New Zealand researchers have called for the development of national flood maps after finding the country has $NZ135 billion ($127 billion) of building assets at risk from severe weather events.

Their river and storm flooding study shows almost 700,000 people and 411,516 buildings are at risk, along with extensive road and railway infrastructure and 20 airports.

National Institute of Water and Atmospheric Research (NIWA) hazard analyst Ryan Paulik says the study draws on local authority and government organisation information that varies in detail and age.

“National flood risk maps are essential,” he said. “We need accurate and comprehensive information about the impact and costs of flooding today and under different climate change scenarios so everyone can plan and adapt.”

Any specific event would affect only some of the exposed buildings, while potential direct and indirect economic losses are not considered by the NIWA and Deep South National Science Challenge report.

Risks for coastal areas have also been highlighted in a separate study released by the researchers that builds on previous work on rising sea levels by combining those impacts with 1-in-100-year storm tide events.

The study, which looks at changes in 10 centimetre increments, finds a 30-centimetre sea level rise would expose buildings worth $NZ18.49 billion ($17.44 billion) to flooding, up from $NZ12.5 billion ($11.8 billion) currently. A one-metre rise would increase the exposure to $NZ39 billion ($36.78 billion).

The Insurance Council of New Zealand says improved information on potential risks is important to insurers as well as property buyers and councils as they look at mitigation.

“Insurers take note of any modelling that can add to or broaden their current understanding of regional flood risks,” a spokeswoman told insuranceNEWS.com.au.