Curb gutter Longitudinal Slope formula |
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\( m_l \;=\; \left( \dfrac{ Q \cdot n }{ 0.56 \cdot m_c^{5/3} \cdot q^{8/3} } \right)^2\) (Curb Gutter Longitudinal Slope) \( Q \;=\; \dfrac{ 0.56 }{ n } \cdot m_c^{5/3} \cdot m_l^{1/2} \cdot q^{8/3} \) \( n \;=\; \dfrac{ 0.56 }{ Q } \cdot m_c^{5/3} \cdot m_l^{1/2} \cdot q^{8/3} \) \( m_c \;=\; \left( \dfrac{ Q \cdot n }{ 0.56 \cdot m_l^{1/2} \cdot q^{8/3} } \right)^{3/5}\) \( q \;=\; \left( \dfrac{ Q \cdot n }{ 0.56 \cdot m_c^{5/3} \cdot m_l^{1/2} } \right)^{3/8} \) |
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| Symbol | English | Metric |
| \( m_l \) = Longitudinal Slope of Pavement | \(dimensionless\) | - |
| \( Q \) = Gutter Flow Rate | \(ft^3 \;/\; sec\) | - |
| \( n \) = Manning's Roughness Coefficient | \(dimensionless\) | - |
| \( m_c \) = Roadway Cross Slope | \(dimensionless\) | - |
| \( q \) = Flow Width | \(ft\) | - |
Curb gutter longitudinal slope, also called incline or gradient of the gutter along its length, running parallel to the adjacent curb. It is a design element for effective stormwater drainage along roadways. This slope, typically expressed as a percentage, ensures that water collected in the gutter flows towards designated outlets such as inlets or catch basins. A sufficient longitudinal slope is essential to prevent ponding, reduce the spread of water onto the travel lanes, and minimize the risk of hydroplaning, ultimately contributing to safer driving conditions. The design value of this slope considers factors like rainfall intensity, gutter cross slope, and the desired flow capacity to efficiently manage stormwater runoff.
