Discharge For Rectangular Channel Section Calculator

Formula Used:

\[ Q_e = A_{cs} \times \frac{R^{\frac{2}{3}} \times i^{\frac{1}{2}}}{n} \]

Area of Cross Section (A_cs):

m²

Hydraulic Radius (R):

Slope of Bed (i):

Manning’s Roughness Coefficient (n):

Environmental Discharge (Q_e):

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1. What is the Environmental Discharge Formula?

The Environmental Discharge formula calculates the rate of flow of a liquid in an open channel using Manning's equation. It considers the cross-sectional area, hydraulic radius, slope of the bed, and Manning's roughness coefficient to determine the discharge rate.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Q_e = A_{cs} \times \frac{R^{\frac{2}{3}} \times i^{\frac{1}{2}}}{n} \]

Where:

\( Q_e \) — Environmental Discharge (m³/s)
\( A_{cs} \) — Area of Cross Section (m²)
\( R \) — Hydraulic Radius (m)
\( i \) — Slope of Bed (-)
\( n \) — Manning’s Roughness Coefficient (-)

Explanation: The formula accounts for the channel geometry and surface roughness to estimate the flow rate of water in open channels.

3. Importance of Environmental Discharge Calculation

Details: Accurate discharge calculation is crucial for designing drainage systems, flood management, irrigation channels, and environmental impact assessments of water flow in natural and man-made channels.

4. Using the Calculator

Tips: Enter the cross-sectional area in square meters, hydraulic radius in meters, slope of bed (dimensionless), and Manning's roughness coefficient. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is hydraulic radius?
A: Hydraulic radius is the ratio of the cross-sectional area of flow to the wetted perimeter of the channel.

Q2: How is Manning's roughness coefficient determined?
A: Manning's coefficient depends on the channel material and surface conditions, with typical values ranging from 0.01 for smooth surfaces to 0.06 for rough natural channels.

Q3: What units should be used for slope?
A: Slope is typically expressed as a dimensionless ratio (e.g., 0.01 for a 1% slope).

Q4: Can this formula be used for pipes?
A: While Manning's equation is primarily for open channels, it can be adapted for partially full pipes with appropriate adjustments.

Q5: What are typical discharge values?
A: Discharge values vary widely depending on channel size and slope, from less than 0.1 m³/s for small streams to hundreds of m³/s for major rivers.