The border across which genes can flow between two populations is called the contact zone. Natural selection operates to produce changes in populations.

Through flow is the horizontal movement of water through the soil zone.

Groundwater flow is the movement of water through the bedrock, which is typically an aquifer

Longshore currents

Richard G. Niswonger has written:

'Documentation of the Unsaturated-Zone Flow (UZF1) Package for modeling unsaturated flow between the land surface and the water table with MODFLOW-2005' -- subject(s): Computer simulation, Zone of aeration, Groundwater flow, Percolation

Water flow alarm is an alarm activated by a water flow, typically from a sprinkler head. Some jurisdictions require a separate monitoring zone for water flow, as waterflow alarms are less likely to be activated accidentally.