The one-two punch of tropical storms Irene and Lee in 2011 has prompted New York City to spend an additional $70 million to reduce flood hazards that threaten its water supply.

The city will earmark at least $15 million through 2017 to buy vulnerable homes and businesses, including those not eligible under the Federal Emergency Management Agency's flood buyout program. Local communities must sign off on any city purchases.

The city also will provide $17 million for flood mitigation in those communities.

The programs were finalized this month under changes to a federal waiver that allows New York City to avoid filtering its drinking water from west of the Hudson River.