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Curve Number Formula:
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The Curve Number for Antecedent Moisture Condition-III (AMC-III) is a hydrological parameter used to estimate direct runoff from rainfall. It represents the soil's moisture condition when the soil is nearly saturated from previous rainfall events.
The calculator uses the Curve Number formula:
Where:
Explanation: This formula converts the standard AMC-II curve number to the corresponding value for wet antecedent moisture conditions (AMC-III).
Details: Accurate Curve Number estimation is crucial for hydrological modeling, flood prediction, watershed management, and designing drainage systems. The AMC-III condition represents the worst-case scenario for runoff potential.
Tips: Enter the standard AMC-II Curve Number value. The value must be greater than 0 and typically ranges between 30-100 for most land use and soil conditions.
Q1: What are the different Antecedent Moisture Conditions?
A: AMC-I: Dry conditions, AMC-II: Average conditions, AMC-III: Wet conditions. Each represents different soil moisture levels before a rainfall event.
Q2: When should AMC-III be used?
A: AMC-III should be used when the watershed has received significant rainfall in the preceding 5 days, making the soil nearly saturated.
Q3: What is the typical range for Curve Numbers?
A: Curve Numbers typically range from 30 (pervious surfaces) to 100 (impervious surfaces), with higher numbers indicating greater runoff potential.
Q4: How does AMC affect runoff calculations?
A: Wet conditions (AMC-III) result in higher Curve Numbers and consequently higher runoff estimates compared to dry conditions (AMC-I).
Q5: Can this calculator be used for all soil types?
A: Yes, the conversion formula applies to all hydrologic soil groups, though the input CN11 should be appropriate for the specific soil and land use conditions.