transportation. In addition, between $550 billion and $700 billion would be needed every year to maintain the existing and new transport infrastructure in low‐ and middle‐income countries by 2030, bringing the total annual spending needs to between $700 billion and $1.8 trillion. How would those costs increase to make transport systems more resilient?

- _Scenario 1._ The incremental cost of making new exposed transport assets more resilient to floods and landslides lies between $860 million and $35 billion depending on the baseline spending scenario. This is a 0.6 percent increase in cost on average across the spending range and potentially a 5 percent increase in the most expensive case. These investments would reduce the risk of damage for new infrastructure by a factor of two.

- _Scenario 2._ If instead all new transport assets were made more resilient to floods and landslides regardless of their exposure, the incremental cost would be from $8 billion to $350 billion a year. This is a 5.5 percent increase in cost on average across the spending range, but potentially a 17 percent increase in the most expensive case for many rail investments.

# Water and sanitation

In the water supply and sanitation sector, the cost of providing universal access to safe water and sanitation in low‐ and middle‐income countries by 2030, with the current resilience level, would range from $116 billion to $229 billion a year for capital investments and from $32 billion to $69 billion a year for maintenance. How would those costs increase to make water and sanitation systems more resilient?

- _Scenario 1._ The cost of protecting new exposed water assets would be between $0.9 billion and $2.3 billion a year (assuming that on average water and sanitation infrastructure has the same exposure to earthquakes as transport and power assets). These investments would reduce the risk of damage to new infrastructure by 50 percent.

- _Scenario 2._ Instead, if all water assets were made more resilient to floods, an additional $2 billion to $5 billion a year would be required. This estimate represents a 1.1 percent to 2.2 percent increase in capital costs. Increasing the resilience of these assets to earthquakes would require an additional $8 billion to $20 billion a year (or between 5 percent and 9 percent of capital investment needs).

# Summing up

Unfortunately, similar estimates were not possible for telecommunications, and these numbers only include low‐ and middle‐income countries. Yet this exercise provides two important insights.

_First, there is huge value in knowing the spatial distribution of natural hazards, including climate change._ Focusing the strengthening of infrastructure assets on exposed assets reduces total annual costs from between $120 billion and $670 billion to between $11 billion and $65 billion (figure 1). The savings from targeting the infrastructure assets most exposed appear to be orders of magnitude larger than the costs of data collection and modeling that would be required to improve knowledge of current and future hazards. Indeed, a global platform like Think Hazard! (Fraser 2017) costs a few million dollars to create and maintain. At most, creating high‐resolution digital elevation models and hazard maps for all cities in low‐ and middle‐income countries would cost a few hundred million dollars (Croneborg et al. 2015).

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