Related Questions

The scour depth D of a river during flood, may be calculated from the Lacey's equation
A D = 0.47 $$\left( {\frac{{\text{Q}}}{{\text{f}}}} \right)$$
B D = 0.47 $${\left( {\frac{{\text{Q}}}{{\text{f}}}} \right)^{\frac{1}{2}}}$$
C D = 0.47 $${\left( {\frac{{\text{Q}}}{{\text{f}}}} \right)^{\frac{1}{3}}}$$
D D = 0.47 $${\left( {\frac{{\text{Q}}}{{\text{f}}}} \right)^{\frac{2}{3}}}$$
V and R are the regime mean velocity and hydraulic mean depth respectively in meters. Lacey's silt factor f is
A $$\frac{{2{{\text{V}}^2}}}{{\sqrt 3 {\text{R}}}}$$
B $$\frac{{3{{\text{V}}^2}}}{{4{\text{R}}}}$$
C $$\frac{{5{{\text{V}}^2}}}{{2{\text{R}}}}$$
D $$\frac{{2{{\text{V}}^2}}}{{5{\text{R}}}}$$
According to Lacey, in regime conditions
A Silt is kept in suspension by vertical components of eddies
B Entire cross-section of the channel is generated at all points by the forces normal to the wetted perimeter
C Both (A) and (B)
D Neither (A) nor (B)
The Lacey's regime velocity is proportional to
A $${{\text{R}}^{\frac{1}{2}}}{{\text{S}}^{\frac{3}{4}}}$$
B $${{\text{Q}}^{\frac{3}{4}}}{{\text{S}}^{\frac{1}{3}}}$$
C $${{\text{R}}^{\frac{3}{4}}}{{\text{S}}^{\frac{1}{3}}}$$
D $${{\text{R}}^{\frac{2}{3}}}{{\text{S}}^{\frac{1}{2}}}$$
If D is the depth of scour below original bed, then the width of launching apron is generally taken as
A 1.2 D
B 1.5 D
C 2.0 D
D 2.5 D
The depth ‘d’ below the free surface at which the point velocity is equal to the average velocity of flow for a uniform laminar flow with a free surface, will be (where D is the depth of flow)
A 0.423 D
B 0.577 D
C 0.223 D
D 0.707 D
As per Lacey’s theory, the silt factor is
A directly proportional to average par¬ticle size
B inversely proportional to average par¬ticle size
C directly proportional to square root of average particle size
D not related to average particle size
Lacey's equation for calculating flood discharge in rivers, is
A $${\text{V}} = 10.8\,{{\text{R}}^{\frac{1}{2}}}{{\text{S}}^{\frac{1}{2}}}$$
B $${\text{V}} = 10.8\,{{\text{R}}^{\frac{2}{3}}}{{\text{S}}^{\frac{1}{2}}}$$
C $${\text{V}} = 10.8\,{{\text{R}}^{\frac{2}{3}}}{{\text{S}}^{\frac{1}{3}}}$$
D $${\text{V}} = 10.8\,{{\text{R}}^{\frac{1}{3}}}{{\text{S}}^{\frac{2}{3}}}$$
If average particle size of the silt in millimeters is m, the Lacey's silt factor f is proportional to
A m3
B $${{\text{m}}^{\frac{1}{2}}}$$
C $${{\text{m}}^{\frac{1}{3}}}$$
D $${{\text{m}}^{\frac{2}{3}}}$$
A river bend characterized by silting
A scouring on concave side
B silting on convex side
C scouring on convex side and on concave side
D scouring on concave side and silting on convex side

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