Nabin Kumar Ijam | Civil & Hydropower Engineer

SCOUR DEPTH CALCULATION

INPUTS

Flood discharge (\(Q\) in m³/s):

River width (\(L\) in m):

Select the silt size according to the following table

Material Type	Fineness	Size of material
Silt	Very fine	0.05 to 0.08
	Fine	0.12
	Medium	0.16
	Standard	0.32
Sand	Medium	0.51
Sand	Coarse	0.73
Bajri and sand	Fine	0.89
	Medium	1.29
	Coarse	2.42
Gravel	Medium	7.28
Gravel	Heavy	26.10
Boulder	Small	50.10
	Medium	72.50
	Large	188.80

Average grain size in mm (\(d_m\) in mm):

Consideration of seismic condition:
Structure:

DESIGN RESULT

	Symbol	Formula	Value	Unit	Clause
Silt factor	\(f\)	\(f=1.76(d_m)^{0.5}\)			703.2.2
Scour depth from Flood level	\(R\)	\(R=1.35(\frac{q}{f})^(\frac{1}{3})\)		m	703.2
Minimum scour depth	\(R_{min}\)			m	703.3.1
Scour depth	\(R_a\)			m