Curve Number For Antecedent Moisture Condition One Calculator

Formula Used:

\[ CN = \frac{CN_{11}}{2.281 - 0.01281 \times CN_{11}} \]

Curve Number (CN):

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1. What is the Curve Number for AMC I?

The Curve Number for Antecedent Moisture Condition One (AMC I) is a hydrological parameter used to estimate direct runoff from rainfall. AMC I represents dry soil conditions where the soil has the maximum infiltration capacity.

2. How Does the Calculator Work?

The calculator uses the conversion formula:

\[ CN = \frac{CN_{11}}{2.281 - 0.01281 \times CN_{11}} \]

Where:

\( CN \) — Curve Number for AMC I
\( CN_{11} \) — Runoff Curve Number under AMC II conditions

Explanation: This formula converts the standard AMC II curve number to the corresponding value for dry soil conditions (AMC I), where the soil has higher infiltration capacity and lower runoff potential.

3. Importance of Curve Number Calculation

Details: Accurate curve number estimation for different moisture conditions is crucial for hydrological modeling, flood prediction, watershed management, and stormwater system design. AMC I represents the driest soil condition with maximum infiltration capacity.

4. Using the Calculator

Tips: Enter the standard AMC II curve number (CN11) value. The value must be a positive number greater than 0. The calculator will compute the corresponding curve number for dry soil conditions (AMC I).

5. Frequently Asked Questions (FAQ)

Q1: What are the three Antecedent Moisture Conditions?
A: AMC I (dry), AMC II (average), and AMC III (wet). AMC I represents the driest soil conditions with maximum infiltration capacity.

Q2: When should AMC I be used?
A: AMC I should be used when the watershed has been dry for 5 or more days preceding the storm, with total rainfall less than 1.3 cm in the previous 5 days.

Q3: How does AMC affect runoff calculations?
A: Drier conditions (AMC I) result in lower curve numbers, indicating higher infiltration capacity and less runoff for the same rainfall amount.

Q4: What is the typical range for curve numbers?
A: Curve numbers typically range from 30 (pervious surfaces) to 100 (impervious surfaces), with lower values indicating higher infiltration capacity.

Q5: Are there limitations to this conversion formula?
A: This empirical formula provides approximate conversions and may not be accurate for all soil types and land use conditions. Field verification is recommended for critical applications.