Delta Life 12

14 Building robust railways Climate change can impact transport by water and by rail. But not equally disastrously everywhere and – more importantly – in different ways depending on the type of transport. Deltares identifies the bottlenecks, making timely intervention possible. Charting risks ProRail is responsible for the railway network in the Netherlands and that network is reaching the limits of possible growth. The network is used intensively by ever-higher numbers of passenger and freight trains. The in­ creasing physical strain on the railways is putting pressure on quality. The 'soft' Dutch subsurface means that mainte- nance is already required much more often than with a firm subsurface, argue Joris van Ruijven and Mike Woning of Deltares. Put climate change into the mix and it is clear that we have a real challenge on our hands. Deltares is mapping out the risks for ProRail and developing new techniques to meet this challenge. Charting the structure of the Dutch subsurface makes it possible to identify the risks for rail- ways. Combining this information with data about the loads imposed by trains makes it possible to identify vulnerable locations where additional maintenance is required. And railways are also threat­ ened by water-related factors: rainwater drainage, rising groundwater and flooding. Each of these threats requires a different approach to detection. Problems for travellers or carriers Existing flood maps can be used to identify where the railways are sus­ ceptible to flooding from the coast and major rivers. It is more difficult to assess the risks associated with rainwater. That requires mapping out elevation differences accurately (because water flows to the lowest point). Deltares uses risk profiles to sketch the risks in outline first before moving on to more accurate descrip­ tions. These profiles show that railways in urban areas are particularly sensitive to extreme weather. Finally, hydrolo- gical models are used to map out the risks associated with rising ground­ water. For example, locations have been identified where the combination of high water tables and precipitation can lead to subsidence or softening in the subsurface, problems that can result in damage to the infrastructure or diffi- culties for passengers or carriers. That makes it important to determine the impact of the climate in conjunction with information about the condition of the infrastructure. Drafting scenarios The question now is how to deal with risks of this kind: can the impact of climate change and additional maintenance be taken into account in, for example, investment decisions? Ideally, the costs of adaptation should be calculated now but the future is also uncertain for Van Ruijven en Woning. There are two factors that make predictions so difficult: how will the climate behave and how will the railway network develop? Working up hypotheses ('what if?') makes it possible to establish scenarios with the aim of preventing problems. For more information: joris.vanruijven@deltares.nl mike.woning@deltares.nl RAILWAYS DOSSIER ROBUST INFRASTRUCTURE