ABSTRACT
Weather-related disruption is a pressing issue for road and rail networks across the globe. In many cases such disruption can be expected to be aggravated due to climate change. One climate-related risk for bridges is bridge scour, the removal of riverbed material at the foundations of the structure due to hydraulic action. Scour is the foremost cause of bridge failure worldwide; this highlights the need to understand the relationship between climatic drivers and scour risk. Global climate change affects local weather patterns, which results in changes in river flow regimes. This can affect scour depths and the risk of bridge failure.
At the same time the quality of data used in some scour assessments can be variable. Bridge owners across the world often manage vast bridge stocks. Collecting robust data and maintaining rigorous records at such large scales is challenging and some inaccuracies in the data may be introduced, which reflect on the outcome of scour assessments.
This paper presents a study of the sensitivity of a scour risk model to all model inputs, with a focus on the link between scour risk and climatic drivers. The selected risk model is used in the railway industry in Great Britain and is focused on the prioritisation of vulnerable structures. The study is based on a group of twenty-eight bridges over rivers in Great Britain. The effects of climate change are simulated by varying flow conditions over a wide range of values. An assessment of the sensitivity to all model inputs reveals the most influential variables in the analysis.
Results indicate that variations in river flows due to climate change are not as influential as potential variations in some of the characteristics of the structure. Thus, even the high uncertainties, which characterise future climate change and its effect on river flows, would have a relatively low impact on the final estimate of bridge scour risk for railway bridges.
The model is most sensitive to variations in foundation depth. This variable is often associated with high uncertainties, especially in the case of old structures, where record information may not be available. The risk model is also highly sensitive to variations in the width of piers and abutments and to the angle of attack for piers. Improving the quality of data for such inputs can improve the quality of a scour risk assessments and bring it closer to the full potential of the selected scour risk model.
Although uncertainties in climate projections can be very high, reducing the uncertainty in the most sensitive model inputs would have a more significant impact on the overall risk estimate than reducing the uncertainties in climate projections.
The increased understanding of the link between various drivers, including climatic drivers, and bridge scour risk is a fundamental step towards increasing bridge resilience to current and future climate and thus is an important aspect of climate change adaptation.
