Costs of water-related infrastructure in adaptation have received attention at the global and regional level to bridge the 'adaptation gap' . For example,  estimated that subsidising capital costs to extend irrigation to its full potential would cost 0.13% of the GDP per year of low-and middle-income countries between 2015 and 2030. The coastal and riverine protection cost was between 0.06% and 1% of these countries' GDP per year over the same period. Projected economic damage due to coastal inundation was USD 169-482 billion in 2100 under RCP8.5-SSP3 without adaptation, but USD 43-203 billion cost to raise dike height will reduce 40% of the total damage . Hard infrastructure for river floods, costing $4-9 billion yr-1, can reduce damage by USD 22-74 billion yr-1 . Damages are estimated to be up to six-time larger than the cost of implementing efficient adaptation measures .  reported that investing USD 1.8 trillion globally, for example, in early warning systems, climate-resilient infrastructure; dryland crop production; mangrove protection; and improving the resilience of water resources between 2020 and 2030 could generate USD 7.1 trillion in benefits.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report