What do you mean by overland flow?

Overland flow is water that runs across the land after rainfall, either before it enters a watercourse, after it leaves a watercourse as floodwater, or after it rises to the surface naturally from underground.

What is the difference between channel flow and overland flow?

Overland flow is surface runoff that occurs in the form of sheet flow on the land surface without concentrating in clearly defined channels. This type of flow is the first manifestation of surface runoff, since the latter occurs first as overland flow before it has a chance to flow into channels and become streamflow.

How is overland flow measured?

Measuring overland flow Overland flow can be assessed using a length of plastic guttering. Choose a 50cm or 1m long length, with both ends closed. Bury the guttering just in the soil so that the upper edge is parallel with the soil surface. Cover the open top of the gutter with a plastic cover to keep out the rain.

What is overland flow and interflow?

Saturation excess overland flow occurs when the soil is saturated and no more rain or snowmelt can infiltrate. Interflow is the subsurface movement of water to the stream and can be a significant component of runoff.

What causes overland flow?

when the intensity of precipitation that reaches the surface exceeds the infiltration capacity of the soil. This process is known as Hortonian overland flow. 2. when the combination of precipitation intensity and duration (and run-on from higher areas) saturates the soil and raises the water table to the surface.

What affects overland flow?

Meteorological factors affecting runoff:

  • Type of precipitation (rain, snow, sleet, etc.)
  • Rainfall intensity.
  • Rainfall amount.
  • Rainfall duration.
  • Distribution of rainfall over the watersheds.
  • Direction of storm movement.
  • Antecedent precipitation and resulting soil moisture.

What is the difference between surface runoff and overland flow?

Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil.

Why does overland flow happen?

Saturation Excess Overland Flow occurs when the soil becomes saturated, and any additional precipitation or irrigation causes runoff. This type of runoff is the main mechanism behind VSA hydrology.

How can overland flow be reduced?

A suite of best management practices for reducing overland flow may include actions to increase surface roughness and canopy interception, maintain soil porosity, and otherwise disperse concentrated or fast-moving flows of water.

What is length of overland flow?

The length of overland flow (Lg or AOLF) Length of overland flow is a length of water over the ground before it gets concentrated into certain stream channels. Lg = 1/(Dd X 2), where Dd (drainage density) is in km/km2. Length of overland flow is mentioned with other term, i.e., average over land flow (AOLF) [4].

What increases overland flow?

Infiltration-excess overland flow develops when the rate of water input on the land surface is higher than the infiltration rate. It is common in arid regions with limited vegetation, particularly where soils are thin, and rainfall intensities are high.

What is overland flow?

Overland flow is defined as water that flows over the land surface as either diffuse sheet flow (laminar or mixed laminar flow) or concentrated flow (turbulent flow) in rills and gullies (Ward and Robinson, 2000). T.S. Steenhuis, M.T. Walter, in Encyclopedia of Soils in the Environment, 2005

What is the maximum length of overland flow on a slope?

not designated as highly erodible, a maximum length of overland flow of 200 feet may be used. Highly erodible soils are designated as United States Department of Agriculture Natural Resources Conservation Service land capability classification (LCC) classes IIIe, IVe, VI, VII, or

How does overland flow affect water pollution?

Since increased overland flow means that more of the water will be exposed to the land surface where potential pollutants tend to accumulate, these modifications greatly exaggerate the risk of chemical contamination or biogeochemical loading to surface water bodies.

What is the relationship between flow velocity and flow volume?

For example, larger flows and flow volumes are directly related to higher flow velocities, which cause erosion and channel incision, and also may disconnect the channel from the riparian zone.