Scour Assessments

What are Scour Assessments?

Scour Assessments for structural assets are vitally important as flooding events become more prevalent. Stroma Specialist Access offers Inspection & Maintenance services for rail and highways bridges over rivers which may be more vulnerable to collapse through the scouring away of their foundations. Our Level 1 and Level 2 Scour Assessments can assess the local scour following floods and any potential damage to the structure.

Scour Assessments – Why choose Stroma Specialist Access?

Constriction scour and local scour on rail and highways bridges can lead to instability of the superstructure and potentially catastrophic outcomes. Stroma uses our IRATA qualified rope access inspection teams to survey the riverbed and its foundations. We can collect data to determine the risk ratings of surrounding structures. Following this inspection we can provide maintenance services to remove debris deposited during flood events to reinforce the safety of the structure.

Our expert service includes:

Calculation of Flow Depths and Velocities

Debris Removal

Level 1 Scour Assessments to BD97/12

Level 2 Scour Assessments

Preliminary Risk Rating

Riverbed and Foundation Surveys

Since 1990, Stroma has inspected over 1,000 structures on live railways and 3,000 disused rail structures. We have also undertaken inspections on trunk road structures for the UK’s leading contractors and numerous local authorities.

Scour Assessment Services

Level 1 Scour Assessments

Stroma can provide level 1 scour assessments to BD97/12 by surveying the riverbed, foundations and any existing protection measures and undertaking a preliminary risk rating.

Level 2 Scour Assessments

Depending on the outcome of the level 1 assessment, Stroma can also proceed to a level 2 assessment involving the calculation of flow depths and velocities under flood conditions resulting in the assignment of a Scour Risk Rating and recommendations for management measures. Our requirements from the client include:

Scour Assessment Services

  • Topographic survey of the bridge showing its key features (abutments, piers, arches, decks) and including cross-sections through the river channel upstream and downstream of the structure. The survey should include details of the bridge foundations (level) and any existing scour protection
  • Geotechnical information/boreholes/trial pitting of the bridge foundations to determine whether undercutting of abutments or piers is likely. This would also include obtaining the grading of granular materials forming the river bed
  • A hydrological analysis to determine extreme flows within the channel (usually based on Flood Estimation Handbook techniques) and a hydraulic model of the watercourse to determine the velocity of water running through the bridge structure during peak flow. We are able to undertake the hydrological analysis and hydraulic modelling if an existing hydraulic model is not available from the Environment Agency

Stroma can also remove the debris deposited during flood events, including when the river is in spate.

Why does scour occur?

The main cause of scour has been an increase in flood events as our climate has changed. This leads to instability of the superstructure and the outcome is the type of failure we saw at Feltham Railway Bridge in 2009, six separate road bridges in Cumbria also in 2009 and Tadcaster in 2015. Scour at bridge sites is typically classified as constriction scour and local scour. The former occurs across the cross-section of the bed on account of increased flow velocities associated with narrowing of the channel at the bridge site. Local scour is brought about by the increased velocities and vortices at abutments and piers. Debris struck at a crossing can exacerbate the effect by further constricting the channel.

Request a quote for Scour Assessment services

Contact our friendly I&M Team to request a quote for Scour Assessment.

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