1. What is Parker's Formula?

Parker's Formula is an empirical equation used to estimate runoff depth from rainfall data, specifically designed for catchment areas in the Eastern United States. It provides a simplified method for calculating the portion of precipitation that becomes surface runoff.

2. How Does the Calculator Work?

The calculator uses Parker's Formula:

Where:

• \( RPRI \) — Runoff Depth in Inches
• \( RPI \) — Rainfall Depth in Inches

Explanation: The formula calculates runoff depth by multiplying rainfall depth by 0.80 and subtracting 16.5 inches, representing the portion of precipitation that becomes surface runoff.

3. Importance of Runoff Calculation

Details: Accurate runoff estimation is crucial for watershed management, flood prediction, urban planning, and designing drainage systems in Eastern US catchments.

4. Using the Calculator

Tips: Enter rainfall depth in inches. The value must be valid (greater than 0). The calculator will compute the corresponding runoff depth using Parker's Formula.

5. Frequently Asked Questions (FAQ)

Q1: What is the applicability range of Parker's Formula?
A: Parker's Formula is specifically designed for catchment areas in the Eastern United States and may not be accurate for other regions.

Q2: What are typical RPRI values?
A: Runoff depth values vary based on rainfall intensity, but typically range from a few inches to several inches depending on the rainfall event.

Q3: When should this formula be used?
A: This formula is best used for preliminary estimates in Eastern US catchments for urban planning and drainage design purposes.

Q4: Are there limitations to this formula?
A: The formula is empirical and may not account for all factors affecting runoff, such as soil type, land cover, and antecedent moisture conditions.

Q5: Should this be used for critical flood prediction?
A: For critical flood prediction and engineering design, more sophisticated hydrological models should be used in conjunction with this formula.