Runoff Coefficient and Volume Calculator
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Historical Background
The coefficient of runoff (C) is a key factor in hydrology used to measure how much rainfall contributes to surface runoff rather than infiltrating into the soil. The concept has been in use for over a century, helping engineers design stormwater management systems, flood control measures, and irrigation planning.
Calculation Formula
The coefficient of runoff is calculated using the formula:
\[ C = \frac{\text{Volume of Runoff}}{\text{Volume of Rainfall}} \]
If two values are known, the third can be determined using:
\[ \text{Volume of Runoff} = C \times \text{Volume of Rainfall} \]
\[ \text{Volume of Rainfall} = \frac{\text{Volume of Runoff}}{C} \]
Example Calculation
If the coefficient of runoff is 0.6 and the volume of rainfall is 500 m³, then the runoff volume is:
\[ \text{Volume of Runoff} = 0.6 \times 500 = 300 \text{ m³} \]
If the runoff volume is 300 m³ and the rainfall volume is 500 m³, then the coefficient of runoff is:
\[ C = \frac{300}{500} = 0.6 \]
Importance and Usage Scenarios
- Urban Drainage Systems: Helps in designing stormwater drainage to prevent flooding.
- Agriculture and Irrigation: Determines water loss and efficiency in farmlands.
- Environmental Engineering: Assists in assessing water retention and groundwater recharge.
- Flood Risk Management: Aids in predicting the impact of heavy rainfall on different terrains.
Common FAQs
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What is a typical runoff coefficient?
- It varies depending on the surface type. For example, grasslands have a low runoff coefficient (~0.1-0.3), while concrete surfaces have a high coefficient (~0.7-0.9).
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Why is the coefficient of runoff important?
- It helps engineers and hydrologists determine how much rainfall becomes runoff, which is critical for water resource management and flood control.
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Can the runoff coefficient exceed 1?
- No, the maximum value is 1, which means all rainfall turns into runoff with no infiltration.
This calculator provides an easy way to compute the coefficient of runoff or determine runoff volume, making it a valuable tool in hydrology and environmental engineering.