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Historical(1970-1980's)
2001
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Result:
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Elevation
 

Curve Number Analysis


Overview
The curve number was developed by the USDA Coil Conservation Service for Hydrological abstraction. The curve number varies from 1 to 100, being a function of the following runoff producing catchment properties: (1) Hydrological soil type,(2) land use and treatment, (3) ground surface condition, and (4) antecedent moisture condition. It is limited to the calculation of runoff depth and does not take into account temporal variations of rainfall variations. For un-gauged watersheds estimates of runoff curve numbers are given in tables.

More Resources on CN Analysis
Download CN Tables
Example of CN calculation and analysis

Your Task
Work with the Land Use data to calculate the Curve Number using the Runoff Curve Number tables. Download and open this WORD file and use it as a template to record your answers.

  1. Download a table showing land-use distribution areas in the watershed
  2. Using the CN tables, look up the corresponding CN for each type of Land Use type. Use the following translations: Forest –> Woods, Cropland –> Row Crops (SR), Shrubland –> Brush, Urban –> Residential 1/3 acre, and Pasture –> Open Space.
  3. Using the gathered CN, calculate the average CN for the watershed for the historical and 2001 data. Assume a Soil group “B” for all areas and soil condition is good.
  4. For storm Matthew, calculate the total rainfall depth in cm from rain gauge # 6.
  5. Based on the total rainfall calculated in the previous step, calculate the resulting runoff depth for both historical and 2001 conditions. Assume average AMC.
  6. If the antecedent condition was AMC I, what would be the runoff for both conditions?
  7. If the antecedent condition was AMC III, what would be the runoff for both conditions?

Once finished, click Next to continue.

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