Lloyd’s has outlined key lessons from last year’s devastating storms as it prepares for the new Atlantic hurricane season, which started last Friday.

It says insurers must remember that each hurricane is unique and surprises are always possible, even for “well-modelled” risks, meaning the best-laid plans often go awry.

Hurricane Harvey last August brought widespread flooding caused by extreme rain, which was not predicted in the modelling.

“The sheer scale of devastation last year was another issue,” Lloyd’s says.

“The fact that three hurricanes made landfall within a matter of weeks led to additional costs due to shortage of building materials, driving up costs and causing delays in rebuilding.

“This is a factor insurers should consider more closely when underwriting risks in future.”

The $US200 billion ($264 billion) of economic losses from hurricanes Harvey, Irma and Maria have exposed the need for greater private sector participation in the US flood insurance market, Lloyd’s says.

The London market is working with government leaders, industry bodies and distribution partners in the US to drum up private sector interest.

“Greater participation of private market insurers could lead to higher resilience and increased insurance penetration,” Lloyd’s says. “As well as developing a better-functioning flood insurance market, this could help by highlighting the risk of building in certain areas.”