains

• Coastal floodplains are the areas bordering an ocean or large lake. These areas generally are afflicted with rising waters stemming from storm surges or hurricanes and are not protected by an estuary. Loss of life can be extreme when a coastal floodplain experiences a natural disaster, as was the case with the Indian Ocean earthquake and tsunami that crippled Thailand in 2004.