How do you find the direct runoff from the unit hydrograph?

How do you find the direct runoff from the unit hydrograph?

For example, if a rainfall of P1 inches occurs during a time interval of Δt, the total runoff hydrograph is P1 multiplied by the total unit hydrograph, which is the blue curve (PUH_1) in the figure below. If the rainfall stops after Δt, this is the direct runoff hydrograph.

How do you calculate runoff?

Simple, straightforward methods of calculating runoff can tell you the amount of water that storms bring to the earth. For a given surface area such as a roof or yard, multiply the area by the inches of rainfall and divide by 231 to obtain the runoff in gallons.

What is unity in unit runoff hydrograph?

In a unit hydrograph, the depth of rainfall excess must be unity and the ordinates must be positive. Unit hydrograph ordinates are in terms of intensity of rainfall excess on a discharge per unit catchment area basis, the unit area thus representing the unit rainfall excess.

What is runoff hydrograph?

A runoff hydrograph represents the cumulative runoff resulted from surface and sub-surface (base flow) runoff. The surface runoff or direct runoff hydrograph is obtained from the total storm hydrograph by separating the base flow.

What is relation between rain and runoff?

the rainfall-runoff relationship for any rainstorm depends on the dynamic interaction between rain intensity, soil infiltration and surface storage. Runoff occurs whenever rain intensity exceeds the infiltration capacity of the soil, providing there are no physical obstructions to surface flow.

What is direct run off?

Direct surface runoff is the rain or meltwater that runs off during the rain or melt event as overland flow or in the vegetation cover above a frozen soil. The meltwater and the rain falling onto snow or on frozen ground reach a stream along different pathways.

What is effective runoff?

Effective rainfall (or precipitation) is equal to the difference between total rainfall and actual evapotranspiration. At ground level, water from effective rainfall is split into two fractions: surface run-off and infiltration.

What are the factor affecting runoff?

Meteorological factors affecting runoff: Rainfall intensity. Rainfall amount. Rainfall duration. Distribution of rainfall over the watersheds.

What are the elements of runoff?

Factors Affecting Runoff:

  • Rainfall pattern: If the rainfall is very heavy the consequent runoff will also be more.
  • Character of catchment surface: ADVERTISEMENTS:
  • Topography:
  • Shape and size of the catchment:
  • Vegetal cover:
  • Geology of the area:
  • Weather conditions:

How do you reduce runoff?

What can you do to reduce the runoff from your property?

  1. Disconnect/Redirect Downspouts.
  2. Use a rain barrel to capture rain from your roof.
  3. Plant a rain garden.
  4. Plant trees.
  5. Reduce impervious surfaces; install permeable pavement.
  6. Plant a green roof.

What are three types of runoff?

There are three major types of runoff depending on the source: surface flow, interflow, and base flow.

What do you mean by runoff?

Runoff, in hydrology, quantity of water discharged in surface streams. Runoff also includes groundwater that is discharged into a stream; streamflow that is composed entirely of groundwater is termed base flow, or fair-weather runoff, and it occurs where a stream channel intersects the water table.

What is the relationship between infiltration and surface runoff?

The terms, surface runoff and infiltration, which form the title of this paper, are usually associated with a piece of land and the precipitation falling upon it. They suggest that this ground is porous, that part of the water will infiltrate into it while the rest runs off along the surface or evaporates.

What comes first runoff or infiltration?

Infiltration occurs when surface water enters the soil. At this point, the soil becomes saturated, but the excess water has to go somewhere. When this happens, we get overflow in the form of runoff, which is when surface water flows over land.

How do you prevent surface runoff?


  1. Mulch Farming.
  2. Soil Conditioners.
  3. Cover Crops.
  4. Alley Cropping.
  5. No-tillage Farming.
  6. Ploughing.
  7. Strip Cropping.
  8. Contour Farming.

How do you control infiltration?

One way to control building infiltration is to offset outdoor air intentionally brought into the building from the exhaust air. With this slight pressurization, a calculated amount of air leaks out of the building to prevent potentially humid outside air from entering the building.