1. What is the Runoff Depth Formula?

The Runoff Depth formula calculates the amount of water that flows over land surfaces rather than infiltrating into the soil. It is derived from the relationship between rainfall depth, infiltration rate, and rainfall duration.

2. How Does the Calculator Work?

The calculator uses the Runoff Depth formula:

Where:

• \( R \) — Runoff Depth (mm)
• \( P_{cm} \) — Rainfall Depth (mm)
• \( W \) — W-Index (m/s)
• \( t_r \) — Rainfall Duration (s)

Explanation: The formula subtracts the infiltrated water (W-Index multiplied by rainfall duration) from the total rainfall depth to determine the runoff depth.

3. Importance of Runoff Depth Calculation

Details: Accurate runoff depth estimation is crucial for hydrological modeling, flood prediction, water resource management, and designing drainage systems.

4. Using the Calculator

Tips: Enter rainfall depth in mm, W-Index in m/s, and rainfall duration in seconds. All values must be non-negative.

5. Frequently Asked Questions (FAQ)

Q1: What is W-Index?
A: W-Index refers to the uniform rate of infiltration during a rainstorm after initial infiltration capacity has decreased, typically measured in cm/h or m/s.

Q2: How is rainfall depth measured?
A: Rainfall depth is typically measured using rain gauges that collect and measure the amount of precipitation over a specific period.

Q3: What factors affect runoff depth?
A: Soil type, land cover, slope, rainfall intensity, and antecedent moisture conditions all influence runoff depth.

Q4: Are there limitations to this formula?
A: The formula assumes uniform infiltration rate and doesn't account for initial abstraction or varying rainfall intensity.

Q5: How is runoff depth used in practice?
A: It's used in hydrology for flood forecasting, designing stormwater management systems, and assessing water availability.