What is the SCS Curve Number?

What is the SCS Curve Number?

The SCS curve number method is a simiple, widely used and efficient method for determining the approxient amount of runoff from a rainfall even in a particular area. The curve number is based on the area’s hydrologic soil group, land use , treatment and hydrologic condition.

How do I find my CN number?

The weighted CN is calculated by taking the sum of each CN value multiplied by its fraction of the total subcatchment area. The sum is (usually) rounded to the nearest whole number, as described below. The rounded result is used for all calculations and reports.

What is SCS CN?

The Soil Conservation Service Curve Number (SCS-CN) method was developed in 1954 and is documented in Section 4 of the National Engineering Handbook (NEH-4) published by the Soil Conservation Service (now called the Natural Resources Conservation Service), U.S. Department of Agriculture in 1956.

What is the range of curve number?

has a range from 30 to 100; lower numbers indicate low runoff potential while larger numbers are for increasing runoff potential. The lower the curve number, the more permeable the soil is. As can be seen in the curve number equation, runoff cannot begin until the initial abstraction has been met.

What is SCS model?

Basic Concepts and Equations. The Soil Conservation Service (SCS) Curve Number (CN) model estimates precipitation excess as a function of cumulative precipitation, soil cover, land use, and antecedent moisture, using the following equation: Pe=(P−Ia)2(P−Ia)+S.

What is CN number?

“CN” means “combined nomenclature.” A CN code is a customs/tariff designation required in box 13 of export certificates for the EU. CN codes are published in the Official Journal of the European Union.

How does Arcgis calculate curve numbers?

In the Compute GIS Attributes dialog, select the SCS Curve Number option. Select the coverage or GIS layers to use for the calculation. Import the land use table file by clicking the Import button and selecting the land use table text file. Once your options are set, click OK to generate your curve numbers.

What is CN method?

The SCS-CN method predicts runoff from an expression for a rainfall-runoff curve that varies according to a single parameter called the curve number (CN). The dimensionless CN parameter describes the antecedent potential water retention of a watershed [Hawkins, 2014].

What is P in SCS?

P = potential maximum runoff (i.e., total rainfall if no initial abstraction). Example:Calculate the runoff depth for the 100 year storm event over the watershed with an average CN of 75 using the SCS Runoff Method. The design rainfall for 100 year storm event is 8.5 inches and drainage area is approximately 120 acres.

What is the full form of SCS?

SCS – Stabilization and Control System.