Free · Railway Engineering

Railway Bridge Maximum Scour Depth Calculator

IRS Bridge Sub-structure & Foundation Code practice — Lacey normal scour or constricted-channel method, maximum scour by river condition, and a foundation depth safety check.

Bridge Data

Bridge No. / location

Existing / estimated discharge, Q (m³/s)

Catchment area (km²)Used for the Clause 4.4 discharge increase.

Bed Condition

Bed type

Bed material / silt factor

Hydraulic / Scour Method

Scour calculation method

Effective waterway width, B (m) qf = Qf / B

Discharge intensity qf (optional)

Clause 4.6.3: D = 0.473 × (Qf / f)^(1/3)
Clause 4.6.4: D = 1.338 × (qf² / f)^(1/3)

Maximum Scour & Safety Check

River condition

Existing / proposed curtain wall or foundation depth below bed (m)

Water level RL for Qf (optional, m)

Clause 4.4 increase—

Foundation design discharge Qf—

Silt factor f—

Discharge intensity qf—

Normal scour depth D—

Maximum scour depth—

Available foundation / curtain depth—

Margin against calculated scour—

Scour level RL—

Enter the bridge data and click Calculate.

Code reference values

Local river condition	Maximum scour depth
Straight reach	1.25D
Moderate bend / apron of guide bund	1.50D
Severe bend	1.75D
Right-angle bend / nose of pier	2.00D
Severe swirls	2.50D to 2.75D

Engineering aid Verify current correction slips, actual site conditions, approved hydraulic data and competent-authority requirements before final adoption.