through wider diameter drainage pipes or trenches costs a small percentage of the road’s value, while increasing the flood resilience of a railway by elevating it costs 50 percent of its value. And protecting a hydropower plant against earthquakes by installing the proper anchorage and seismic components costs 20 percent of its value, whereas protecting a hydropower plant against flooding through bigger spillway capacity costs only 3 percent of its value (Miyamoto International 2019).

Improved quality control is required to ensure that an asset is built and maintained to expected standards. Miyamoto International (2019) estimates that this quality control costs from 1 percent to 5 percent of the value for most assets and hazards, but it can cost up to 15 percent (e.g. ensuring that drainage systems can cope with earthquake motion, and that highway systems can cope with flooding). This quality control would accompany the good procurement practices that are key to lower infrastructure construction costs.

The options explored in Miyamoto International (2019) have been selected because they are realistic, and can make assets more resilient in low‐ and middle‐income countries. However, they are not necessarily the ones that will reduce risk the most, and they do not guarantee that assets cannot be damaged by natural hazards. Many rich countries like Japan implement technical solutions that go beyond—and are more expensive than—the set of solutions considered in this analysis.

# The cost of increasing resilience

The next question then becomes, by how much would estimates of future infrastructure investment needs change if infrastructure systems were designed and built in a more resilient manner, through the technical and engineering solutions identified in Miyamoto International (2019)?

To answer this question, we take the infrastructure spending scenarios developed by Rozenberg and Fay (2019) and for each asset type, each hazard, and in each scenario, we apply the incremental cost of resilience given by Miyamoto International (2019). For example, in the transport sector we apply a different incremental cost of flood resilience for airports, railways, urban public transit, highways, or rural roads. The overall cost of resilience will thus depend on the types of investments in the initial scenario (a scenario that represents an investment shift towards more rail will have a higher resilience cost than a scenario where transport investments are focused on roads). As a consequence, we present a range of resilience costs that comes from the range of possible infrastructure spending in Rozenberg and Fay’s scenarios.

For each scenario we also assess the overall risk reduction associated with these investments, still using the estimates given by Miyamoto International (2019). Here, again, the benefits depend on the type and quantity of infrastructure investments that are realized.

Because the incremental costs of making assets more resilient can be significant, it is important to target strengthening to areas where exposure to natural disasters is high. Ideally, infrastructure standards and codes should be asset and localization specific. Any effort to design a road should account for the hydrological and hydraulic data and climate model results at the location of the road in order to include in the design the range of impacts that climate change can have on the probability of flood events in the future. For electricity distribution systems—because they are particularly vulnerable to wind from storms, hurricanes, and typhoons—historical data and model results on wind velocities with hour‐level 4