New disasters flood definition Riverine flooding includes: • overflow from river channel or river floods • flash floods • alluvial fan floods • ice-jam floods • dam-break floods There is often no sharp distinction between river floods, flash floods, alluvial fan floods, ice-jam floods, and dam-break floods that occur due to structural failures or overtopping of embankments during flood (or other such as landsliding, rockfalling, etc.) events. Nevertheless, these types of floods are widely recognised and helpful in considering not only the range of flood risk but also appropriate emergency preparedness and responses. In general, the river floods are caused either by rainfall of extra-tropical or frontal character, as experienced in temperate latitudes, or by large tropical atmospheric depressions with moisture-laden winds, moving from a maritime environment onto and across a land mass (for instance, seasonal monsoons in Asia and line squalls on the west coast of Africa). Rainfall in these events is generally widespread and can be heavy. The level of flooding can be high, and is influenced by topographic features.