Runoff

Runoff is water that flows over land or through shallow subsurface pathways toward streams and other water bodies. It moves precipitation and snowmelt from landscapes into drainage networks.

Infiltration: The movement of water from the land surface into soil or porous rock. Water that infiltrates is less immediately available for overland flow.
Precipitation: Water released from the atmosphere as rain, snow, sleet, or hail. It is the main input that can become runoff.
Flash flood: A rapid flood that develops over a short time, often after intense rain. A sudden surge of runoff can produce dangerous flooding in streams and urban areas.
Streamflow: The movement of water through a river or stream channel. Runoff from a drainage area contributes to streamflow and its variation.
Groundwater recharge: The downward movement of water that replenishes groundwater stores. Recharge carries water into aquifers rather than directly toward surface channels.
Saturation-excess overland flow: Surface runoff produced when rainfall lands on soil already saturated with water. This process generates runoff where the soil can no longer store additional water.
Soil moisture: The amount of water held in soil pores at a given time. It affects how much incoming water can infiltrate before runoff forms.
Flood forecasting: The prediction of flood timing, extent, or severity using observations and models. Runoff estimates help forecast streamflow peaks and flood hazards.
Sediment transport: The movement of mineral and organic particles by flowing water, wind, ice, or gravity. Runoff carries eroded particles into channels and downstream environments.
Interception (hydrology): The capture of precipitation by vegetation or other surfaces before it reaches the ground. Interception delays or reduces the water available to become runoff.

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