Assessing and mitigating risks to bridges from large wood using satellite imagery

The transport and accumulation of floating large wood (LW) debris at bridges can pose a major risk to their structural integrity. The impact forces arising from collisions of LW can cause significant damage to piers, while accumulations can constrict the flow and exacerbate scour at piers and abutments. Furthermore, LW accumulations increase afflux upstream of bridges, heightening the flood risk for adjoining areas. There is thus a need for a practical and rapid approach to identify bridges prone to LW-related hazards and prevent the formation of LW accumulations. Based on satellite imagery (SI), an approach is proposed to (a) quantify the risk of LW at a bridge structure and (b) locate a LW-trapping system upstream of the identified vulnerable bridge to dramatically reduce the risks of LW-related damage. The proposed methodology was applied to major rivers in Devon, UK. In this analysis, 26 bridges were identified as at risk to LW, with the majority prone to LW jams. Furthermore, SI was used to identify 12 locations for the potential installation of LW trapping systems for bridge protection. The results of this study show that SI is a powerful tool for the rapid assessment and planning of mitigation measures for bridges at risk to LW.