Floodwater can remove material around a bridge foundation while leaving the deck and approaches looking comparatively intact. For the team assembling a post-flood record, the immediate question is what has changed since the last reliable observation and what remains hidden. A defensible record helps the asset owner decide whether further investigation is needed and gives the next inspection team something reliable to compare.
Start with the waterway and the foundation
Scour is the removal of bed or bank material by flowing water. At a bridge, it can occur around individual piers or abutments, where the crossing constricts the channel, or alongside broader changes in bed level and channel position. These processes can occur together. A local hole near a pier may be the most visible sign, while a change in channel alignment upstream may help explain why flow now approaches that pier differently.
Start the desk review with the as-built foundation drawings, previous inspection photographs, available bed profiles and the asset owner’s flood response procedure. Establish whether the bridge is supported on shallow footings or piles and record where that information came from. If drawings are missing or unreliable, mark foundation details as unknown. Avoid estimating embedment from what can be seen above water.
Make repeat observations comparable
A post-flood photograph is far easier to interpret when its viewpoint, direction and location are recorded. Identify the bridge, span, pier or abutment consistently with the asset register. Take overview photographs that establish the channel context, then detail views of any exposed foundation, displaced protection or erosion at the approach. Record the time, water level reference where available, and visibility. A photograph of cloudy water still has value if its limitations are clear.
Where an authorised survey is undertaken, ask for the coordinate and height reference, the survey date and enough information to relate the measurements to earlier sections. For example, two bed elevations measured beside the same pier may show a difference because of a genuine change in bed level, a different measurement location or a different vertical reference. Keeping those details with the result makes the comparison reviewable.
Record uncertainty alongside the observations
Describe the observed condition separately from the explanation. A useful record might say that rock protection is visibly displaced at the downstream end of an abutment and that the footing could not be inspected below the current waterline. The first statement is evidence. The second tells the reviewer where evidence is missing. Scour holes can also partially refill as flows recede, so a later bed profile may fail to capture the deepest erosion during the event.
Access and assessment should follow the asset owner’s incident procedures. Field teams should document what they could observe from authorised locations and refer submerged areas, suspected movement or uncertain foundation conditions for specialist assessment. A clean-looking road surface or a single depth reading cannot establish the overall condition of a crossing.
Give the asset owner a record that supports the next decision
A concise handover brings together the latest observations, comparisons with baseline data, known limitations and items requiring follow-up. Include a plan or marked-up photograph to locate the evidence. Where an issue is referred onward, name the responsible role and retain the decision and its supporting information with the inspection record. Reopening and any restrictions are decisions for the authorised asset owner under its procedures.
For Australian bridge teams, Austroads’ 2025 waterway design guide covers scour assessment, monitoring and countermeasures. Queensland Department of Transport and Main Roads publishes additional criteria and exceptions for its own practice. Confirm which documents the asset owner adopts before applying assessment criteria. Austroads Guide to Bridge Technology, Part 8 · Queensland Bridge Scour Manual
Watch: Scour assessment explained
For further technical context, Australian Water School’s Advances in scour assessment webinar discusses assessment at bridge piers and abutments, hydraulic modelling and the FHWA hydraulic toolbox. It complements the inspection-record guidance above with a broader look at scour analysis.
Video source and supporting materials: Australian Water School. Watch on YouTube.
Scour monitoring at a bridge pier in South Carolina. Illustrative photograph. U.S. Geological Survey, South Atlantic Water Science Center · Public domain.
