Editing Flood (section)

=== Areal flooding ===
[[File:House surrounded by flood Ilmajoki Finland.jpg|thumb|In spring time, the floods are quite typical in [[Ostrobothnia (historical province)|Ostrobothnia]], a flat-lying area in [[Finland]]. A flood-surrounded house in [[Ilmajoki]], [[South Ostrobothnia]].]]
Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can either [[Infiltration (hydrology)|infiltrate]] or [[Surface runoff|run off]]. The excess accumulates in place, sometimes to hazardous depths. Surface [[soil]] can become saturated, which effectively stops infiltration, where the [[water table]] is shallow, such as a [[floodplain]], or from intense rain from one or a [[storm train|series of storms]]. Infiltration also is slow to negligible through frozen ground, rock, [[concrete]], paving, or roofs. Areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of [[Surface runoff|overland flow]] depends on the surface slope. [[Endorheic basin]]s may experience areal flooding during periods when precipitation exceeds evaporation.<ref>{{cite book|last1=Jones|first1=Myrtle|title=Fact Sheet|chapter=Ground-water flooding in glacial terrain of southern Puget Sound, Washington|chapter-url=https://pubs.er.usgs.gov/publication/fs11100 |date=2000|doi=10.3133/fs11100|access-date=2015-07-23|ref=MJones}}</ref>