In hydrology

Hydrology

Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...

, run-on refers both to the process whereby surface runoff

Surface runoff

Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

 infiltrates

Infiltration (hydrology)

Infiltration is the process by which water on the ground surface enters the soil. Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation. It is measured in inches per hour or millimeters per hour. The rate decreases as the soil becomes...

 the ground as it flows, and to the portion of runoff that infiltrates. Run-on is common in arid

Arid

A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...

 and semi-arid

Semi-arid

A semi-arid climate or steppe climate describes climatic regions that receive precipitation below potential evapotranspiration, but not extremely...

 areas with patchy vegetation

Vegetation

Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...

 cover and short but intense thunderstorms. In these environments, surface runoff is usually generated by a failure of rainfall to infiltrate into the ground quickly enough (this runoff is termed infiltration excess overland flow). This is more likely to occur on bare soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

, with low infiltration capacity. As runoff flows downslope, it may flow onto ground with higher infiltration capacity (such as beneath vegetation) and become run-on.

Run-on is an important process in the hydrological and ecohydrological

Ecohydrology

Ecohydrology is an interdisciplinary field studying the interactions between water and ecosystems. These interactions may take place within water bodies, such as rivers and lakes, or on land, in forests, deserts, and other terrestrial ecosystems...

 behaviour of semi-arid ecosystems. Tiger bush

Tiger bush

Tiger bush is a patterned vegetation community consisting of alternating bands of trees or shrubs, separated by bare ground or low herb cover, that run roughly parallel to contour lines of equal elevation...

 is an example of a vegetation community

Community

The term community has two distinct meanings:*a group of interacting people, possibly living in close proximity, and often refers to a group that shares some common values, and is attributed with social cohesion within a shared geographical location, generally in social units larger than a household...

that develops a patterned structure in response to, in part, the generation of runoff and run-on.