Lacey''s silt factor (f) for regime channel design is given by:
Choose the correct answer
f = 1.76 × m_r
f = 1.76√(m_r) where m_r = mean particle size in mm
f = √(m_r)/1.76
f = 0.447 × m_r
Correct Answer
B. f = 1.76√(m_r) where m_r = mean particle size in mm
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Lacey''s silt factor f = 1.76√(m_r) where m_r = mean particle size of silt in mm. For standard silt (m_r = 1 mm): f = 1.76. f is used in Lacey''s regime equations: velocity V = 0.447√(fR), R = hydraulic mean radius. Coarser silt → higher f → steeper gradient and narrower section.
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